Session - Observing and predicting space weather driven ionospheric disturbances:
observational networks and modeling techniques, new services and
mitigation procedures
Matthew Angling, Anna Belehaki, Manuel Hernandez-Pajares and Ioanna Tsagouri
The ionosphere is a region of the upper atmosphere that is ionized
primarily by solar radiation. Variations in solar activity and in the
near-Earth environment can severely disturb the density of the
ionosphere. This, in turn, can affect a wide range of radio systems on
which European societies and economies are increasingly dependent, such
as Galileo and EGNOS. The session will focus on contributions concerning
new tools for modelling and forecasting the ionosphere and new services
that can be applied to improve the operation of radio systems. More
specifically we welcome papers on the modelling of space weather
disturbances in the bottomside ionosphere and their impact in the plasma
redistribution in the topside ionosphere and plasmasphere; nowcasting
and forecasting techniques including data assimilation and empirical
models and their validation; nowcasting methodologies for identifying
and tracking Travelling Ionospheric Disturbances; topside reconstruction
techniques using vertical electron density and radio occultation data
from satellite missions; presentation of new services and software tools
that exploit the output of forecasting models to support operational
systems; development of mitigation procedures to protect critical
infrastructures from space weather driven ionospheric effects;
presentation of relevant national and international activities and
projects.
Talks and First Class Posters
Wednesday November 19, 09:00-11:00, 11:30-13:00, auditorium Rogier
Poster Viewing
Wednesday November 19, 11:00-11:30, area in front of auditorium Rogier.
Talks and First Class Posters
| 9:00 am |
Using the Spectral Response of
Space-Borne Instruments in Flare Conditions for the Modelling of
Flare-Induced Ionization Rate in the Lower Ionosphere. |
| |
Dominique, M1; Zigman, V2 |
| |
1Royal
Observatory of Belgium; 2University of Nova Gorica |
| |
We estimate the electron-ion
ionization rate of the lower ionosphere, the D-region (50-90 km height),
during solar X-ray flares, induced by the severely enhanced solar irradiance,
I [Wm^-2], as detected by instruments on-board several satellite missions, e.g. GOES, SDO, PROBA2 in different
corresponding wavelength bandpasses from hard X-ray to EUV. To model how the irradiance time evolution
during flares affects the ionosphere, the so-called local ionization
efficiency, k [1/Jm], (i.e. the number
of electron-ion pairs produced per unit energy per unit path length) is
needed. This quantity is clearly wavelength-dependent, and therefore needs to
be estimated separately for each instrument as a function of its bandpass. It
also varies with altitude, as does the composition of the constituent-rich
lower ionosphere. To obtain a
realistic estimate of k, the knowledge of the spectral irradiance I_lambda,
[Wm^-2 nm^-1] during flares is needed, a quantity which is not always
available and only provided for limited parts of the spectrum. To circumvent
this difficulty we are using the synthetic specific irradiance I_lambda_Omega
[Wm^-2 nm^-1 sr-1] provided by the CHIANTI model. Preliminary results of CHIANTI when
applied to several specific flares and their particular temperature dependent
DEM show severe variations of the spectral irradiance contribution during
flares with respect to quiet conditions.
The first examinations of the flare response of the radiometer LYRA
on-board of PROBA2 in the Zr channel 2-4 and at wavelengths relevant for
ionization at 90 km height, indicate that in the low bandpass < 2nm, (i.e. between 1 and 2 nm) the
irradiance is about two orders of magnitude higher than in the 6-9 nm
bandpass. In contrast, at quiet Sun conditions, the higher bandpass dominates
over the lower one, the irradiance being by a factor of 3 higher. We plan to apply our procedure to different
instruments to determine how the various parts of the solar spectrum
contribute to their nominal bandpasses during flares and the pertaining local
ionization efficiency at different heights during flare occurrence. |
| 9:20 am |
Solar Activity Parametrisation
for OPTIMAP |
| |
Bothmer, V1; Schmidt, M2; Bosman, E1; Dettmering, D2; Limberger, M2; Venzmer, M1 |
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1University
Göttingen; 2DGFI |
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OPTIMAP (OPerational Tool for
Ionosphere Mapping And Prediction) is a German project aiming at providing
advanced predictions of ionospheric VTEC conditions in near real-time up to
several days in advance. Here we summarise the key data sets and scientific
analysis methods used to derive those solar activity parameters that are
crucial for the OPTIMAP forecasts. The
OPTIMAP near real-time analysis of solar conditions bases on data from the
SDO, STEREO, Proba2, SOHO and ACE satellites and complementary ground-based
data sets. The derived metadata describe the quasi steady state solar wind
flow and global EUV emission, and the
impact of superimposed transient coronal processes in form of flares
and CMEs. |
| 9:40 am |
Comparison of Modelled and
Observed Ionospheric HF Radio Propagation over the Polar Cap in Response to
Solar Flares and a Weak CME of January 2014 |
| |
Hallam, J1; Stocker, A1; Warrington, M1; Siddle, D1; Zaalov, N2; Honary, F3; Rogers, N3; Boteler, D4; Danskin, D4 |
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1University
of Leicester; 2St. Petersburg State University; 3University of Lancaster; 4Geomagnetic Laboratory, Geological Survey of Canada |
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Space weather events can have a
range of disruptive effects on the ionosphere, especially in the polar cap.
This region is of growing importance for intercontinental air travel, lying
across the shortest path between significant destinations, e.g, Washington-Beijing.
Following these great-circle routes is increasingly desirable as travel time,
cost and pollution is reduced. However, in the polar cap geostationary
satellites lie below the horizon and both geographic and geopolitical
considerations mean there are at best limited VHF radio air-traffic control
facilities. Thus HF radio propagation via the ionosphere is of critical
importance in maintaining communications with aircraft flying transpolar
routings. Hence adverse space weather conditions, leading to ionospheric
disruption which in turn affects HF radio propagation is of critical
importance when considering whether a polar routing is viable in the days and
hours in advance of a flight. The most
severe space weather events lead to a total loss of communications (i.e.
radio blackout) via absorption. More common events of intermediate severity
can lead to disruption of communications. Typically the HF signal will
propagate on a great-circle path between transmitting ground station and
receiving aircraft. The presence of patches of enhanced ionospheric electron
density can shield particular regions from a given transmitter site, and may
also reflect the transmissions into unexpected areas. Thus an appropriate
choice of transmitter location and frequency is critical for good
ground-aircraft communications. As
part of a significant international project our work is to determine the
current condition of the ionosphere from limited data (‘nowcasting’), and
estimate how it will evolve in the several hours-long duration of a flight
('forecasting'). To achieve this we use our dynamic ionospheric raytracing
model, in conjunction with HF sounding and other geophysical measurements.
Inclusion of real-time space weather data from other sources potentially
allows this approach to be used for true, albeit short-term, forecasting -
both in terms of knowing if communications will be blacked-out by an event,
and predicting when communications will become possible again. In this paper we present the effect of an
‘intermediate’ event - a series of M and X class solar flares and a
relatively weak CME on HF radio performance from 6 to 13 January 2014.
Significant ionospheric effects were observed during this event, but - aside
from a short period - were not sufficient to produce a radio blackout. A
ray-tracing model with a realistic background ionosphere based on
observation, D-region absorption inferred from satellite measurements (DRAP)
with inputs from real-time measurements, riometer data,
HF-transmitter/receiver antenna patterns and including localised ionospheric
features (e.g. polar patches and arcs) is used to predict radio propagation behaviour.
This modelled behaviour is compared with the observed HF radio signal on six
paths (one entirely within the polar cap, three trans-auroral, and two
sub-auroral). |
| 10:00 am |
Global Ionosphere Redistribution
during the Main Phase of Geomagnetic Storm on 29-31 August 2004 |
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Astafyeva, E1; Zakharenkova, I1 |
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1IPGP |
| |
It is known that propagation of
global navigation satellite systems (GNSS) signals depends directly on the
state of the ionosphere, since intensive irregularities and/or gradients of
electron density modify the parameters of propagating waves. Ionospheric
perturbations during geomagnetic storms are known to be the major source of
such intensive ionospheric irregularities, indicating large impact on
GPS/GNSS performance. Besides intense geomagnetic storms and super-storms,
weaker events, especially during periods of low solar activity, can also
generate very strong ionospheric disturbances. In this work, we use multiple
ground-based and space-borne instruments to study global redistribution of
ionospheric plasma during moderately intense storm of 29-31 August 2004.
