Plenary - Solar Flare Prediction: Progress and Challenges
Manolis K. Georgoulis - D. Shaun Bloomfield - Peter T. Gallagher
Thursday 21/11, 09:00 - 10:30 and 11:00 - 12:30
Forecasting of sun-induced space weather includes three major challenges: prediction of solar flares, prediction of
coronal-mass-ejection (CME) arrival and geoeffectiveness, and prediction of the arrival of (flare- or CME-accelerated)
solar energetic particles. A distinct peculiarity about flare forecasting is that there is obviously no early warning for
flare photons, leaving also a very slim early-warning window for possible flare-related SEPs. As a result, major solar flares
with a space-weather interest should ideally be predicted before they occur.
This ambitious goal has, in recent years, led to
a wide variety of flare-prediction methods and classes of methods. This session aims to browse through the arsenal of
techniques and critically review, discuss, and highlight their most innovative aspects. The session’s objective is to
clearly outline the current state-of-the art and to identify and promote possible research avenues that may lead to future
breakthroughs. While flare prediction will form the core of this session, presentations about CME- and SEP-prediction will
also be accommodated in the understanding that they promote the connection of these phenomena to flares.
Oral contributions
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Title
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09:00
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Invited
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Solar Flare Forecasting: a "State of the Field" Critical Review.
Leka, K.D.
NorthWest Research Associates, UNITED STATES
It can be argued that the most stringent test of understanding a system,
is to be able to use available observables to forecast a future outcome.
It can also be argued that solar flares may not be deterministic, and
even if they are, our present understanding is nowhere close to being
able to predict the time, location, magnitude and space weather impact
of a solar flare with any certainty. Still, solar flare prediction is
a needed component of our international space weather infrastructure.
Many research groups around the world are investigating ways to
improve flare forecasting methods, especially in light of new observational
data available. I present a brief report of the "state of the field",
summarizing insights gained from recent workshops (held in 2009 and
2013) aimed at head-to-head comparisons of flare forecasting methods in
specific contexts. In summary, today's methods combine sophisticated data
analysis with statistical or machine-learning algorithms which generally
result in probabilistic forecasts. While the question of whether any
of the presently developed methods clearly outperforms the others is
still under investigation, the problem of how to answer that question presents
interesting challenges for study design, data handling, statistical
verification algorithm development (and psychology). I describe the
standard skill scores being applied to the careful comparisons and some
of the preliminary results, including what appear to be common successes
and continued challenges among today's methods.
(Funding for the workshops and subsequent analysis was made possible by
NASA/Living with a Star contract NNH09CE72C and NASA/Guest Investigator
contract NNH12CG10C.)
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2 |
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09:30
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How can Subsurface Flow Properties Contribute to more Accurate Solar Flare Predictions?
Reinard, Alysha1; Komm, Rudolf2; Hill, Frank2
1NOAA/SWPC, UNITED STATES;
2National Solar Observatory, UNITED STATES
Subsurface flows beneath active regions provide information
about the processes that occur prior to and during flares. We have
shown (Reinard et al. 2010) that subsurface flows exhibit measurable
changes prior to flare occurrence. However, this relationship is not
yet reliable on a case-by-case basis. We present recent research
designed to improve the correlation between subsurface flow properties
and solar flaring. We use measurements derived from GONG data using the
ring-diagram technique, which provides flow properties between 0-16Mm
below the solar surface. Our investigations include the effects of
CME-association, hemispheric origin, and nearby active regions.
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3 |
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09:45
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On Fractal and Multifractal Parameters as Flare Precursors
Ermolli, Ilaria1; Giorgi, Fabrizio2; Romano, Paolo3; Zuccarello, Francesca4
1INAF, ITALY;
2INAF - Osservatorio Astronomico di Roma, ITALY;
3INAF - Osservatorio Astrofisico di Catania, ITALY;
4Universita' degli Studi di Catania, ITALY
Several studies show that fractal and multifractal parameters
derived from photospheric magnetic field measurements may help assess
the eruptive potential of Active Regions (AR). However, the results
derived from a recent analysis seem to discard all previously collected
evidences, by showing that none of the widely-used indicators analyzed
in the study allows to distinguish AR with major flares from
flare-quiet ones, though both regions exhibit significant fractality
and multifractality. In this framework, we explore whether
higher-resolution, higher-cadence, and higher-sensitivity data than
those employed in previous analyses might help to clarify the reason of
conflicting results presented in the literature. To this aim, we
analyzed two datasets of photospheric magnetograms of a flaring and a
flare-quiet ARs, NOAA 1158 and NOAA 1117 respectively, which were
observed simultaneously with SOHO/MDI and SDO/HMI. The latter
observations are characterized by a higher spatial and temporal
resolution than the SOHO/MDI data, which are analysed for comparison
here and were widely employed in previous studies. Besides, we analyze
a larger sample of ARs observed with SDO/HMI and associated with M- and
X classes flare events. The results obtained are discussed with respect
to those published in the literature.
