Session 9 - Satellite observations of the thermosphere-ionosphere contributing to Space Weather products and forecasting capabilities

Guram Kervalishvili (GFZ German Research Centre for Geosciences), Eelco Doornbos (TU Delft)
Wednesday 7/11, 11:15-12:45
MTC 01.03

The session aims to provide the possibility to present and discuss contributions on the use of data from Earth-orbiting satellites making measurements in the thermosphere-ionosphere, to space weather relevant products. Data from LEO satellites can help to provide a global view of space weather variability and is therefore complementary to data from ground-based observations, which have limited global coverage. A true global picture of Space Weather, in which regional effects can be put into a global context, can be obtained from the combination of space and ground assets. The AMPERE project and integration of relevant Swarm mission data into ESA’s Space Weather program are current examples of this. The availability of thermosphere and ionosphere data obtained from the GRACE and GOCE missions demonstrate that also satellites that are not dedicated to space weather or space physics can still bring valuable contributions to these fields. NASA’s ICON and GOLD missions, as well as the proposed ESA D3S initiative and various CubeSat programs, could provide similar or enhanced space weather products with new capabilities for space weather monitoring and prediction in the near-future.

We solicit contributions that introduce relevant activities, on topics ranging from data processing, data-assimilation in models and Space Weather case studies to descriptions of existing and future Space Weather products and satellite mission concepts.

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Talks : Time schedule

Wednesday November 7, 11:15 - 12:45, MTC 01.03

11:15	Daedalus: A Low-Flying Spacecraft for the Exploration of the Lower Thermosphere - Ionosphere	Sarris, T et al.	Invited Oral
	Theodoros Sarris[1], Errico Armandillo[2], Vaios Lappas[3], Iannis Dandouras[4], Minna Palmroth[5], David Malaspina[6], Allison Jaynes[7], Guram Kervalishvili[8], Anita Aikio[9], Stephan Buchert[10], Mark Clilverd[11], Christopher Cully[12], Konstantinos Kourtidis[13], Nikolaos Paschalidis[14], Jasper Halekas[5], John Sample[16], Ingmar Sandberg[17], Qian Wu[18], Anna Belehaki[19],
	We present a proposed mission concept, Daedalus, targeting to quantify key electrodynamics processes that determine the structure and composition of the upper atmosphere, the gateway between the Earth’s atmosphere and space. An innovative mission design allows Daedalus to break through the current spacecraft exploration “barrier” of 150 km and access electrodynamics processes at lower altitudes. Daedalus will perform in-situ measurements of plasma density and temperature, ion drift, neutral density and wind, ion and neutral composition, electric and magnetic fields. These measurements will unambiguously quantify the amount of energy deposited in the upper atmosphere during active and quiet geomagnetic times via Joule heating and Energetic Particle Precipitation, estimates of which currently vary by orders of magnitude between models. An innovation of the Daedalus mission concept is that it includes the release of sub-satellites at low altitudes: combined with the main spacecraft, these sub-satellites will provide multi-point measurements throughout the Lower Thermosphere-Ionosphere region at high latitudes, down to altitudes below 120 km, in the heart of the most under-explored region in the Earth’s atmosphere.