Despite the storm was far from the strongest events in the 23 solar cycle, it
provoked sufficiently large effects in the ionosphere. During the main phase
of the storm, signatures of a strong positive storm were observed over a very
large range of longitudes, from pre-dawn to midnight local sectors.
Simultaneously, very strong negative storm occurred in a narrow longitudinal
sector from midnight to ~6LT. Data from satellite altimeters TOPEX and
Jason-1 and from CHAMP satellite showed significant storm-time enhancement of
the equatorial ionization anomaly (EIA) in the post-sunset sector. Because
the altimeters and the CHAMP satellite crossed the equator at the same local
region, we could estimate the contribution of the topside ionosphere. Further,
we use in-situ data from CHAMP and DMSP satellites, as well as data from
CHAMP onboard and ground-based GPS-receivers to study occurrence and global
distribution of ionospheric irregularities during the main phase of the 29-31
August 2004 storm. Our results reveal occurrence of two main regions with
intense ionospheric irregularities: 1) high-latitudes on both day and
night-sides in both hemispheres during the main phase of the storm, and 2)
low-latitudes of the Atlantic sector on the dusk and pre-midnight at the end
of the main phase of the storm. In southern hemisphere, fluctuations of
high-latitude ionospheric plasma density and, consequently, of GPS ROTI, are
found to be stronger than that in northern hemisphere. To our knowledge, this
is the first-time observations of phase fluctuations from GPS-receiver
onboard LEO satellite. |
| 10:20 am |
Monitoring Irregularities in the
Mid-Latitude Ionosphere Using HF Radars |
| |
Menk, F1; Waters, C1; Devlin, J2 |
| |
1University
of Newcastle; 2La Trobe University |
| |
An international consortium of
dual over-the-horizon radars has operated for many years in order to
investigate and provide maps of ionospheric convection at high
latitudes. Called SuperDARN, this
network now comprises over 30 radars covering the auroral, polar cap and
sub-auroral regions. In particular,
three radars operated by an Australian collaboration provide high spatial and
temporal monitoring of the mid-latitude ionosphere in the vicinity of the
projection of the plasmapause.
Observations show Doppler shifts due to motions arising from
reflections from field-aligned structures and vertical motions in the
ionosphere. In fact we find that the
mid-latitude ionosphere hosts a variety of irregularities and features under
both quiet and disturbed conditions.
Features such as convective flows, reconnection and storm-associated
drifts, travelling ionospheric disturbances and other irregularities
including those produced by magnetospheric ULF plasma waves, are readily
observed. We present examples
illustrating the capability of these instruments and some of the more
enigmatic features they detect, and discuss such observations in terms of
operational systems and the development of mitigation procedures. |
| 10:40 am |
Identification and Tracking of
Travelling Ionospheric Disturbances Exploring Ground-Based Ionograms and 3D
Electron Density Distribution Maps |
| |
Belehaki, A1; Kutiev, I2; Tsagouri, I3; Marinov, P4 |
| |
1NOA;
2Bulgarian
Academy of Sciences and National Observatory of Athens; 3National Observatory of
Athens; 4Bulgarian
Academy of Sciences |
| |
The ionosphere is a region in
the near-Earth space where a number of operations take place. These
operations are important for the daily life and the safety of the citizens:
telecommunication systems, navigation and surveillance systems, aircraft
safety systems, all rely on signals propagating in the ionosphere and through
the ionosphere. Therefore it is important to continuously monitor the state
of the ionosphere and be able to predict irregularities and disturbances,
that may affect the operation of these critical systems. The ionosphere is affected by solar
disturbances (space weather effects) and by other natural hazards
(earthquakes, tsunamis, hurricanes, strong tropospheric convection) or
artificial phenomena (nuclear explosions, and other powerful blasts like
industrial accidents). All these phenomena are manifested as waves travelling
in the ionosphere. Current identification techniques of Travelling
Ionospheric Disturbances (TIDs) rely on the analysis of vertical TEC values
derived from slant TEC measurements from the ground-based GPS receiver
network. In this contribution we are exploring a different approach for the
identification and tracking of TIDs over a specific world area, based on the
combined analysis of 3D Electron Density Distribution maps calculated with
the Topside Sounders Model Profiler (TaD), on the analysis of ionograms from
Digisondes and on the statistical analysis of TEC data from GNSS receivers.
The first results indicate the need to set up criteria able to indentify
medium scale from large scale TIDs, and to further improve the increase the
sensitivity of the Topside Sounders Model Profiler in disturbances originated
by TIDs. |
| 11:30 am |
A Comparison of Scintillations
with Forecasts in the GNSS bands at Jicamarca, Peru |
| |
Zürn, M1; Anderson, D2; Fortuny Guasch, J3 |
| |
1European
Commission · Joint Research Centre; 2NOAA; 3JRC |
| |
A Comparison of Scintillations
with Forecasts in the GNSS bands at Jicamarca, Peru David Anderson (NOAA), Martin Zurn (JRC),
Joaquim Fortuny Guasch (JRC) The
scintillation phenomenon over tropical areas may have a negative effect on
GNSS. It is critical to have knowledge of the current ionospheric conditions
so that system operators can distinguish between the natural radio
environment and system-induced failures. We describe a technique for
forecasting UHF scintillation activity in the equatorial region after sunset
and compare these forecasts with observed GNSS bands near 1.2 and 1.6 GHz at
Jicamarca, Peru on a night-to-night basis.
The technique (See Redmon et al., Space Weather, Vol 8, 2010) utilizes
the observed characteristic parameter h’F from a ground-based ionosonde near
the magnetic equator. There is an excellent correlation between h’F at 1930LT
and the pre-reversal enhancement in vertical ExB drift velocity after sunset
which is the prime driver for creating plasma depletions and bubbles. In
addition, there exists a “threshold” in the h’F value at 1930 LT, h’F_thr,
such that, on any given evening if h’F is significantly above h’F_thr then
scintillation activity is likely to occur and if it below h’F_thr,
scintillation activity is unlikely to occur. The digital sounder at
Jicamarca, Peru provides the h’F values between 1830 and 2000 LT and the JRC
multi-constellation receiver at Jicamarca provides the observed scintillation
activity Index, S4 values night-to-night during the during the period around
the first equinox of the year 2014. |
| 11:50 am |
Spatial Statistics Performed on
Multi-GNSS Measurements for the Analysis of Spatio-Temporal Characteristics
of Equatorial Ionospheric Scintillations |
| |
Lonchay, M1; Wautelet, G1; Cornet, Y1; Aquino, M2; Warnant, R1 |
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1University
of Liège; 2University
of Nottingham |
| |
The ionosphere has always been a
major limitation for GNSS positioning applications. Free electrons in the
ionosphere perturb the propagation of GNSS radio signals involving both
refraction and diffraction effects. In
particular, small-scale ionospheric irregularities generated by different
physical processes may cause scattering effects on GNSS signals, producing
rapid fluctuations of the signal phase and amplitude as a result. Such
scintillations of GNSS signals are responsible for critical consequences
regarding applications, such as precise positioning, due to many resulting
effects: cycle slips, signal power fading, receiver loss of lock and poor
resulting satellite geometry.