This study has been carried out in the framework of
the EU FP7 project "eHEROES - Environment for Human Exploration and
RObotic Experimentation in Space" (grant n. 284461).
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4 |
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10:00
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Pre-Flare Dynamics of Sunspot Groups
Ludmány, András; Korsós, Marianna
Konkoly Observatory, HUNGARY
The most probable sites of flare onset are the regions of high
horizontal magnetic field gradient in solar active regions. Besides the
localization of flare producing areas the aim of the present work is to
reveal the characteristic temporal variations in these regions prior to
flares in order to improve the forecast capability. The method uses
sunspot data instead of magnetograms and follows the behaviour of a
suitably defined proxy measure representing the horizontal magnetic
field gradient. The empirical basis of the analysis is the SDD
(SOHO/MDI-Debrecen Data) sunspot catalogue. The following pre-flare
signatures seem to be diagnostically useful predicting tools in the
variation of the magnetc field gradient: i) steep increase, ii) high
maximum, iii) significant fluctuation and iv) a gradual decrease
between the maximum and the flare onset. The achived maximum has a
linear relationship with the intensity of the flare. After the maximum
the gradual decrease of the gradient has a characteristic time of about
10 hours. Close tracking of the variations of the magnetic field
gradient allows to esteem the intensity of the flare and the expected
time of the flare onset.
The research leading to these results has received
funding from the European Community's Seventh Framework Programme
(FP7/2012-2015) under grant agreement No. 284461.
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5 |
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10:15
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Does Quantifying the Evolution of the Photospheric Magnetic Field Lead to Improved Solar Flare Prediction?
Barnes, Graham; Leka, K.D.
NWRA, UNITED STATES
Knowledge of the state of the photospheric magnetic field at a
single instant in time does not appear sufficient to completely predict
solar flares, although it may provide necessary conditions, such as the
free magnetic energy needed for a flare to occur. Given the necessary
conditions, evolution of the field, possibly by only a small amount,
may trigger the onset of a flare. We present the results of a study
using time series of photospheric vector field data from the
Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamics
Observatory (SDO) to quantitatively parameterize both the state and
evolution of active regions - their complexity, magnetic topology and
energy - as related to solar flare events. Statistical tests based on
linear and nonparametric Discriminant Analysis were used to compare
pre-flare epochs to a control group of flare-quiet active regions. The
improvements in forecasts that include evolution of the field, as
quantified by standard skill scores, will be presented.
Funding for this work was provided by NASA/Guest Investigator contract NNH12CG10C.
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6 |
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11:00
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Invited
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Exploiting Solar Flare Statistics for Flare Prediction
Wheatland, Mike
The University of Sydney, AUSTRALIA
The solar flare mechanism remains incompletely understood, and existing
methods of flare prediction are probabilistic, rather than
deterministic, relying on imperfect indicators of flare likelihood.
The existing methods of prediction are briefly reviewed, and then an
approach to the problem, relying only on the past time series of
flare occurrence (Wheatland 2004; 2005), is revisited. A specific
improvement to the method is presented: an implementation of a new
optimal Bayesian change-point algorithm (Scargle et al. 2013) to
determine the current rate of occurrence of small flares.
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7 |
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11:30
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Chromospheric Magnetic Field of Exploding Solar Active Regions
Choudhary, Debi Prasad
California State University Northridge, UNITED STATES
How changes in the three-dimensional magnetic field of solar
active region are related to Coronal Mass Ejections (CME) is an
important question for contemporary solar physics. Complex active
regions are the predominant source of powerful high-speed CMEs, which
can result in strong geomagnetic storms. In this paper we present the
properties of chromospheric magnetic field of active regions that
produced solar flares and CMEs using observations of the Synoptic
Optical Long-term Investigations of the Sun (SOLIS) facility operated
by the National Solar Observatory. Currently, the SOLIS Vector
Spectromagnetograph (VSM) is the only instrument that is capable of
obtaining full Stokes profiles in both the photospheric Fe I ë630.2 nm and chromospheric Ca II ë854.2
nm lines on a daily basis. VSM also has the capability of making rapid
scans covering an area sufficiently large to contain an active region.