11:30	Space weather and geospace research with ESA's Swarm constellation: results, perspectives and opportunities	Floberghagen, R et al.	Invited Oral
	Rune Floberghagen and many members of the Swarm team
	Directorate of Earth Observation Programmes, European Space Agency, Frascati, Italy
	The Earth-orbiting four-satellite Swarm constellation continuously delivers high-quality data on the magnetosphere-ionosphere-thermosphere region through in-situ measurements of the magnetic field vector, the ionospheric plasma environment and thermospheric neutral density. This contribution first highlights examples of current research and services utilising Swarm and affiliated data, and furthermore provides an outlook into the future of Swarm in the context of solar-terrestrial physics and space weather. It also aims to describe the mission’s initial steps towards improving the observation and understanding of the link between terrestrial weather phenomena and weather in space. Following in the footsteps of the CHAMP mission and aiming for a long on-orbit lifetime, Swarm extends the available magnetic field, ionosphere and thermosphere data into the next solar cycle, and for the first time provides multi-point/multi-payload measurements of this environment. These observations enable a broad variety of investigations of the response of the thermosphere to energy inputs and cooling processes over a wide range of external conditions. Likewise, the high-accuracy magnetic and electric field data of the Swarm satellites contribute to improved climatological models of the high-latitude current system and energy exchange. In addition, the high temporal resolution of these measurements enables the investigation of the plasma environment at much smaller scales than has been possible before, unravelling details on the relationship between small and large scale currents. As such, the comprehensive set of observations acquired by Swarm, including simultaneous observations of B, E, plasma temperature and density, ion flow and neutrals provide a powerful toolbox for the community, and for aeronomy and solar-terrestrial physics in particular. Based on a highly successful four-year nominal mission Swarm has recently received an extension. All three satellites are in excellent overall health and carry sufficient propellant for a prolonged on-orbit lifetime. Mission stakeholders are enthusiastically continuing to invest in improving its data products and implementing a broad earth system science and applications agenda. Further improvement and development of space weather applications based on Swarm and affiliated data are key to this endeavour.
11:45	Ionospheric information obtained from ELF whistlers detected by the ESA Swarm satellites	Coïsson, P et al.	Oral
	Pierdavide Coïsson[1], Pierre Deram[1], Gauthier Hulot[1], Pierre Vigneron[1], Jean-Michel Léger[2], Thomas Jager[2]
	[1] Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS/INSU, Paris, France, [2] CEA, Léti, MINATEC Campus, Grenoble, France
	Lightning strikes generate broadband electromagnetic signals that propagate into the atmosphere and can reach into the ionosphere. Dispersion of the waves within the ionosphere generates a frequency dependent propagation time, producing whistler signals. At ELF frequencies the signal dispersion and the cutoff frequency depend on ions composition and their gyrofrequencies. The frequencies below 125 Hz thus provide additional information on the ionospheric status not accessible from other frequency bands. During the commissioning phase of the Swarm mission several burst-mode sessions of the Absolute Scalar Magnetometers (ASM) were operated between December 2013 and February 2014, during which the sampling frequency was raised from the nominal 1 Hz to 250 Hz. A large number of whistlers in the ELF frequency band were obtained during these sessions, associated with the lightning activity in the troposphere. By correlating the whistlers with ground-detected lightnings from the World Wide Lightning Location Network, we were able to study the lightning detection efficiency at Swarm altitude. By taking advantage of the simultaneous electron density measurements made by Swarm, we were also able to study the dependence of the whistler dispersion with the ionospheric and geomagnetic conditions encountered by the satellites. This appears to provide new way to derive information on the electron and ion density profiles over areas where no other measurements are available. As we shall illustrate, this information could in turn be used to better constrain ionospheric models such as IRI and NeQuick. New regular ASM burst-mode sessions are now planned for the rest of the Swarm mission that will provide additional data valuable for the investigation of the ionosphere below the satellites.
12:00	DTM2018 in the framework of the H2020 project SWAMI	Bruinsma, S et al.	Oral
	Sean Bruinsma
	CNES, Space Geodesy Office, Toulouse, France
	In the framework of the H2020 project SWAMI funded by the European Commission (EC), which started in January 2018, a new whole atmosphere model (0-1500 km) is under development. The model will be constructed by blending two existing models, the Drag Temperature Model (DTM) and the Unified Model (UM). The CNES thermosphere specification model DTM2013, which was developed in a previous EC project (ATMOP), is being improved by assimilating more density data to drive down remaining biases as a function of solar activity and seasons mainly. The intermediate model DTM2018, which is still based on the Kp index, is the topic of this presentation. The final DTM model will be constructed in 2019 using high cadence geomagnetic indices (so-called Hp indices), which will require algorithm modification and determination of optimum delays and such. The development of DTM2018 is done according to a new strategy, which includes testing of: - scaling density datasets (e.g., GOCE density V1.5 as provided, or scaled to HASDM), - not assimilating all datasets (e.g. no spectrometer data, no SwarmA data, etc), - iterative development (enhancing the model for a specific effect/variation per iteration) A short review of the DTM model and the assimilated data will be given, and DTM2013 and DTM2018 performance is evaluated by comparisons with data.