Ionospheric Scintillation Monitoring Receivers collect high-rate GNSS
data. Specific scintillation parameters, such as the well-known S4 and Phi60
indices, are built on high-rate measurements performed on GNSS signals and
provide additional information to characterize the intensity of such an event
occurring at a specific geographic location at a given time. Spatial
Statistics belong to the field of Spatial Analysis, Geography and GIS
(Geographic Information System). This discipline allows to perform analyses
of data which are localised in space. Ionospheric Scintillation observations
achieved by ISMR stations can be characterized by a set of attributes (S4,
Phi60, Rate of TEC, etc.) including also the geographic location of their
respective Ionospheric Pierce Point (IPP). By combining the simultaneous
Multi-GNSS ISMR measurements from a network of ISMR stations, we can obtain a
spatially denser data set, able to support spatial statistics tests. The idea
of our research is to provide a spatio-temporal analysis of ionospheric
scintillation events over Equatorial regions by applying spatial statistics
on ISMR Multi-GNSS measurements. In particular, by using spatial statistics,
we aim to resolve specific issues regarding ionospheric scintillation data
from an ISMR network established in Brazil. The research consists in
spatially describing the data set, detecting and measuring potential spatial
autocorrelation, determining the scale of the spatial dependency and finally
producing an interpolated scintillation sky map at a given time. In terms of applicability of the
methodology, our research project consists in exploiting the spatio-temporal
analysis performed on ionospheric scintillation data in order to improve the
performances and the reliability of Absolute GNSS Positioning algorithms
under moderate ionospheric scintillation conditions. By assessing
correlations existing between specific ISMR data and classic GNSS
observations, the method could be extended to a more general usage which
would be independent of ISMR measurements. |
| 12:10 pm |
Space Weather and Ionosphere Investigations in the Frame
of LOFAR Program |
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Rothkaehl, H1; Krankowski, A2 |
| |
1Space
Research Center PAS; 2University of Warmia and Mazury in Olsztyn, Olsztyn, Poland |
| |
Polish astronomers and space
scientists are participating in the development and use of a radio
astronomical instrument of new generation: Low Frequency ARray - LOFAR,
exploring yet poorly studied range of low (<300 MHz) frequencies. It
constitutes a European array of thousands of antennas - a challenge for data
transfer and processing techniques. The LOFAR facilities in Poland will be
distributed among three sites: Łazy (East of Krakow), Borówiec near Poznan
and Bałdy near Olsztyn. All they will be connected via PIONIER dedicated
links to Poznan. Each site will host one LOFAR station (96 high-band+96
low-band antennas). They will most time work as a part of European network,
however, when less charged, they can operate as a national network. The active
Sun exercises a fundamental influence on the Earth's eco-space thereby
affecting the quality of life on Earth and the performance of technological
systems. The Sun releases sporadic
bursts of energy the most violent of which are identified as coronal mass
ejections (CME), clouds of highly ionized plasma ejected into interplanetary
space. Solar storms are known to have a damaging effect on critical
space-borne and ground-based technology systems and on the Earth’s ecosystem,
with immediate negative consequences for society. GPS and GALILEO can be
harmfully affected, electrical power distribution systems can break down due
to large geo-magnetically induced currents. Thus, a reliable space weather
forecast could mitigate the undesirable consequences of space weather,
especially its economic and social effects. The investigations with the help
of the LOFAR installation, besides monitoring the universe, will also be
oriented towards developing techniques to perform detailed diagnostics and
monitoring of the electromagnetic environment of the Earth, and for
proof-of-concept space weather applications, which is well in line with
ongoing efforts to coordinate and develop European space weather research
activities. |
| 1 |
Highlighted poster |
12:30 PM |
An Extended Short-term foF2
Forecast Model EUROMAP |
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|
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Mikhailov, A1; Perrone, L2; Shubin, V1 |
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|
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1IZMIRAN;
2INGV |
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|
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Earlier developed EUROMAP model
for short-term foF2 forecast over the European region has been extended by an
inclusion of ionospheric stations with historical observations for which
real-time foF2 observations are absent at present. Regression storm models to
describe strong negative foF2 disturbances have been created for such
stations and they participate in the foF2 mapping procedure during the
periods of strong geomagnetic disturbances. Similar to the basic EUROMAP
model the input driving parameters for such storm models are 3-hour ap
indices (converted to ap(t)) and effective ionospheric T-index. Under quiet
and moderately disturbed conditions with ap(t)£ 30 the dynamical foF2 IZMIRAN
model is used at these stations. In the case of strong negative disturbances
the EUROMAP model demonstrates on average a 25-40% improvement over the
IRI(STORM) model. The average improvement over climatology is 40-60%. In the
majority of cases this difference is statistically significant (³ 95%)
according to Student criterion. Examples of strong geomagnetic disturbances
with the main ionospheric trough occurrence at middle latitudes are given to
illustrate the possibilities of the developed model. |
| 2 |
Highlighted poster |
12:33 PM |
Ionosphere Threat Model
Assessment for GBAS at High Latitudes |
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|
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Lin, Y1; Jacobsen, K S1 |
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1Norwegian
Mapping Authority |
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|
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Undetected ionospheric plasma
gradients pose a serious threat to GBAS users. This threat is mitigated
through the use of a threat model, which quantifies the potential hazards
that may exist outside of the region that is visible to the GBAS system. The
parameters of the threat model are region-dependent, and have previously been
assessed for the CONUS (conterminous US) and central European regions. The Norwegian Mapping Authority (NMA)
routinely monitors ionosphere activity in high-latitude regions (55 - 80
degrees North). In this study, we analyzed the ionospheric plasma gradients
of several 2011 datasets with strong geomagnetic storms to determine
parameters for a high-latitude ionospheric threat model. These data were
obtained from a cluster of receivers in the vicinity of Tromsø (~ 70 degrees
North). By using the search in parameter space method, the main front
parameters (velocity, slope and width) were determined. We report that higher velocities are found
in the Norwegian region (up to 2000 m/s) in comparison with those measured in
the Germany and CONUS regions (< 1200 m/s). Most of the fronts are of
relatively small slope magnitude (< 60 mm/km), which is comparable with
those found in the Germany and CONUS regions. However, we note that the
dataset does not contain events as dramatic as e.g. the 2003 Halloween storms
in the US. |
| 3 |
Highlighted poster |
12:36 PM |
Potential of an Ionospheric
Disturbance Index to Estimate the Ionospheric Impact on GNSS |
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|
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Wilken, V1; Jakowski, N1; Berdermann, J1 |
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|
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1DLR |
| |
|
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Ionospheric perturbations can
have a strong influence on the use of global navigation satellite and other
space-based systems. The detection and estimation of spatial and temporal
variations of electron density in near real-time is difficult and subject to
current research. Based on former studies on the Disturbance Ionosphere Index
(DIX) here we present preliminary results concerning its capability to deduce
also directional information on horizontal structures of the ionospheric
electron density. Related results are derived from GNSS data sets obtained
over Europe during ionospheric storms. Although being limited due to the
regional data coverage the derived index indicates the potential of providing
valuable information on the actual performance of GNSS applications, e.g. the
achievable quality in positioning accuracy.
The index is designed to be reliable and robust and allows an easy and
objective interpretation. The calculation
of the ionospheric disturbance index is based on the Total Electron Content
(TEC) which has been confirmed in many publications to be an outstanding
parameter for quantifying the range error and the strength of ionospheric
perturbations. The quality of the index is dependent on the density of the
used GNSS data base. The analysis results shown are calculated using the IGS
and EUREF GNSS reference networks. DIX shall be made available to registered
users in near real-time via the Ionospheric Monitoring and Prediction Center
(IMPC) just established at DLR. |
| 4 |
Highlighted poster |
12:39 PM |
Effects of Solar Wind High-Speed
Streams on the High-Latitude Ionosphere: Superposed-Epoch Study |
| |
|
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Grandin, M1; Aikio, A2; Kozlovsky, A1; Ulich, T1; Raita, T1 |
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|
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1Sodankylä
Geophysical Observatory, University of Oulu; 2Departments of Physics, University of Oulu |
| |
|
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High-speed streams of solar wind
are the most important source of geomagnetic disturbances during a solar
cycle minimum. The ionosphere response to a high-speed stream impact,
especially at high latitudes, is not fully understood yet. We carried out a
statistical study of the effects of such perturbations on the high-latitude
ionosphere during the whole year 2006, using the superposed-epoch method for
data from the ionosonde of Sodankylä Geophysical Observatory (L=5.1). We found that the F layer critical
frequency drops typically by 0.4 MHz and the F layer virtual height increases
by about 30 km in 1 – 1.5 days after starting the solar wind speed increases.
We interpret these observations as a depletion of the F layer, which may be
due to enhanced plasma convection and increased chemical reaction rates in
the F region. Validity of such interpretation is supported by numerical
analysis of the continuity equation for ionospheric plasma. |
| 5 |
Highlighted poster |
12:42 PM |
The Ionosphere Irregularities
Modeling on the base of ROTI Mapping |
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|
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Cherniak, I1; Zakharenkova, I1; Krankowski, A1; Shagimuratov, I2 |
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|
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1GRL
UWM; 2WD
IZMIRAN |
| |
|
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The ionosphere plays an
important role in GNSS applications because it influences on the radio wave
propagation through out. The ionosphere delay is the biggest error source for
satellite navigation systems, but it can be directly measured and mitigated with
using dual frequency GNSS receivers. However GNSS signal fading due to
electron density gradients and irregularities in the ionosphere can decrease
the operational availability of navigation system. There were developed
several models in order to represent ionospheric fluctuations and
scintillation activity under different geophysical conditions, but they were
calibrated with data sets, that did not include GNSS derived data. It is very
actual to develop empirical model based on GNSS derived measurements which
can represent strong ionosphere fluctuation events. In this work we use the
data provided by the existing permanent GNSS network in order to make the
empirical model of ionospheric irregularities over the Northern hemisphere.