We shall present the Stokes profile characteristics of photospheric and
chromospheric lines of few CME source regions.
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8 |
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11:45
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The Role of Magnetic Reconnection in Flares and CME Energetics: Lessons Learned from Analytical Theory
Seaton, Daniel1; Forbes, Terry2; Reeves, Katharine3
1Royal Observatory of Belgium, BELGIUM;
2University of New Hampshire, UNITED STATES;
3Harvard-Smithsonian Center for Astrophysics, UNITED STATES
It is widely accepted that magnetic reconnection is the
primary mechanism for energy release during solar eruptions. However,
the question of how, exactly reconnection works in the solar corona
remains very much under discussion. In fact, we can learn much about
how reconnection drives flares and CMEs from relatively simple,
analytical models. Here we discuss some recent analytical results and
the relevance of these results for flare and CME forecasts. In
particular we will discuss how the reconnection rate and location, and
therefore the rate and locations of energy release, can be influenced
by the local conditions and asymmetric magnetic fields in the corona at
the time of an eruption. We highlight some lessons that can be gleaned
from analytical theory for real-time space weather forecasters and
model developers.
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9 |
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12:00
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Perturbation of Nuclear Decay Rates During Solar Activity: A Method of Solar Storm Prediction
Mohsinally, Tasneem1; Jenkins, Jere2; Fancher, Sean1; Fischbach, Ephraim1
1Purdue University, UNITED STATES;
2Texas A&M, Purdue University, UNITED STATES
Introduction
A possible basis for an early warning system for solar
flare activity was observed by happenstance during otherwise routine
measurements of Mn-54 decay gammas with an ordinary scintillation
detector [Astropart. Phys. 31, 407 (2009)]. Further investigation by
our group led to additional evidence pointing to a possible solar
influence on terrestrial nuclear decay rates [Astropart. Phys. 32, 42
(2009), Space Sci. Rev. 145, 285 (2009)]. The only known particles
emitted by the Sun which could have caused the observed phenomena are
neutrinos, particularly in light of the fact that whatever agent is
causing the decay rate changes experienced unimpeded passage through
the Earth and the Sun. As noted in [Astropart. Phys. 31, 407 (2009)],
the observed decrease in the Mn-54 decay rate began to occur up to 36
hours prior to the flares, thus providing a possible predictive method,
which could offer stakeholders the ability to protect vulnerable assets
and systems.
Background
A significant body of work has been published to date
detailing the observations of this putative solar influence beyond the
flare-associated decay rate changes. Annual and sub-annual
periodicities (~2/yr and 10-12/yr) have
also been observed, and these are difficult to attribute to possible
known environmental influences. Moreover, the number of
observations--by independent groups--of similar periodicities, across a
number of different isotopes and diverse detector types [see Table 1 in
Appl. Radiat. and Isotop. 74, 50 (2013)], essentially eliminate all
known environmental influences as the cause. Although there is no
physical mechanism presently to explain these effects, particularly in
light of the extremely low cross-section for known neutrino
interactions, it is likely that these effects arise from some new
phenomenon.
The work done by our group in November and December of
2006, at the end of solar cycle 23, exhibited decay rate changes
associated with several flares during the time period. This prompted
further investigations of the literature, and analyses of nuclear decay
data generously offered by other groups at different institutions
world-wide. These analyses led to the identification of the
aforementioned periodicities, or non-random behavior, in what should be
randomly distributed data [Astropart. Phys. 34, 121 (2010), Solar Phys.
267, 251 (2010), Solar Phys. 272, 1 (2011)].
Method Development
Additional measurements of Mn-54 decays to search for
have been underway for the last five years, and recent results are
promising. While is it certain that this methodology does not show the
same effects for all solar flares, decay rate changes associated with a
reasonable percentage of C, M and X class flares can be identified.
Analytical methods are being developed that may provide real-time
predictive capability for major flares with the ability to attach
confidence levels to the flare prediction. Additional detector systems
are being installed to increase data flow and offer a better
statistical basis for observed flare correlations. As we are nearing
the peak of Solar Cycle 24, we have an excellent opportunity for
observations and development of the algorithms that will be used.
System Development
Several years of data on Mn-54 decays, taken at 1-hour
intervals, are currently available from sites at Purdue University
(Indiana, USA) and at the United States Air Force Academy (Colorado,
USA). In addition, a third site in Santiago, Chile, has recently been
established. Our goal is to establish a world-wide network of similar
installations, acquiring data synchronously, and transmitting these
data to one or more central servers. Software is currently under
development which would allow these data to be combined and analyzed in
real-time to search for common features, which would signal an imminent
solar storm. Since the statistical power of such an array would
increase as N1/2 for N sites, an order of magnitude improvement could be realized by an appropriate world-wide array of 100 systems.