12:15	Observation of traveling ionospheric disturbances with ICON ultraviolet imagers	Wautelet, G et al.	Oral
	Gilles Wautelet, Benoît Hubert, Jean-Claude Gérard
	LPAP, STAR institute, Liège University (Belgium)
	Atmospheric gravity waves transfer energy and momentum from the lower atmosphere to the thermosphere. Due to the exponential decay of the atmospheric density, their amplitude grows with increasing altitude and their motion is transferred to ions and electron, making them observable in the ionospheric ion or electron density to give the so-called classical Traveling Ionospheric Disturbances (TIDs). The two ultraviolet airglow imagers, FUV (135.6 nm) and EUV (61.7 and 83.4 nm), onboard the upcoming NASA’s ICON mission will remotely sense the ionosphere from its bottom up to the altitude of the spacecraft to retrieve electron density profiles by performing limb scanning. With an inclination of 27° and a circular orbit at an altitude of 550 km, the ICON mission will focus on low latitudes only. The viewing geometry of EUV and FUV is very similar: 12s sampling rate, vertical field of view of 24°, with a similar viewing direction. The purpose of the work is to analyze the geometrical conditions, which will be considered as identical for both instruments, that can enhance or prevent the observation of TIDs with ICON, based on simulations only. The simulation relies on an ionospheric and geomagnetic background (IRI and IGRF) on which we superimpose TIDs of variable characteristics such as propagation azimuth, period, horizontal wavelength and velocity. We simulate line-of-sight integrated values of the electron density, called Total Electron Content (TEC), and consider this physical quantity as a proxy of Level-1 products of ICON EUV/FUV instruments. Then, we investigate the optimal and worst conditions to observe TIDs with ICON and attempt to retrieve their characteristics based on images and time series of TEC simulations.
12:30	European SpaceCraft for the study of Atmospheric Particle Escape: follow-on mission	Dandouras, I et al.	Oral
	Iannis Dandouras[1], Masatoshi Yamauchi[2], Henri Rème[1], Johan De Keyser[3], Octav Marghitu[4], Masafumi Hirahara[5]
	[1] Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse/CNRS/CNES, Toulouse, France, [2] Swedish Institute of Space Physics, Kiruna, Sweden, [3] Royal Belgian Institute for Space Aeronomy, Brussels, Belgium, [4] Institute for Space Sciences, Bucharest-Magurele, Romania, [5] ISEE, Nagoya University, Japan
	Recent studies using Cluster hot ion data show that the ionospheric ion escape in the past was large enough to affect the evolution of the terrestrial atmosphere and life on a geological time scale, with a Kp dependence of ~ exp(0.45*Kp) or higher. Assuming the ancient solar and interplanetary conditions were equivalent to present Kp = 9 – 10 conditions, the total atmospheric escape over 4 billion years is as much as the total atmospheric mass of the present Earth. Also a recent study on the mass-loading effect by these escaping ions predicts the same exponential dependence on the solar wind energy extraction, indicating this type of "exponential" energy extraction from the solar wind might become more significant than the reconnection, which is only linear to the coupling parameter (e.g. Akasou's epsilon). Thus atmospheric escape is potentially important even for the space weather problem. Unfortunately, our present knowledge on the atmospheric escape is very limited. This is partly because the knowledge on the exosphere is very poor for both ions and neutrals (poor knowledge of densities and substantially no knowledge on velocity distributions), and partly because we do not know well about how the incident energy is distributed and how the ions and neutrals are lifted up there. To quantitatively estimate the amount of escape of the major atmospheric components (nitrogen and oxygen) as neutral and ionised species, over a geological time scale, the "ESCAPE" (European SpaceCraft for the study of Atmospheric Particle Escape) mission was proposed in response to the ESA-M5 call. The mission has been designed to combine in-situ direct particle measurements and optical remote-sensing measurements and make the