As initial data we used the daily dependences of the ROTI index as a function
of geomagnetic Local Time on the specific grid. The ROTI maps allow to
estimate the overall fluctuation activity and auroral oval evolutions. With
ROTI index maps it was determined the irregularities oval border and
averaging parameter – semi-hemisphere fluctuation index. It was investigated
the statistical and correlation dependences between Kp geomagnetic index and
parameters that characterized the ionosphere irregularities activity for period
of 2010 – 2014 years. The results of modeling and it validation for specific
events were presented. |
| 6 |
Highlighted poster |
12:45 PM |
New Space Weather Observation
Networks in Finland |
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|
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Ulich, T1; Raita, T1; McKay-Bukowski, D1; Vierinen, J2; Teppo, T1; Postila, M1 |
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1Sodankylä
Geophysical Observatory; 2MIT Haystack Observatory |
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|
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In 2013, the Sodankylä
Geophysical Observatory (SGO) was granted funds for renewing its space
weather instrumentation. SGO is therefore modernising and upgrading several
instrument networks in 2014 and 2015. The most important changes are
upgrading to 1-sec geomagnetic recording, renewing the Finnish Riometer
Chain, and the Finnish Satellite Tomography Chain. Riometers and tomography receivers are
implemented using software radio technology for maximum flexibility and
configurability. The tomography receivers are upgraded to receiver signals
not only from Cycada, but also other beacon satellites. The riometers will
continue as wide-beam riometers, but they are utilising LOFAR LBA antenna
technology and are multi-frequency systems, deployed as a meridional
chain. Furthermore, in an effort to
make data available via programmable interfaces, some of the SGO data
products are now fed into the MADRIGAL data base, and thereby into
ESPAS. Here we give an overview of the
instrumental changes and the services that are under development at SGO. |
| 7 |
Highlighted poster |
12:48 PM |
Computation of Ionospheric
Electric Potentials Using IRI-Plas |
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|
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Arikan, F1; Deviren, M N1; Cor, I1; Gulyaev, T2 |
| |
|
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1HACETTEPE
UNIVERSITY; 2IZMIRAN |
| |
|
|
Ionosphere is a part of the
upper atmosphere between 100 km and 1000 km altitude and consists of gases
ionized by solar radiation. The most important variable of Ionosphere’s
electric charges is electron density, N_e. N_e varies with respect to height,
location and time. It is not possible to determine exactly the value of the
electron density in a given time and position in the ionosphere. Therefore,
models have been developed to calculate the electron density. International
Reference Ionosphere Extended Plasmasphere (IRI-Plas) is the most widely used
physical model of climatic ionosphere.
Ionospheric electric potential is another variable that can be used to
examine the variability of ionosphere. For any location and time, the
electric potential is a function of charge distribution of the electron
density in given location. To calculate the quasi-static electric potential,
the most critical parameter is the dielectric constant. Dielectric constant
varies by plasma frequency, the collision of electrons with ions and neutral
molecules, frequency and the angle between propagation direction and magnetic
field vector. In this study, the dielectric constant is derived using the
refractive index. The refractive index is calculated from Appleton-Hartree
equation in a cold magnetoplasma where the cyclotron frequency of electrons
are employed as the operation frequency. The necessary parameters for
computation are obtained from the IRI-Plas with GPS-TEC and ionosonde foF2
and HmF2, NRLMSIS-00 and IGRF Geomagnetic Field models. The electric
potential is then calculated with Riemann sum of quasi-static volume
distribution of electric charge (N_e×e) with the computed dielectric
constant. It is shown that electric potential can be used as an indicator of
space weather variability. This study
is supported by the joint grant of TUBITAK 112E568 and RFBR 13-02-91370-CT_a. |
| 8 |
Highlighted poster |
12:51 PM |
In Situ Detections of Space
Weather by the LYRA Radiometer on Board the PROBA2 Satellite |
| |
|
|
Katsiyannis, T1; Dominique, M1; Ryan, D1 |
| |
|
|
1Royal
Observatory of Belgium/STCE |
| |
|
|
The Large Yield RAdiometer
(LYRA) is an ultraviolet irradiance radiometer on-board ESA's PROBA2
micro-satellite. Since it's launch in 2009 it observes the Sun in four
different passbands, chosen for their relevance to solar physics, aeronomy
and space weather. Flying on an altitude of 735km, LYRA proved to be an
excellent flare monitor and is involved in the analysis the atmospheric
composition of the Earth. One of the
most peculiar and intriguing results of LYRA is the detection of short,
strong, bursts that do not directly correlate with solar coronal events, nor
with pointing of the instrument to Earth's upper atmosphere, but correlate
well with high Kp index on Earth's surface. As LYRA has the ability to observe
in four different UV bandpasses, the comparison between the filters that
allow the detection of this activity versus those that do not, reveals very
interesting results as to the nature of those detections. This contribution will focus on the
investigation and identification of this phenomenon and it will include
crucial comparisons to other space-born instruments that do not detect the
same effect. |
| 9 |
Highlighted poster |
12:54 PM |
The EISCAT_3D radar system:
Conclusions from the Preparatory Phase |
| |
|
|
Tjulin, A1; Mann, I1; Heinselman, C1 |
| |
|
|
1EISCAT
Scientific Association |
| |
|
|
The EISCAT_3D radar system will
be a world-leading international research infrastructure located in the
Fenno-Scandinavian Arctic, using the incoherent scatter technique to study
geospace and to investigate how the Earth's atmosphere is coupled to space.
EISCAT_3D will consist of five phased array antenna sites located in
northernmost Norway, Sweden and Finland that, thanks to modern signal
processing and radar techniques, will be able to obtain observations with
significantly higher resolution than is possible with current radar systems.
In addition, EISCAT_3D will be constructed to manage continuous operation and
will be able to carry out simultaneous observations within a large volume of
the ionosphere above northern Scandinavia, making EISCAT_3D both a good
instrument for detailed studies of space weather impacts on the ionosphere as
well as for model verification. The EISCAT_3D radar system will be operated
by EISCAT Scientific Association and thus be an integral part of an
organisation that has successfully been running incoherent scatter radars for
more than thirty years. The EU FP7
funded Preparatory Phase, running 2010 - 2014, had the objective to ensure
that the EISCAT_3D project is sufficiently mature with respect to technical
development, organisation and finances for EISCAT_3D system to be realised.
The conclusions from the Preparatory Phase will be discussed, together with
the present status and future plans of the EISCAT_3D project. |
| 10 |
Highlighted poster |
12:57 PM |
Ionosphere Scintillation Mapping
using a Krigging Algorithm |
| |
|
|
Beniguel, Y1; Hamel, P1; Darces, M2; Wei, Y2; Hélier, M2 |
| |
|
|
1IEEA;
2University
Pierre et Marie Curie |
| |
|
|
This paper addresses the problem
of ionosphere scintillation mapping for now casting purposes. This problem is
of strong interest for many applications such as the satellite navigation,
the telecommunications and the space weather climatology. Ionosphere
scintillation characterizes the fluctuations on a signal after its
propagation through the random bubbles which might develop inside the
ionosphere. These bubbles may reach dimensions up to several hundreds of
kilometers. They are aligned with the terrestrial magnetic field and appear
after sunset, mostly at equatorial regions.
The scintillation mapping aims to give a planar view at the Ionosphere
Peak Point (IPP) altitude (usually set to 350 km) of the bubbles extent. At
low latitudes this corresponds to a cross section of these bubbles. A
climatological scintillation model such as GISM (Béniguel 2011) fails to
accurately produce ionosphere scintillation maps as the medium is described
in terms of statistical parameters which may depart from current
observations. Such a model might consequently over estimate or under estimate
the scintillation activity. The
algorithm presented in this paper is based on a Krigging technique. It uses
real or near real time data recorded by a network of 50 Hz receivers. These
data are supplemented on occasion by 1 Hz data provided by the IGS network.