Future Plans
The fact that changes in decay rates of some
radioactive isotopes can precede solar storms by more than a day makes
our technology quite promising. Moreover, it seems likely that this
technology can be combined with other techniques presently being
studied to predict solar flares (See J. Space Weather Space Clim. 3,
A17 (2013), and
http://www.cost.eu/domains_actions/essem/Actions/ES0803]. Our eventual
goal is thus to establish a larger network combining these various
technologies. In that network, the obvious scalability of our system
utilizing radioactive decay measurements is likely to play a
significant role.
Acknowledgements
The authors wish to thank Catherine Ansbro, Eammon Ansbro, Jeff Sinard, John Voeller and Linda Yu for their helpful advice.
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12:15
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SEP Events Conditioned by the Primary Suprathermal Populations
Lazar, Marian; Poedts, Stefaan
KU Leuven, BELGIUM
Here we propose to review the role played by the primary flux
of suprathermal particles, electrons and protons, in the initiation of
flares and CMEs. The existence of a critical level of the suprathermals
is investigated, giving preliminary estimates for the relationship with
the threshold conditions of the wave instabilities responsible for the
particle reacceleration at these sites.
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Posters
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Title
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Daily Normalized Helicity of Subsurface Flows
Komm, Rudolf1; Reinard, Alysha2; Hill, Frank1
1National Solar Observatory, UNITED STATES;
2University of Colorado & NOAA/SWPC, UNITED STATES
Flare-productive active regions are associated with subsurface
flows with large values of kinetic helicity density. Kinetic helicity
is related to mixing and turbulence of fluids. Reinard et al. 2010 have
developed a parameter that captures the variation of kinetic helicity
with depth and time, the so-called Normalized Helicity Gradient
Variance (NHGV). This parameter increases 2-3 days before a flare
occurs and the NHGV values for flaring and non-flaring active regions
represent clearly separate populations. We derive subsurface flows from
the surface to a depth of 16 Mm using GONG Dopplergrams analyzed with
the ring-diagram technique. From the measured velocities, we calculate
kinetic helicity density as a function of position on the solar disk.
We will then calculate the NHGV parameter exploring different
normalization schemes and depth ranges. We will calculate daily NHGV
maps of the solar disk for different levels of magnetic activity. We
will present the latest results.
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2 |
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Groups of Type III Bursts Associated with CME Events at Decameter Wavelengths
Boiko, Anastasiya1; Melnik, Valentin2; Poedts, Stefaan1; Konovalenko, Alexander2; Dorovskyy, Vladimir2
1KU Leuven, BELGIUM;
2Institute of Radio Astronomy, National Academy of Sciences of Ukraine, UKRAINE
We report on the observations of solar type IV bursts and
their precursors, namely groups of type III bursts, in the frequency
range of 8 - 33 MHz. The observational data obtained with the
ground-based radio telescope UTR-2 (Kharkiv, Ukraine) during 2012
campaign completed by spacecrafts data are used. We consider the CMEs
(Coronal Mass Ejections), which correspond to type IV radio bursts, and
electrons, which generate groups of type III radio bursts observed
before type IV bursts, simultaneously originate from the same active
regions. The main properties (frequency drift rate, duration, flux) of
type III and type IV bursts are analyzed. Several physical
characteristics of the CME are estimated.
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3 |
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Lower Hybrid Drift Instability in Coronal Loops
Poedts, Stefaan; Lapenta, Giovanni; Desmet, Natascha
KU Leuven/CmPA, BELGIUM
Almost 70 years after the discovery, the solar coronal heating
puzzle is still one of the major challenges in astrophysics. A
self-consistent coronal heating model must fulfil a lot of requirements
imposed by observational facts. It is commonly accepted that many
mechanisms contribute to the temperature of the solar corona.
However, determining which process dominates in what region, has proven
to be very difficult. Many heating models have already been proposed
for the coronal heating problem, and the two theories that currently
stick out are the theory of wave heating and the theory of magnetic
reconnection. Although a lot of research is still needed on these two
theories, it is very unlikely that they will be able to fully explain
the problem since they rely on the continuum or fluid approximation
(Magnetohydrodynamics, MHD). Hence, these models cannot really explain
coronal heating completely because i) it is clear that the actual
heating takes place at length scales much smaller than those on which
the (macroscopic) MHD model is justified; and ii) it is obvious that
the observed discrepancy between ion and electron temperatures in the
corona, as well as iii) the observed large temperature anisotropy in
the inner corona and iv) the observed preferential heating of the
heavier ions are beyond the (single!) fluid model.