following first-time systematic observations ever: (1) the spatial distribution of the each species of the neutral atmosphere (density, temperature and altitude profiles); (2) isotope ratios of the major neutral and ion species; and (3) ion-neutral ratios (substantial ionization rate) of major species, in an extended altitude range from the exobase/upper ionosphere (500 km altitude) up to the magnetosphere. The result was to be used as a reference to understand the atmospheric/ionospheric evolution of magnetized planets, and to also contribute to many topics in space sciences, e.g., to be used as a reference in understanding optical observations of the atmospheres of the exoplanets. Although the proposal was not selected for M5, the importance of the objective is increasing with recent studies (the very recent 52nd ESLAB Symposium is just an example), and we are considering a down-scaled mission, hopefully in cooperation with other missions such as a Japanese formation flight mission or a D3S mission. A downscaled version of the ESCAPE mission will be presented.

Posters

1	Spherical calibration method on atmospheric density model calibration	Luo, B et al.	p-Poster
	Y. Zhu[1], S. Yang[1], T. Ren[2], J. Miao[2], S. Liu[2], B. Luo[2]
	[1]China Xi’an Satellite Control Center, [2]National Space Science Center, Chinese Academy of Sciences
	Making calibration on atmospheric model density is an important way to improve the accuracy of atmospheric model. This paper make a calibration on NRLMSISE-00 using a spherical method with the atmospheric density data derived from high-accuracy accelerometer onboard satellite CHAMP. First we assimilate atmospheric density to a same altitude, then calculate the inner and outer precision based on the calibration results. Result shows that the inner and outer precision reduced significantly after spherical calibration. To be specific, the inner precision reduced to about 10% during high year of solar activity, and prediction accuracy improved by 31.34%, 21.39%, 13.75% on 1, 2, 3 days in advance; the outer precision reduced to about 14% during low year of solar activity, and prediction accuracy improved by 55.03%, 47.79%, 43.60% on 1, 2, 3 days in advance.
2	The Extended Unified Model – a new non-hydrostatic model for the thermosphere	Jackson, D et al.	p-Poster
	David Jackson[1], Emily Down[1], James Manners[1], Dan Griffin[2], Matt Griffith[3], Chris Kelly[4], Sean Bruinsma[5], Sandra Negrin[6], Claudia Stolle[7]
	[1] Met Office, UK, [2] University of Exeter, UK, [3] University of Bath, UK, [4] University of Leeds, UK, [5] CNES, France, [6] Deimos, Spain, [7] GFZ, Germany
	‘Space Weather Atmosphere Model and Indices’ (SWAMI) is a new Horizon 2020 project which aims to enhance the understanding of space weather processes and their impact on atmospheric density. A chief objective is to develop a unique new whole atmosphere model, by extending and blending the physics-based Unified Model (UM), and the semi-empirical Drag Temperature Model (DTM), which are leading models of their kind in the field. Together with improved nowcasts and forecasts of the Kp index (and equivalent higher cadence indices), the whole atmosphere model shall be the basis of enhanced user-focused tools for satellite orbital prediction, launch and re-entry operations. The presentation shall focus on the development of the extended UM. The UM currently spans the 0-85 km altitude range, and is used for weather forecasts and climate studies at the Met Office, but its dynamical setup makes it potentially very well suited to the thermosphere, too. The initial goal is to raise the UM upper boundary to around 150-170 km. Much work shall focus on radiative transfer. This includes implementation of a non-local thermodynamic equilibrium scheme for more accurate heating rates above 70 km in altitude, and development of new ultraviolet and extreme ultraviolet radiation schemes. The latter will provide photolysis rates which will be input into a new thermospheric chemistry scheme. Associated work on analysing and improving the UM robustness in the lower thermosphere shall also be discussed, in addition to initial work focused on developing the UM for use in the entire thermosphere.