The Kriging technique can be seen as a data assimilation technique. The
accuracy of the results is related to the accuracy and quantity of the
measurements. The more data it can be available at a given location, the more
accurate is the resulting map. The GISM model is used as a background tool to
fill the gaps between the measurements data points providing the algorithm
with the “variogram” function which plays a major role in this technique. |
| 11 |
Highlighted poster |
1:00 PM |
Scintillation Characterization
for SESAR 15.3.7 |
| |
|
|
Andalsvik, Y L |
| |
|
|
Norwegian Mapping Authority |
| |
|
|
Ionospheric disturbances can
cause serious disturbances to GNSS augmentation systems such as Ground Based
Augmentation Systems (GBAS). In addition to gradients scintillations are one
of the ionospheric phenomenons that can affect the signals. We present results from a study done for
SESAR 15.3.7 of scintillation characterization for high latitudes. The data
are obtained from Norwegian Mapping Authority’s scintillation receivers in
Norway mainly during the years 2012 and 2013. Results from receivers at
several relevant latitudes have been studied in the range between 65-79
degrees N. Approximately 16 periods of ionospheric activity were identified
and some of them were selected for more thorough studies. The main focus has
been on phase scintillation as amplitude scintillations are more commonly
associated with the equatorial region.
The characterization included scintillation per PRN, magnitude and
effect on different frequencies (here GPS L1 and GLONASS L2 CA). |
More Posters
The numbering on this page might differ from the numbering on the page with the short overview without abstracts.
| 12 |
|
The Annual Asymmetry in NmF2
During Deep Solar Minimum (2008-2009): December Anomaly |
| |
|
Mikhailov, A1; Perrone, L2 |
| |
|
1IZMIRAN;
2INGV |
| |
|
The annual asymmetry (the
December anomaly) in NmF2 variations has been known for more than 70 years
since the beginning of regular ionospheric observations. However until now
there is no either any more or less final morphological portrait or physical
mechanism of this phenomenon. The last deepest solar minimum in 2008-2009
when both solar and geomagnetic activity were at the minimum level opens an
unique opportunity to analyze the December effect and to specify the role of
the Sun-Earth distance. Using 6 conjugate mid-latitude ionospheric stations
the annual component in the NmF2 annual variations was shown to vary from 10
to 30% with the average value » 20%. The mean annual asymmetry in the
thermospheric parameters according to MSIS86, MSISE00 and JB2008 models was
shown to be sufficient to explain the observed annual asymmetry in daytime
mid-latitude NmF2 at least during the deep solar minimum. According to our
earlier proposed mechanism a 7% increase in the O2 dissociation rate due to
the decrease in the Sun-Earth distance in December–January compared to
June–July, an accumulation of atomic oxygen should take place in the
thermosphere in the vicinity of the December solstice resulting in » 20% NmF2
increase, which is close to the observed annual component in NmF2 variations
during daytime hours at middle latitudes. |
| 13 |
|
Dynamic and Thermal Processes in
Geospace during November 13 – 15, 2012 Magnetic Storm over Kharkov (Eastern
Ukraine) |
| |
|
Lyashenko, M |
| |
|
Institute of Ionosphere |
| |
|
Modeling results of the dynamic
and thermal process parameter variations in geospace plasma during November
13 – 15, 2012 magnetic storm over Kharkov are presented. For modeling were
used experimental data obtained on single in European mid-latitudes Kharkov
incoherent scatter radar. Calculations showed that during magnetic storm took
place increasing by modulus values of vertical component of transfer velocity
due to ambipolar diffusion up to 2.1, 1.9, 1.7 and 1.9 times at altitudes of
250, 300, 350 and 400 km respectively. The plasma flux density due to
diffusion increased up to 1.25 – 5.9 times in altitude range of 300 – 450 km.
During magnetic storm took place decreasing of the value of the energy input
to the electron gas about 34, 26, and 20% at the altitudes of 200, 250 and
300 km respectively. Calculations showed that heat flux density transferred
by electrons from plasmasphere to ionosphere in the main phase of the
magnetic storm increased up to 2 in the altitude range of 200 – 350 km.
Results of the zonal component electric field value estimates are presented.
During the November 13 – 15, 2012 magnetic storm the value of the electric
field zonal component was –9.5 mV/m. In quiet conditions, the value of the
electric field does not exceed units of mV/m.
The vertical component of plasma velocity due to electromagnetic drift
is calculated. For November 13 – 15, 2012 magnetic storm obtained that the
drift velocity reached its peak shortly after the beginning of the magnetic
storm and equaled 244 m/s. In this study the neutral wind velocity
calculation during November 13 – 15, 2012 magnetic storm over Kharkov also is
presented. Calculations showed that in quiet conditions values of the neutral
wind velocity ranges from –60 to –120 m/s. After the beginning of magnetic
storms and during the main phases occurred amplification directed to the
pole, the neutral wind. This behavior
of neutral wind velocity indicates that the effects of the magnetic storm
well manifested in the variations of the global thermospheric circulation
parameters. The simulation results
showed that the November 13 – 15, 2012 magnetic storm over Kharkov led to a
substantial restructuring of the dynamic and thermal regimes in the
ionospheric plasma. |
| 14 |
|
Ionospheric Outflows above
Quasi-Static Aurora: Discrete Arcs and Polar Cap Arcs |
| |
|
De Keyser, J1; Maggiolo, R1; Maes, L1; Gunell, H1 |
| |
|
1Belgian
Institute for Space Aeronomy |
| |
|
Some auroral phenomena have a
relatively long lifetime and evolve slowly. They appear to correspond to
quasi-static structures in the magnetosphere that are connected via a system
of field-aligned currents to horizontal ionospheric currents. In upward current
regions, magnetospheric electrons are accelerated downwards, resulting in
electron precipitation and subsequent heating of the ionosphere, while
ionospheric ions are accelerated upward, creating an outflow in which the
O+/H+ ratio exceeds typical magnetospheric values. We will review CLUSTER
observations of a regular quasi-static auroral arcs as well as
self-consistent electrostatic models of the corresponding auroral current
circuit, the particles, and the electric field. Another type of quasi-static
structures are polar cap arcs. These have been studied with CLUSTER as well.
We use a self-consistent model to describe the particles, the currents, and
the electric field configuration in both types of arcs. The model explains
the observed perpendicular electric potential variations and the parallel
potential differences reflected by the energies of the accelerated particles,
as observed by high-altitude spacecraft (above the auroral acceleration
region). In particular, we demonstrate how the ionospheric ions are
accelerated outward in both cases and discuss their signatures in the CLUSTER
measurements. Gaining insight in ionospheric outflows teaches us a lot about
the state of the topside ionosphere and about the composition in the
magnetosphere. These phenomena are spatially and temporally localized and
thus may produce local variations in the ionospheric electron content, which
may have space weather consequences on ionospheric radio signal propagation.