The alternative that is explored here is based on the
kinetic theory of drift waves. Assuming drift waves as the cause of the
coronal heating implicitly states that the energy source of the heating
is located in the corona itself, viz. in the ubiquitous density
gradients present there. Though drift waves are studied intensively in
the context of nuclear fusion research, not much studies are available
on drift waves in solar context. Hence, it is important to look for
methods to confirm the presence of drift waves in e.g. the solar
corona. Here, the Vlasov theory will be used to study the presence of
the lower hybrid drift instability in plasmas with a density gradient
perpendicular to the magnetic field. A new approach for this study of
Vlasov theory will be used. The main idea consists of expanding the
distribution function in a series of Hermite polynomials in velocity
space. This approach will facilitate the interpretation of the results
obtained, as every expansion term has a specific physical meaning. The
study has bot numerical and analytical components in an attempt to
quantify the presence of drift waves in the solar corona and their
contribution to the heating problem.
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4 |
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Proportional Number of Released Near-Relativistic Electrons and SXR
Intensity in Solar Flares
Agueda, Neus1; Sanahuja, Blai1; Vainio, Rami2; Pönni, Arttu2; Klein, Karl-Ludwig3; Rodríguez-Gasén, Rosa3; Vilmer, Nicole3
1University of Barcelona, SPAIN;
2University of Helsinki, FINLAND;
3Paris Observatory, CNRS, FRANCE
We examine the emission of near-relativistic (NR; >50 keV)
electrons during solar flares. NR electron events observed in the
heliosphere by spacecraft such as ACE, Wind or STEREO provide us with
crucial information to unravel the release history of solar energetic
particles (SEPs).
We use inversion methods developed within the EU/FP7
SEPServer project to extract, from directional intensities observed
near 1 AU, the electron release history for a sample of
flare-accelerated events. For each event, we compare the inferred
number of released electrons with the intensity of the associated soft
X-ray (SXR) flare. We find a close proportionality between the
intensity of the SXR flare and the number of released electrons;
correlation coefficient 0.949.
This empirical law is combined with an interplanetary
transport model database of simulation results, publicily available
through the SEPServer website, to predict the expected time of arrival
and the in-situ electron event peak intensities for different flare
sizes. The tool is used to estimate the maximum amount of NR-electron
radiation that solar flares might produce near 1 AU, for an early
warning system of flare-related SEP events.
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5 |
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Which Data? Is Flare Prediction More Efficient through Proxy Quantities, or via Fundamental Physical Parameters?
Georgoulis, Manolis
Academy of Athens, GREECE
Flare-prediction parameters roughly fall into three distinct
classes: proxy parameters, that mostly depend on or quantify the
morphology of the source active region, complexity parameters, that
explore the fractal/multifractal nature of the region, and fundamental
physical parameters, calculated mainly via simplifying assumptions.
Recently, it has been suggested that complexity metrics are not
expected, and seem to be unable, to distinguish between flaring and
non-flaring solar active regions. If this result is further
established, flare prediction must rely on proxy quantities and
physical parameters, namely the free magnetic energy and, for several
models, the magnetic or kinetic helicity of the regions. We examine the
pros and cons of each class of predictors, considering ease and speed
of the calculations and discussing their predictive ability. Relevant
examples are also given. We conclude that the local nature of the
flare-triggering process, plus the lack of information to unambiguously
calculate fundamental physical quantities makes adequately-defined
proxy quantities more efficient for continuous, routine prediction.
However, (1) cutting-edge physical understanding is required to produce
a suitable proxy, and (2) fundamental physical parameters may enclose a
short-term predictive ability for major flares, provided that their
timeseries on a candidate flaring region are properly treated for
various unrelated effects.