3	Use of GNSS to augment foF2 modelling	Bouya, Z et al.	p-Poster
	Z. Bouya, V. Kumar, M. Terkildsen, P. Maher, G. Patterson
	Space Weather Services, Australian Bureau of Meteorology, Sydney, Australia
	This paper proposes a new approach to investigating the possibility of estimating foF2 from Total Electron Content(TEC). In this work, GNSS measurements which provide another measure of ionosphere characteristics will be incorporated to augment foF2 modelling and forecasting applicable to geographic locations where measured data are not readily available. A Canonical correlation Analysis (CCA) model using archived TEC, foF2 data and updated with real time GPS observations was used. This study commenced with three stations around Australia; Darwin, Canberra and Hobart with promising results and will be applied to other stations. By performing this analysis, it will be possible to addresses the issues of outliers, missing information and fill in gaps in foF2 data.
4	Discrimination between Internal and External origin contributions from LEO satellite magnetic field data.	Piersanti, M et al.	p-Poster
	Mirko Piersanti[1], Massimo Materassi[3], Luca Spogli[4], Antonio Cicone[5], Igor Bertello[2], Piero Diego[2], Pietro Ubertini[2].
	[1]National Institute of Nuclear Physics, University of Rome Tor Vergata, Rome, Italy, [2]Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy, [3]Institute for Complex System, CNR-ISC, Florence, Italy, [4]Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy, [5]DISIM, Università degli Studi dell’Aquila, L’Aquila, Italy.
	The evaluation of the external origin contribution (BEXT and EEXT) in geomagnetic field satellite observations in the near Earth location (1.2 RE
5	On the use of a CubeSats UHF modulated beacon for characterisation of small-scale ionospheric disturbances	Mckenna, E et al.	p-Poster
	E. McKenna[1], M. J. Angling[1], J. Subash[1], G. Minelli[2], J. Newman[2], P. A. Bernhardt[3]
	[1]University of Birmingham, UK, [2]Naval Postgraduate School, USA, [3]Naval Research Laboratory, USA
	Society is increasingly dependent on communications and satellite communication (satcom) is often used where terrestrial infrastructure is under-developed. The choice of radio frequency is dependent on various factors, but UHF is popular because of the low cost of the user terminals, its capability to operate with small and portable antennas, and its resilience to shadowing. The capacity of contemporary UHF satcom is low and is limited by the simple waveforms employed. To overcome this, wideband waveforms are being considered; however, our limited understanding of the distorting effects of the Earth’s ionosphere is a barrier to their development. Such ionospheric distortions are prevalent at high and particularly at low latitudes where ionospheric irregularities cause rapid changes in a signal delay, phase and amplitude. Previous satellite based, trans-ionospheric studies of UHF ionospheric effects have largely been limited to narrowband measurements (i.e. measurements with bandwidths of less than the channel’s coherency bandwidth) and so have not been able to measure multipath effects. PropCube 3 (Merryweather) is one of a series of three 1U CubeSats (i.e. satellites measuring 10×10×10 cm) which is being operated by the Naval Postgraduate School (NPS). It was launched into a 64° inclination, 660 km orbit, in 2015. PropCube can transmit CW (i.e. unmodulated) signals to perform dual/tri frequency ionospheric total electron content (TEC) measurements using standard differential phase techniques. However, the ionospheric time varying channel complex impulse response (CIR) can also be investigated using a modulated beacon. For this work, we have used PropCube’s UHF beacon. This is centred at 380 MHz and comprises a repeating set of eight binary phase shift key (BPSK) modulated pseudorandom noise (PN) codes. Each PN code is 106 chips long and is transmitted at a chip rate of approximately 1 MHz. The beacon is low power (approximately 30 dBm) so processing gain (60 dB) arising from the PN pulse compression is required to retrieve the signal. The PropCube beacon has been received using a mobile ground station on Cape Verde (16.8°N, 25.0°W) in the Atlantic Ocean. The processing of the PropCube signal presents some difficulties since its length (~1 s) results in a very low tolerance to Doppler shifts. This paper will describe the analysis of the PropCube UHF beacon and present initial analysis of the complex impulse response (CIR) of the ionosphere.