Auroral outflows should also be included in space weather models because of
their broader impact on the dynamics of the coupled magnetosphere-ionosphere
system since their relatively high O+ content modifies the magnetospheric
mass density. |
| 15 |
|
Prediction of the changes of
ionospheric characteristics during quiet magnetic conditions |
| |
|
Dziak-Jankowska, B1; Stanislawska, I1; Ernst, T2 |
| |
|
1Space
Reserch Centre PAS; 2Institute of Geophysics PAS |
| |
|
The prediction of ionospheric
drifts based on the changes of the vertical component of the external part of
the geomagnetic field will be
presented. The magnetic data are recorded in the Central Geophysical Observatory
of the Geophysical Institute in Belsk, 50 km from Warsaw. Magnetic data
recorded every 1 second and sent to
Warsaw every 5 minutes allow to
measure the changes of the geomagnetic field in real time. Quick procedures
filtrating data and extracting the external part of the geomagnetic data give
results within minutes after obtaining original data. During quiet magnetic
conditions the changes of the vertical component of the external part of
geomagnetic field exceeds the changes of the horizontal component. More than
70 percent of cases when the changes of vertical component exceeds the
changes of horizontal component correlate in time with the large deviations
from monthly medians of ionospheric characteristics: foE, foEs, h’F2. The
prediction of the changes of vertical component of the external part of the
geomagnetic field can be useful for prediction of the changes of ionospheric
behavior during quiet magnetic conditions. |
| 16 |
|
A Further Investigation Of The
Time Dependence On The Ionospheric Fof2 Variability During Magnetically Quiet
And Active Periods As Compared To The Relevant Results Of The Ariel 4
Satellite Ambient Electron Density At ~ 550 Km Altitude During The Declining |
| |
|
Tulunay, Y1; Timoçin, E2; Ünal, İ2 |
| |
|
1METU/ODTU Middle East
Technical University; 2İnönü Üniversitesi |
| |
|
E. Timoçin1, Y. Tulunay2, İ.
Ünal3 1İnönü Üniversitesi,
Fen-Edebiyat Fakültesi, Fizik Bölümü, 44280 Malatya, Turkey
2ODTU, Mühendislik
Fakültesi, Havacılık ve Uzay Mühendisliği Bölümü, 06800 Ankara, Turkey 3İnönü Üniversitesi, Eğitim Fakültesi, Fen
Bilgisi Öğretmenliği Bölümü, 44280 Malatya, Turkey ertim44@hotmail.com ytulunay@ae.metu.edu.tr
ibrahim.unal@inonu.edu.tr Potential
effects of the magnetically active periods on the mid–latitude ionosphere are
further investigated using ionospheric
critical frequencies from eight ionospheric stations for the 20st Solar Cycle
and seven stations for the 21st Solar Cycle. The ultimate goal is to seek if
the results exhibit any relevant signatures of the relevant results reported in the literature by employing the
ARIEL 4 satellite data (e.g. Tulunay et al. 2003; Tulunay et al.1996). In
particular, for a period of 42 days around each storm event excluding all
days with Ap≤ 9, a quiet standard diurnal variation was determined by day-by day averaging for
each hour UT by employing the Superposed
Epoch Analysis Technique (SPE). The regular diurnal, seasonal and solar cycle
variations were then removed from the data by subtracting from these the
“quiet” standard value. These obtained differences ΔfoF2 were sorted after
the storm event date. “The storm” criteria are fulfilled if Ap> 9. |
| 17 |
|
High Latitude Ionospheric
Monitoring by Incoherent Scatter Radar: Case Studies for Mitigation of Space
Weather Effects on Satellite Navigation |
| |
|
Enell, C-F1; Tjulin, A1; Häggström, I1 |
| |
|
1EISCAT
Scientific Association |
| |
|
Satellite navigation at high
latitudes suffers from disturbances caused by the structured and rapid
ionospheric electron density variations during geomagnetic substorms and
solar energetic particle events. The MISW FP7 project (MItigation of Space
Weather threats to GNSS services) is one among several projects that aims at
a better understanding of such effects and how to compensate for those. The total ionospheric electron content
determines radio signal delays and is inverted by receiving navigation
satellite signals at multiple frequencies. To improve the model of radio
propagation, independent measurements of ionospheric electron density
profiles will be provided by the EISCAT incoherent scatter radars on Svalbard
and the northern Fennoscandian mainland. These data will then be used to
calculate the actual ionospheric delays.
This study presents electron density profiles from the D region to the
topside ionosphere, analysed for several representative space weather cases
including days during the 1-year EISCAT radar run on Svalbard during IPY
2007-2008. |
| 18 |
|
The Discrimination between
Magnetospheric and Ionospheric Contributions in the Ground Manifestations of
Sudden Impulses. |
| |
|
Piersanti, M1; Villante, U1 |
| |
|
1University
of L'Aquila |
| |
|
The definite identification of
the characteristics of the geomagnetic response to SW pressure changes
represents an interesting element of the magnetospheric dynamics that is also
important in the Space Weather context. In the present analysis the aspects
of the global response from ground-based observations have been examined for
three case events, introducing a new approach that allows to discriminate
between magnetospheric and ionospheric contributions in ground Sudden Impulses manifestations. The separation
between the magnetospheric and ionospheric contributions is made by a
comparison between the observations at geostationary orbit and the
predictions of the Tsyganenko model for the different magnetospheric current
systems (from the magnetopause, ring current, tail current, etc.). The good
agreement between the geostationary observations at different positions and
the predicted field jumps, allows to subtract at each ground station the
expected DL field (of magnetospheric origin) from the experimental
measurements, in order to obtain a confident estimate of the residual DP
field (of ionospheric) origin at different latitudes and local times (LT).
The results of our analysis confirm that
the magnetopause current system is the key element during closed
magnetospheric conditions (Northward interplanetary magnetic field). The
inferred patterns of PI and the MI fields are consistent with those proposed
by Araki [1994]. |
| 19 |
|
Identification of the
Ionospheric Substorms with Global W-index Maps for 1999-2014 |
| |
|
Gulyaeva, T1; Arikan, F2 |
| |
|
1Institute
of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation; 2Department of EEE,
Hacettepe University, Beytepe, Ankara, Turkey |
| |
|
Ionospheric substorm is a fast
process when a substantial amount of energy of the solar wind and
magnetosphere enters into the auroral ionosphere. The bay in a record of
geomagnetic field horizontal component is observed in the Auroral Electrojet
(AE) or jet currents that flow at altitudes of the ionospheric E region in
the auroral zone. The AE index is measured in the Arctic auroral zone by
Kyoto World Data Center but there are no recordings for the Antarctic zone.
In this study, we identify the ionospheric storms and substorms in the Arctic
zone (magnetic latitudes greater or equal to 60 deg N) and Antarctic zone
(magnetic latitudes less or equal to 60 deg S) using the hourly ionospheric
weather global W-index maps. W-index maps are produced from JPL Global
Ionospheric Maps of Total Electron Content, GIM-TEC, for 1999-2014. It has
been observed that the storm and substorm W-index values manifest important
asymmetry between the two auroral zones. In particular, the occurrence of
positive storm and substorm events in both Arctic and Antarctic zones have
dominant annual waves with peaks near local winter that are smoothed out in
the global W storm. The peak of the negative storm and substorm occurrence
during equinoxes with dominant April value is twice as large in Antarctica as
compared with Arctic data. The results of this study indicate an urgent need
for monitoring of the Auroral Electrojet in Antarctica in addition to Arctic
service. Until this service is missing the W-index maps provide a unique
source of the ionospheric storms and substorms in the Antarctic zone. This
study is supported by the joint grant from TUBITAK 112E568 and RFBR
13-02-91370-CT_a. |
| 20 |
|
The Impact of Coronal Mass
Ejections on the Density of Ionosphere |
| |
|
Sheiner, O1; Vybornov, F1; Pershin, A1; Rakhlin, A1; Fridman, V1 |
| |
|
1Radiophysical
Research Institute |
| |
|
It is well known that coronal
mass ejections (CMEs) are one of the most important geoeffective solar
phenomena. At the same time, the nature of CMEs’ influence on the ionosphere
may be revealed using regular data of CMEs’ registration and temporal characteristics
of the ionospheric density. Consideration of the nature of geoeffective
manifestations of coronal mass ejections in the ionosphere is based on the
data of critical frequency of the reflection of radio signal during sounding
of ionosphere f0F2. First results were
based on the data of regular observations of critical frequency f0F2 during
periods of low and high solar activity (1975-1986) at the radioastrophysicall
observatory “Zimenki” (NIRFI, Nizhny Novgorod). The authors proposed the
procedure of the detection the influence of CMEs on the differential
parameters of the upper ionosphere f0F2 as more sensitive in comparison with
the traditional methods. This procedure was used in the present study of the
data of critical frequency f0F2, determined from uniform ionograms obtained
with the modern digital Ionosonde CADI. This ionosonde is installed at the
out-of-town observatory NIRFI “Vasilsursk” (near Nizhny Novgorod), and
working program of regular observations allowed to obtain ionograms at least
once in 1 minutes, the accuracy of determining the critical frequency was
less than 50 kHz. The characteristic
time of the initial CME’ impact on ionosphere was a few tens of minutes,
that, can be assumed, is determined by a direct effect of X-ray emission
produced during the CME’ formation and onset from the solar disk on the
ionospheric plasma. Characteristic time interval of general phenomenon of
CME’ impact on the ionosphere, is a few days. This characteristic time,
determined from the behavior of f0F2 deviations, coincides with the time of
existence of the perturbation generated by ICMEs in the near-Earth space. |
| 21 |
|
Large-Scale Ionospheric
Disturbances at the Recovery Phase of Moderate Geomagnetic Storm of October
2008 |
| |
|
Zakharenkova, I1; Astafyeva, E1 |
| |
|
1Institut
de Physique du Globe de Paris |
| |
|
It is known that strong
geomagnetic disturbances may provoke sufficiently large effects in the upper
atmosphere and ionosphere, degrading the performance of satellite-based
communications. However, besides intense geomagnetic storms and super-storms,
special attention should be focused on the study of the geomagnetic storms
occurred during low solar activity, e.g. the extended solar minimum of 23/24
solar cycles, when ionosphere was rather poor in density and reacted
sensitively to the very moderate geomagnetic disturbances. In this work, we
use the multi-instrumental database of the ground-based and satellite-born
observational facilities to study the global redistribution of the
ionospheric plasma during moderate storm of 11 October 2008. We involved into
analysis multi-site network of the ground-based stations of the ionospheric
vertical sounding, permanent network of GPS ground-based receivers (IGS),
several Low Earth Orbit (LEO) satellite missions – CHAMP, FORMOSAT-3/COSMIC
and altimeters Jason-1 and Jason-2. Well-pronounced positive effect was
observed in African and American sectors during daytime. CHAMP in-situ
measurements of plasma density at altitude of about 350 km, as well as the
topside TEC, derived from CHAMP onboard GPS precise orbit determination (POD)
antenna, indicate the certain redistribution of the ionospheric plasma
density at the recovery phase of geomagnetic storm. For African sector the
decrease of the Equatorial Ionization Anomaly (EIA) manifestation and
considerable displacement of the ionospheric plasma toward the higher
latitudes (up to 60 MLAT) were observed. The strong increase of GPS TEC, POD
TEC and in-situ plasma density over European/African mid-latitude regions has
rather short duration and was observed within 11-15 UT. For the American
sector, the electron density enhancement was mainly related to the
intensification of the EIA with increase of the electron density at both EIA
crests and further displacement of the EIA crests from the magnetic equator
towards mid-latitudes. The most pronounced ionospheric effects were observed
at low latitudes of Northern America during 17-22 UT, at the recovery phase
of the storm. Main peculiarities of the observed ionospheric plasma density
redistribution and physical mechanisms are discussed in the paper. |
| 22 |
|
Probing the Ionosphere with
Broadband Low-Frequency Observations of Ionospheric Scintillation |
| |
|
Fallows, R1; Coles, W2; Forte, B3 |
| |
|
1ASTRON;
2UCSD; 3University of Bath |
| |
|
Observations of strong natural
radio sources such as Cassiopeia A over the frequency range 10-250 MHz using
both the Kilpisjarvi Atmospheric Imaging Receiver Array (KAIRA) in arctic
Finland and the Low Frequency Array (LOFAR) centered on the Netherlands show
almost continual ionospheric scintillation. Dynamic spectra of these
observations show a clear progression in frequency of the scintillation going
from weak to strong scattering. The effects of refraction due to large-scale
structure in the ionosphere are also visible at the lowest frequencies.