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Athens Effective Solar Flare Forecasting (A-EFFort)
Georgoulis, Manolis1; Tziotziou, Konstantinos2; Maneas, Efthymios3; Magiati, Margarita3; Luntama, Juha-Pekka4; Glover, Alexi5
1Academy of Athens, GREECE;
2RCAAM of the Academy of Athens, GREECE;
3BRF of the Academy of Athens, GREECE;
4ESA/ESAC, SPAIN;
5ESA/ESTEC, NETHERLANDS
An online solar-flare forecasting utility is currently
implemented in the premises of the Academy of Athens. Upon completion,
A-EFFort will be used as an ESA federated service in the framework of
the Agency's Space Situational Awareness (SSA) Programme. The core of
the A-EFFort utility comprises two pattern-recognition and
computational-analysis techniques: a proven active-region
identification algorithm (ARIA), used to automatically extract solar
active regions from full-disk line-of-sight magnetograms acquired by
the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics
Observatory (SDO), and an automatic calculation of the effective
connected magnetic field strength (Beff) for each of the identified
active-region patches. From the derived Beff-values and existing
statistics we will provide and validate flare probabilities assigned to
a given forecast window for each active region separately and the
earthward solar hemisphere as a whole. In its nominal operation,
A-EFFort will deliver routine 24-hour forecasts for X-, M-, and C-class
flares updated every three hours. During periods of exceptional solar
activity and enhanced likelihoods of major or great solar flares,
automated electronic messages will be sent to a list of subscribed
service users. Plans for service updates and maintenance are in place
for a number of years after the conclusion of the project's
implementation, aiming to establish A-EFFort as a core tool of the
ESA/SSA method arsenal.
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The NWRA Flare-Forecast Comparison Workshops: Goals, Participants, and Methodology
Leka, K.D.1; Barnes, Graham1; The Int'l Flare Forecasting, Comparison Group2
1NorthWest Research Associates, UNITED STATES;
2N/A, UNITED STATES
Two workshops have been held recently, in 2009 and 2013, to begin
systematic comparisons of methods for forecasting solar flares.
The first, also known as the "All-Clear Forecasting Workshop" was
held jointly with NASA/Space Radiation Analysis Group and NOAA/Space
Weather Prediction Center, had a focus on predicting "All-Clear periods"
from the standpoint of major flares and solar energetic particle events.
The second more recent workshop, held at NorthWest Research Associates
in Boulder, CO, USA, focused on using and exploiting the recent data from
the NASA/Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager
(HMI), particularly the vector magnetic field time-series now available.
For both workshops, many researchers active in flare-forecasting research
participated, and diverse methods were represented in terms of both how
the methods characterize the Sun, and the statistical approaches used
to create a forecast. We describe here the goals of both workshops,
the participating methods, and the approaches developed for allowing
standardized, testable comparisons between methods.
(Funding for the workshops and the data analysis was provided by NASA/Living
with a Star contract NNH09CE72C and NASA/Guest Investigator contract
NNH12CG10C.)
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8 |
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Spatial Distribution of the Magnetic Helicity Flux in a Flaring Site
Romano, Paolo1; Zuccarello, Francesca2
1INAF - Catania Astrophysical Observatory, ITALY;
2Dipartimento di Fisica e Astronomia - Catania University, ITALY
We use HMI/SDO line-of-sight magnetograms to analyze the
spatial distribution of the magnetic helicity flux in active region
(AR) NOAA 11283. Applying an algorithm to identify areas characterized
by similar magnetic helicity flux in sign, we determine how fragmented
was the helicity flux in the active region. The results clearly show
that areas characterized by the lower difference in the number of
patches with helicity flux of opposite sign are the most favourable for
eruptive events occurrence.
We also show that flares and CMEs occurred in this AR
are linked to the interaction between magnetic systems characterized by
opposite sign of magnetic helicity flux.
The research leading to these results has received
funding from the European Commissions Seventh Framework Programme under
the grant agreement no. 284461 (eHEROES project).
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9 |
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Predicting Flaring Activity through Supervised Classification on Predictor Variables
De Visscher, Ruben; Delouille, Veronique
Royal Observatory of Belgium, BELGIUM
Recent years have seen a resurgence in the field of solar flare prediction.
Most of these methods aim at evaluating a flare
probability in the next 24h based on the current or past status of an
active region.
In this project sequences of magnetogram and continuum
images are used to distinguish active regions with strong flaring
activity.
A homogeneous dataset of magnetogram and continuum images of active regions in their growth phase is produced.
These images are summarized into various scalar
predictor variables, which are used as the input for the supervised
classification methods.
These methods take into account the time evolution of the active regions through lagged values of the predictors.
The performance of various supervised classification
algorithms as well as the predictive power of each predictor variable
are assessed.
Special care is taken to handle the imbalance between the number of active regions with and without strong flaring activity.
In our poster we will discuss preliminary results from this project.