6	Ionospheric variability over equatorial latitude during extreme low solar activity period	Purohit, D et al.	p-Poster
	Roshni Atulkar, P.K.Purohit
	National Institute of Technical Teachers' Training and Research, Bhopal – 462002, MP, India.
	The most important ionospheric parameter total electron content (TEC), derived by analyzing dual frequency signals from the Global Positioning System (GPS) recorded near the Indian equatorial anomaly region, Bengaluru (13.020 N, 77.570E) located within 0 - 15oN of the equatorial anomaly region. We studied Diurnal, monthly, seasonal and annual variability as well as geomagnetic and solar effects on the equatorial ionospheric anomaly (EIA) during the solar minimum period from January 2009 to December 2009. The monthly highest values of TEC are recorded during the March, April and October While the minimum TEC is observed during the month of June, July, December and January. Similarly, it is found that the daily maximum TEC near equatorial anomaly crest yield their maximum values for the period of the equinox months and their minimum values during the summer. Using monthly averaged peak magnitude of TEC, a clear semi-annual variation is seen with two maxima occurring in both spring and autumn. Relative standard deviation for VTEC shows high value at around morning and before sunrise. From the comparison of GPS-TEC with different solar indices, i.e. solar EUV flux(0.1–50 nm and 26–34 nm), F10.7 cm solar radio flux and Zurich sunspot number (SSN), it is concluded that the solar index EUV flux is a better controller of GPS-TEC, compared to F10.7 cm and SSN.
7	On the use of topside RO derived electron density for model validation	Shaikh, M et al.	p-Poster
	Muhammad Mubasshir Shaikh[1][4], Bruno Nava[2], Haris Haralambous[3]
	[1] Department of Applied Physics and Astronomy, University of Sharjah, [2] T/ICT4D Laboratory, International Center for Theoretical Physics, [3] Department of Electrical Engineering, Frederick University, Nicosia, Cyprus, [4] Ionospheric Laboratory, Sharjah Center for Astronomy and Space Sciences
	In this work, the standard Abel inversion has been exploited as a powerful observation tool which may be helpful to model the topside of the ionosphere and therefore to validate ionospheric models. A thorough investigation on the behavior of Radio Occultation (RO) derived topside electron density (Ne(h))-profiles has therefore been performed with the main purpose to understand whether it is possible to predict the accuracy of a single RO-retrieved topside by comparing the peak density and height of the retrieved profile to the true values. As a first step, a simulation study based on the use of the NeQuick2 model has been performed to show that, when the RO derived electron density peak and height match the true peak values, the full topside Ne(h)-profile may be considered accurate. In order to validate this hypothesis with experimental data, electron density profiles obtained from four different incoherent scatter radars have therefore been considered together with co-located RO-derived Ne(h)-profile. The evidence presented in this paper show that in all cases examined, if the ISR and the corresponding co-located RO profile have matching peak parameter values, their topsides are in very good agreement. The simulation results presented in this work also highlighted the importance of considering the occultation plane azimuth while inverting RO data to obtain Ne(h)-profile. In particular, they have indicated that there is a preferred range of azimuths of the occultation plane (80o – 100o) for which the difference between the "true" and the RO-retrieved Ne(h)-profile in the topside is generally minimal.