Secondary spectra (the two-dimensional power spectrum of a dynamic spectrum)
of short segments of these data sometimes show an arc structure: These
"scintillation arcs" have been found in observations of
interstellar scintillation for a number of years, where they have proved a
useful tool for modeling parameters such as the distance to the scattering
“screen” and the velocity of the scattering medium transverse to the line of
sight. However, these two parameters are inherently linked in modelling which
means that one needs to be known before the other can be established
accurately. The dense core of the
LOFAR array has been used to take temporal cross-correlations between station
pairs to establish a picture of the velocity field in the ionosphere; with
KAIRA other supporting instrumentation can be used to estimate ionospheric
velocities in nearby regions. These
velocities are used to attempt to establish the altitudes dominanting
scattering in the ionosphere. |
| 23 |
|
Study of Amplitude and Phase
Perturbations on VLF Signals Induced by Solar Flares in the Region of the
Morning and Evening Terminator |
| |
|
Sreckovic, V1; Sulic, D1 |
| |
|
1Institute
of Physics |
| |
|
The sensitivity of very low
frequency (VLF, 3 - 30 kHz) propagation in the lower ionosphere makes it an
ideal probe for remotely sensing the ambient state and localized
perturbations of the ionosphere. The focus of this work is on the extraction
of D-region electron density (in the range of ~ 60 – 90 km) from VLF signal
perturbations induced by solar X-ray flares. The perturbations in the
D-region induced by solar flares were studied using recorded amplitude and
phase data from VLF transmitters, in period July 2008 – May 2014. All data
were recorded by AWESOME system at Belgrade station (44.850 N, 20.380 E). One
of the best defined signals received at Belgrade station originates at the
NSC transmitter from Sicily Italy at 45.90 kHz. Other signals received at
Belgrade station include: DHO (Germany
23.4 kHz), GQD (UK 22.21 kHz) and ICV (Italy 20.27 kHz). Great circle
distances for those signals are in the range from 952 km to 2000 km. All VLF
radio signals propagate from west to east. In this study we considered
amplitude and phase perturbations on VLF radio signals induced by solar X-ray
flares in the region of the morning and evening terminator. There are
differences between morning and evening terminator in lateral gradients of
electron densities in the ionosphere. We expected and estimated differences
in perturbations of amplitude and phase on NSC/45.90 kHz radio signal induced
by solar X-ray flare occurred in hours close after sunrise and before sunset.
The observations include solar X-ray flares with magnitudes in the range from
C2 (IX = 2•10-6 Wm-2 at 0.1 – 0.8 nm) to X1.44 (IX = 1.44•10-4 Wm-2). On the
22nd April 2011 M1.2 class solar X-ray flare started at 15:43 UT with peak at
15: 53 UT (IX = 1.2•10-5 Wm-2) only few minutes later than the time of
amplitude minima on NSC/ 45.90 kHz radio signal. Instead to follow decreasing
amplitude suddenly jumped which gave amplitude enhancement up to 11 dB.
Simultaneously phase had enhancement of about 700 As the intensive X-ray
radiation from the solar flare impact the lower ionosphere it causes
exceptionally high levels of ionization. The result is the significant
increase in amplitude of the received signal and a phase advance which means
a shorter overall path length. |
| 24 |
|
Ionospheric Modelling at IPS |
| |
|
Francis, M1; Terkildsen, M1; Bouya, Z1 |
| |
|
1IPS
Radio and Space Services, Australian Bureau of Meteorology |
| |
|
The Ionospheric Prediction
Service (IPS) within the Australian Bureau of Meteorology rovides a range of
ionospheric prediction, warning and alert services covering HF
communications, GNSS and satellite communications. This presentation will
detail our current research and development directions. We are developing a short term (<24
hours ahead) forecast model for the Australian region TEC, based on the near
real time TEC map we currently produce. The approach under investigation uses
a PCA decomposition of recent observered maps to reduce the dimensionality of
the TEC map by mapping it to its eigen-space and keeping to few most
significant eigen-vectors. An artificial neural network is then used to
predict the future eigenvalues taking into account geomagnetic activity. An ionospheric gradient index for
quantifying the degree of ionospheric activity in terms of spatial and
temporal ionospheric gradients is being developed. This index, based on raw
GNSS data, and the associated alert service is pertinent to applications
dependent on precise GNSS positioning navigation and timing that are impacted
by the presence of steep ionospheric gradients and/or rapid variations in ionospheric
delay. IPS HF services, which advise
users on useable frequency ranges over given communication paths, are
parametrised via a single index known simply as T. We are developing more
accurate automated T index forecasts over the 1-3 day period that is
currently forecast largely via a human forecaster as well as longer term
forecasts up to 90 days ahead. |
| 25 |
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Features of the Modern
Diagnostic Methods of Ionospheric Turbulence |
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Vybornov, F1; Pershin, A1; Rakhlin, A1; Sheiner, O1 |
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1Radiophysical
Research Institute |
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It is known that rapid
fluctuations of the amplitude and phase in the signal received from the signal transmitters on the board of
satellites, can occur due they pass through the ionosphere with small-scale
inhomogeneous structure of ionospheric
plasma. Earlier we have shown that the
study of the multifractal structure of the fluctuation of amplitude or phase
of the signal received from the Earth satellites allow you to define the
parameters of the multifractal structure of ionospheric turbulence. In the
present paper we considered the question about practical application of
various research methods self-similar structure of the ionospheric
turbulence: the spectral correlation method, the multidimensional structure
functions method, the wavelet transform method (WT), the method of
multifractal-detrended fluctuation analysis (MF-DFA). Also we study the
applicability of the method of maxima of wavelet transform modulus (WTMM )
for remote sensing of small-scale ionospheric turbulence . The first time
presented the results of processing of transionospheric signals at a
frequency 150 MHz obtained by the method of
analysis the non-stationary signals - MF-DFA. The values of scaling
exponent obtained by this method were
close to the values obtained by the MSF method. Also shows the results of processing of the
transionospheric signals using
different wavelets. Here is presented a comparative analysis of the methods
WT and WTMM for diagnostic of ionospheric turbulence. It is shown that in
studies of the fractal properties of the ionospheric turbulence use a simple
method of wavelet transform may have certain advantages over the method of
modulus maxima of wavelet transform, as the results of the WT are taken from
the entire range of signal processing and characterize the entire data set on
this interval. |
| 26 |
|
Halloween Storm 2004 impact on
Ionospheric Drifts |
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Kouba, D |
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IAP CAS |
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|
The present paper shows effect
of an extreme geomagnetic storm (November 2004) on ionospheric drifts
measured using the Digisonde network. Currently, drift measurements are a
standard part of ionospheric sounding at most Digisonde stations. However,
during the studied storm in November 2004 drift measurements were only
realized at several Digisondes. The
paper shows results of comparison of drift data from storm time and data
obtained under quiet conditions. The drift data show clear signs that the
ionosphere was strongly influenced duringthe geomagnetic storm. Time
evolution of drift data from the Pruhonice station during the storm can be
divided into three or four phases.