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10 |
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Acceleration and Solar Origin of Solar Energetic Particles Observed by SREM Units
Anastasiadis, Anastasios1; Georgoulis, Manolis2; Daglis, Ioannis A.3; Sandberg, Ingmar1; Nieminen, Petteri4
1National Observatory of Athens, GREECE;
2Academy of Athens/ RCAAM, GREECE;
3National Observatory of Athens and Department of Physics, University of Athens, GREECE;
4ESA/ESTEC, NETHERLANDS
Within the previous solar cycle 23, SREM units onboard ESA's
INTEGRAL and Rosetta spacecraft detected several tens of Solar
Energetic Particle Events (SEPEs) and accurately pinpointed their
onset, rise, and decay times. We have undertaken a detailed study to
determine the solar sources and the subsequent interplanetary coronal
mass ejections (ICMEs) that gave rise to these events, as well as the
timing of SEPEs with regard to the onset of possible geomagnetic
activity triggered by these ICMEs. We find that virtually all SREM
SEPEs can be associated with CME-driven shocks. Moreover, for a number
of well-studied INTEGRAL/SREM SEPEs we see an association between the
SEPE peak and the shock passage at L1, subject to the heliographic
location of the source solar active region. Shortly after the SEPE peak
(typically within a few hours), the ICME-driven modulation of the
magnetosphere kicks in, often associated with a dip of the Dst index,
indicating storm conditions in geospace. In essence we find that SREM
SEPEs can be seamlessly fit into a coherent and consistent
heliophysical interpretation of solar eruptions all the way from Sun to
Earth. Their contribution to space-weather forecasting may be
significant and warrants additional investigation.
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Correlation of Solar Flares with Long-Term Irradiance and Sunspot Levels
Dammasch, Ingolf; Dominique, Marie
Royal Observatory of Belgium, BELGIUM
For more than three years, the radiometer LYRA on the ESA
micro-satellite PROBA2 has been observing the Sun in the ultraviolet
and gained a considerable data base. On its websites, LYRA presents not
only EUV and SXR time series in near real-time, but also information on
flare parameters and long-term irradiance and sunspot levels. It will
be discussed how these parameters correlate, and whether it is possible
to aid space weather forecast with these statistical data, especially
for the prediction of expected flare strength.
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Torus Instability and Filament Eruptions: An Observational Investigation
Zuccarello, Francesco1; Seaton, Daniel2; Mierla , Marilena2; Berghmans, David2; Poedts, Stefaan1; Romano, Paolo3; Zuccarello, Francesca4
1CmPA / KU Leuven, BELGIUM;
2Royal Observatory of Belgium, BELGIUM;
3INAF - Catania Astrophysical Observatory, ITALY;
4University of Catania, ITALY
Several models have been proposed to explain the initiation of
CMEs. However, which model better explains the different aspects of the
initiation process and the early evolution of the CMEs is a subject of
ongoing discussion.
Using the vantage points of the STEREO spacecraft we
reconstruct the three-dimensional position of the erupting structure,
while the magnetic field evolution is used in order to identify
eventual persistent photospheric plasma flows and/or the emergence of
new magnetic flux. Finally, potential field extrapolations are used to
determine the stability properties of the relevant active region and to
disentangle which is the driver of the investigated eruption.
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Space Weather and Ultraviolet Solar Variability (SWUSV) Microsatellite Mission: Prediction of Major Flares and CMEs
Damé, Luc
LATMOS/IPSL/CNRS/UVSQ, FRANCE
We present the Space Weather and Ultraviolet Solar Variability
(SWUSV) Microsatellite Mission proposed to ESA and CNES for a
better/earlier prediction of major flares and CMEs and their
geoeffectiveness. Mission is an evolution of PROBA-2 and PICARD based
on high cadence imaging of the solar disk in Lyman Alpha coupled to
H-Alpha from ground network. Objectives, payload and mission, based on
a MYRIADE Evolution platform, will be described. Mission is under
consideration by CNES in its prospective exercise and could be in
service as early as 2018.
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Towards a Predictive Model for SEPs
Linker, Jon1; Schwadron, Nathan2; Torok, Tibor1; Gorby, Matthew2; Downs, Cooper1; Lionello, Roberto1; Falconer, David3; Mikic, Zoran1; Riley, Pete1
1Predictive Science Inc, UNITED STATES;
2University of New Hampshire, UNITED STATES;
3University of Alabama, Huntsville, UNITED STATES
Solar energetic particles (SEPs) are an important space
weather phenomena. SEPs can damage satellite instrumentation, and they
can be hazardous for crews of Low Earth Orbit spacecraft and the
International Space Station, especially when engaged in extravehicular
activity. They also represent a significant risk to crews of future
manned lunar or interplanetary missions. SEPs are one of the most
difficult phenomena to predict: their generation and propagation spans
very different plasma regimes and large regions of the heliosphere.