8	Update on thermospheric density products from satellite observations	March, G et al.	p-Poster
	Günther March[1],Tim Visser[1],Eelco Doornbos[1],Elisabetta Iorfida[1],Jose van den IJssel[1],Pieter Visser[1]
	[1]Delft University of Technology, Faculty of Aerospace Engineering, Kluyverweg 1, 2629 HS, Delft, The Netherlands
	Thermospheric data collected by satellites observations has improved our knowledge of atmospheric dynamics and coupling processes in the thermosphere-ionosphere region. However, so far, the differences between data sets and models have been generally ignored or adjusted using ad hoc scale factors. To a large extent, the origin of these discrepancies arises from errors in the aerodynamic modelling of the satellite geometry and of gas-surface interactions (GSI). Using high fidelity geometry models, it is possible to explain part of these differences and to improve our understanding of the atmospheric physics. In this presentation, the latest improvements to satellite geometries and particle-surface collision modelling, and their effect on the newly derived thermospheric products are discussed. Thermospheric density data sets from CHAMP, GRACE, GOCE and Swarm missions are compared with available models leading to more consistent density estimates. The updated products are expected to be useful to the thermosphere-ionosphere science community further increasing the understanding of atmospheric dynamics and long-term trends.
9	An initial ULF wave index derived from 2 years of Swarm observations	Balasis, G et al.	p-Poster
	Georgios Balasis[1], Constantinos Papadimitriou[1]
	[1]National Observatory of Athens
	The ongoing Swarm satellite mission provides an opportunity for better knowledge of the near-Earth electromagnetic environment. Herein, we use a new methodological approach for the detection and classification of ultra low frequency (ULF) wave events observed by Swarm based on an existing time-frequency analysis (TFA) tool and utilizing a state-of-the-art high-resolution magnetic field model and Swarm Level 2 products (i.e., field-aligned currents – FACs – and the Ionospheric Bubble Index – IBI). We present maps of the dependence of ULF wave power with magnetic latitude and magnetic local time (MLT) as well as geographic latitude and longitude from the three satellites at their different locations in low-Earth orbit (LEO) for a period spanning 2 years after the constellation's final configuration. We show that the inclusion of the Swarm single-spacecraft FAC product in our analysis eliminates all the wave activity at high altitudes, which is physically unrealistic. Moreover, we derive a Swarm orbit-by-orbit Pc3 wave (20–100 MHz) index for the topside ionosphere and compare its values with the corresponding variations of solar wind variables and geomagnetic activity indices. This is the first attempt, to our knowledge, to derive a ULF wave index from LEO satellite data. The technique can be potentially used to define a new Level 2 product from the mission, the Swarm ULF wave index, which would be suitable for space weather applications.
11	Evidence of tropospheric 90-day oscillations in the thermosphere	Gasperini, F et al.	p-Poster
	Federico Gasperini[1], Maura E. Hagan[2], Yucheng Zhao[3]
	[1] National Center for Atmospheric Research, [2] Utah State University, [3] Utah State University
	In the last decade evidence demonstrated that terrestrial weather greatly impacts the dynamics and mean state of the thermosphere via small-scale gravity waves and global-scale solar tidal propagation and dissipation effects. While observations have shown significant intra-seasonal variability in the upper mesospheric mean winds, relatively little is known about this variability at satellite altitudes (c.a., 250-400 km). Using cross-track wind measurements from the CHAMP and GOCE satellites, winds from a MERRA/TIME-CGM simulation, and outgoing long-wave radiation (OLR) data, we demonstrate the existence of a prominent and global-scale 90-day oscillation in the thermospheric zonal mean winds and in the diurnal eastward-propagating tide with zonal wavenumber 3 (DE3) during 2009-2010 and present evidence of its connection to variability in tropospheric convective activity. This study suggests that strong coupling between the troposphere and the thermosphere occurs on intra-seasonal timescales.