Initial phase of the storm is characterized by increase of values of
both vertical and horizontal components, and rapid changes in velocity vector
(both magnitude and direction). Following phase is characterized by a gradual
transition of the vertical component of the velocity from a large negative
values to a large positive. Positive values of the vertical component are accompanied by
large positive values of westward component. This phase was observed three
times during the studied storm and its duration gradually decreased. Whole phase
can be interpreted as a downward deflection and subsequent leakage of
plasma up to the Westward. Drift
data measured during the storm at the Pruhonice observatory are compared with
data from other Digisondes for which Halloween storm drift data are available. |
| 27 |
|
Latitudinal and Longitudinal
Differences in Ionospheric Response to Magnetic Disturbances |
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|
Buresova, D1; Lastovicka, J1; Kouba, D1; Urbar, J1; Novotna, D1 |
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1Institute
of Atmospheric Physics of the Academy of Sciences of the Czech Republic |
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|
Investigations of differences in
ionospheric response to geomagnetic disturbances are based on data of
selected ionospheric sounding stations located at different magnetic
longitudes of the Northern and Southern Hemispheres. The variability of main
ionospheric parameters, critical frequency foF2 and its height hmF2, obtained
for different longitudinal sectors of both hemispheres for initial, main and
recovery phases of magnetic storms of different intensity, is analyzed over
the last two solar cycles (22 and 23).
Specific peculiarities in the ionospheric response to geomagnetic
disturbances appear during the past extreme solar cycle minimum (2007-2009). |
| 28 |
|
The Variability of Effects of
the CIR and HSS Events on the Ionospheric Disturbed Periods Including Storm
Recovery Phase |
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|
Urbar, J1; Buresova, D1; Lastovicka, J1; Mosna, Z1 |
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1Institute
of Atmospheric Physics AS CR |
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|
Relevant studies describe the
propagation of the solar wind disturbances into the outer magnetosphere and
model their influence on the local plasma properties. The understanding of
the coupling processes between the magnetosphere and ionosphere has also reached
the capability of predictions, nevertheless the developed models still need
calibrations by the empirical observations. Numerous multi‐instrumental case
studies and large‐scale statistics of ionospheric response to specific solar
wind precursor events are vital for the development in the field. The entire
recovery phases following the storm culminations need to be included and
addressed specifically. However, even within the storm recovery phase, there
are characteristic anomalies during the gradual return to the normal state of
the ionosphere, which is often very prolonged. This contribution provides the
case and statistical analysis of the variability of effects of CIR and HSS
events on the ionospheric disturbed times including storm recovery phase
during the last solar minimum. For the CIR and HSS events, the ionosphere
remains affected by Alfven wave driven changes in IMF and fast solar wind.
The observed effects at the middle latitudes on both hemispheres are
discussed. |
| 29 |
|
Validation of the Cyprus
Ionospheric Forecasting Service during Disturbed Geomagnetic Conditions |
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|
Economou, L1; Haralambous, H2; Pezzopane, M3; Zolesi, B3; Pietrella, M3; Cander, Lj R4 |
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|
1University
of Nicosia Foundation (UNRF); 2Frederick Research Center; 3Istituto Nazionale di Geofisica e Vulcanologia; 4STFC Rutherford Appleton
Laboratory |
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|
The CIFS (Cyprus Ionospheric
Forecasting Service) is a High Frequency (HF) operational service for
real-time specification (now-casting), short-term forecasting and long-term
prediction of the state of the ionosphere over the eastern Mediterranean
region. This real-time service is based on the Simplified Ionospheric
Regional Model (SIRM) as a background to assimilate in real time the critical
frequency of the F2 layer (foF2) and the propagation factor (M(3000)F2)
values provided by digisonde measurements from Nicosia (Cyprus). This paper
presents a validation study of the now-casting generated maps of foF2 within
the eastern Mediterranean area from 20° E to 45° E in longitude and 30° N to
40° N in latitude using foF2 values from the Athens digisonde during periods
of disturbed ionospheric conditions. |
| 30 |
|
IRI STORM validation over Europe |
| |
|
Haralambous, H1; Vryonides, P1; Leontiou, T1; Oikonomou, C2; Dobrica, V3; Demetrescu, C3; Ionescu, D3; Maris, G3 |
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|
1Frederick
Research Center; 2FRC, Frederick Research Center; 3Institute of Geodynamics of the Romanian Academy, Bucharest,
Romania |
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|
The International Reference
Ionosphere (IRI) model includes an empirical Storm-Time Ionospheric
Correction Model (STORM) extension to account for storm-time changes of the F
layer peak electron density (NmF2) during increased geomagnetic activity.
This model extension is driven by past history values of the geomagnetic
index ap (The magnetic index applied is the integral of ap over the previous
33 hours with a weighting function deduced from physically based modeling)
and it adjusts the quiet-time F layer peak electron density (NmF2) to account
for storm-time changes in the ionosphere. In this investigation manually
scaled hourly values of NmF2 measured
during the main and recovery phases of selected storms for the maximum solar
activity period of the current solar cycle are compared with the predicted
IRI-2012 NmF2 over European ionospheric stations using the STORM model
option. Based on the comparison a subsequent performance evaluation of the
STORM option during this period is quantified. |
| 31 |
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Iono-tropospheric Disturbances
Mitigation System for SSA Purposes |
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|
Stanislawska, Iwona1; Tomasik, Lukasz1; Pozoga, Mariusz1; Swiatek, Anna1; Dziak-Jankowska, Beata1 |
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1Space
Research Centre PAS |
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Space Situation Awareness
Concept in the layer related to space environment is based on monitoring and
characterizing of environmental conditions relevant to space system and
mission effects. SSA to be efficient needs access to actual and forecast
terrestrial, near-space and space environmental information to predict,
respond to and exploit environmental effects to operational activity in
space. Ground-based space systems like
surveillance tracking radars for space control can be affected by the
environment. Satellite system communication links and the satellite’s
respective ground sites can be affected by the environmental conditions in
which they operate as well Thus, the tools to implement the environmental information
to improve performance or protect the systems is needed for effective
SSA. One of the most important
environmental components which set up the space weather element influenced on
efficiency of communication channels and surveillance tracking radars is the
ionosphere, exactly its density gradients and small-scale irregular
structure. The resulting properties like ionospheric refraction and signal
scintillation cause the spectrum of effects.
Generally, the quality of signal propagating through the atmosphere
and ionosphere in different parts of spectrum, depends, from one side, on the
atmospheric ingredients like dry air, water vapor, hydrometeors, and other
particulates (sand, dust, aerosols, and volcanic ash) , on the other side on
ionospheric plasma structures introduce microwave propagation delays. These
delay, must be properly characterized to achieve the highest accuracy in
space related applications. Thus, it is clear that the knowledge of large
scale and small scale distribution of electron density in the ionosphere is
one of the important task for operational SSA. The method of solution
generally has to model an anisotropic thermosphere using a mapping function
and consider horizontal plasma gradients. More complex models would require a
more sophisticated approach to resolve additional irregular ionospheric
parameters. Special cases have to deal with complex modeling assimilated by
independent measurement of thermosphere anisotropies. For these purposes the
following tasks have been elaborated:
Elaboration for some existing dural ionospheric model of electron
density (like NeQuick , PLES ) tools for regional assimilation of their
profiles. Determination the
model of small scale structures “on the profile” with appropriate dielectric
tensor for different type of plasma and ingredients. Integrate the small scale and large scale
ionospheric profile of ionospheric density
Incorporate the “ray-tracing”
tool into SSA propagation package
Formulate the Service suitable for SWENT structure We present here the modeling of
environmental conditions for SSA purpose including Space Weather elements
that are integrated into two other layers as well as located in the European
architecture of SSA Structure. |
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