Successful prediction will ultimately involve many elements: prediction
of flares/CMEs prior to eruption, simulating CMEs and associated
shocks, and modeling SEP acceleration and propagation. In this paper,
we describe an approach to this problem that combines empirical and
physics-based models. We discuss how, given a prediction for a
flare/CME, CMEs can be modeled in the corona and inner heliosphere. We
show initial results for SEP fluxes generated from coupled CME/SEP
modeling.
Research supported by NSF and NASA.
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A Space Weather Service for Solar Flare Forecasting
Tranquille, Cecil1; Wheatland, Mike2; Lawrence, Gareth1
1RHEA System S.A., BELGIUM;
2University of Sydney, AUSTRALIA
We report on the re-implementation of the Wheatland (2004,
2005) solar flare prediction model as an active online space weather
service for the daily prediction of GEOS X-ray flares. The model uses a
Bayesian approach to predict solar flare activity based on a database
of event statistics from GOES measurements spanning over almost 40
years. This approach has the advantage of being objective without the
need for users to make ad hoc assumptions. It uses only the past
history soft X-ray flare events, and the statistical rules of solar
flare occurrence.
We use the model to retrospectively validate M- and
X-class event occurrence rates for periods of past solar activity, and
also illustrate the results of the online prediction service running
daily flare predictions for the present phase of this solar cycle. We
also investigate the use of Bayesian analysis to predict occurrence
rates for solar energetic particle events, given the similarity of the
statistical properties of events for flares and energetic particles.
Wheatland, M.S., A Bayesian approach to solar flare prediction, Astrophys. J., 609, 2004.
Wheatland, M.S., A statistical solar flare forecast method, Space Weather, 3, 2005.
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Solar Eruptions observed by the AIA and SECCHI on Board the SDO and STEREO.
Chmielewska, Ewa; Tomczak, Micha³; Ko³omañski, Sylwester
Astronomical Institute, University of Wroclaw, POLAND
In this study we focus on the analysis of the early phase of
flares initiation associated with the CMEs. The aim of this work is to
determine kinematical properties and important structural components of
these solar eruptions. We analyzed multi-thermal observations of
eruptive plasmoids associated with coronal mass ejections and/or flares
using the data recorded by the Atmospheric Imaging Assembly (AIA) on
board the Solar Dynamics Observatory (SDO).
The six coronal EUV channels, high spatial and temporal resolution and
large field of view provide us the opportunity for verifying the
existing models of solar eruptions. In addition, in order to observe
the further propagation of these solar eruptive phenomena in the
heliosphere we also use data taken by Sun Earth Connection Coronal and
Heliospheric Investigation (SECCHI) on board the Solar TErrestrial RElations Observatory (STEREO).
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On the origin of solar energetic particles
Miteva, Rositsa1; Klein, Karl-Ludwig1; Samwel, Susan2; Reid, Hamish3; Nindos, Alexander4; Kouloumvakos, Athanasios4
1LESIA-Observatoire de Paris, FRANCE;
2National Research Institute of Astronomy and Geophysics, EGYPT;
3University of Glasgow, UNITED KINGDOM;
4University of Ioannina, GREECE
The aim of this study is to identify the solar origin (flares
vs. CMEs) of the solar energetic particles observed during solar cycle
23. For each SEP event, a flare and CME candidate was found by
searching into specific temporal and spatial window. A pre-selection of
SEPs associated with X and M-class flares was done and thus 180 events
in total were analyzed. In order to argue in favor of flare, CME or
mixed contribution to the escaping particle fluxes, we utilized all
available dynamic radio spectral and single frequency radio (RSTN)
records. Our analysis shows that about half of all SEP events are
accompanied by high-frequency radio emission signatures that argues in
favor of flare acceleration. Less than a third of the events show radio
signatures from the high corona only and/or confinement.
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Solar UV Emission as a possible Reason of long-term Preflare Fluctuations in H-Component of the Geomagnetic Field
Sheiner, Olga; Smirnova, Anna; Snegirev, Sergey
Radiophysical Research Institute, RUSSIAN FEDERATION
It was shown before that long-term fluctuations of geomagnetic
field can be considered as prognostic parameter for solar proton
flares. This paper is devoted to the comparison of pre-flare behavior
of long-term spectral components in the spectrum of the solar
ultraviolet radiation and the horizontal component of the geomagnetic
field. This study is based on wavelet spectra of solar ultraviolet
emission during the period preceding solar proton flares. It is found
the congruence in the behavior of spectral components with periods of
30-60 minutes in the ground-based measurements and in UV emission for
3-1 days before the proton flare.
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