Eighth European Space Weather Week
November 28 - December 02, 2011 - Namur, Belgium

Session 4B
Space Weather Effects on the Earth's Thermosphere, Ionosphere and Plasmasphere

Session: Session 4B: Space Weather Effects on the Earth's Thermosphere, Ionosphere and Plasmasphere (06)
Date: Thursday, December 01, 2011
Time: 09:00 - 12:30
Chair: Michael Danielides & Ioanna Tsagouri
Remarks: Introduction: 09:00-09:05
Splinter Wrap-up: 10:15-10:30
Coffee Break & Poster Session: 10:30-11:15
Summary and Close: 12:25-12:30

Seq   Time   Title   Abs No
                    09:00                               Introduction

1   09:05   >From ionospheric Climate to ionospheric Weather Modeling: the new Path
Radicella, Sandro M.

A brief introduction about the different types of ionospheric models is given describing their advantages and limitations. The evolution from a "climate description" to a "weather specification" of the ionosphere is discussed particularly in relation to Space Weather. Different ways to go from ionospheric "climate" to ionospheric "weather" based on the assimilation or ingestion of various types of data is described. Recent results will be illustrated that show the advances reached using this approach.

2   09:25   EOF Analysis applied to Australian Regional Ionospheric total Electron Content,based on GPS Observations and SCHA
Bouya, Zahra1; Terkildsen, Mike2; Francis, Matthew2
1Bureau of Meteorology, AUSTRALIA;
2Bureau of Meteorology, IPS Radio and Space Services, AUSTRALIA

This paper describes the application of Empirical Orthogonal Function (EOF) analysis to characterise spatial and temporal variation in Australian regional ionospheric Total Electron Content (TEC).
TEC data at evenly distributed grid points was estimated using the Spherical Cap Harmonic Analysis (SCHA) method, applied to GPS data collected from the Australian Regional GPS Network (ARGN). This approach yields more detailed maps of regional TEC variation than can be obtained using global models.
TEC datasets representing a range of periods were studied. EOF analysis was used to decompose each TEC dataset into a series of orthogonal Eigenfunction (EOF base function) and associated coefficients. The base function represents the variation in TEC with latitude and longitude. The coefficients represent the variation with time.
The results reveal that the first few EOFs explain the majority of TEC variability that relates to physical processes. In addition, the EOF coefficients have remarkable diurnal and longer-term periodic characteristics. In the datasets studied, the first four EOFs explain more than 95% of the TEC variation indicating effective data compression and clear separation of different physical process. EOF analysis can thus be employed to extract the main spatial variation as well as diurnal and climatic variation in TEC which can be used to build empirical model for further study.

Keywords: EOF, Regional, SCHA, GPS, Australia .

3   09:40   Upgrading the Semi-Empirical Drag Temperature Model (DTM) in the Framework of the FP7 Project ATMOP
Bruinsma, Sean

Atmospheric density models are used in satellite orbit determination and prediction programs to compute the atmospheric drag force, as well as in upper atmosphere studies. They represent temperature and (partial) density as a function of altitude, latitude, local solar time, day-of-year, and parameters related to the state of atmospheric heating due to solar EUV emissions and solar wind. The S10.7 index was selected after a thorough analysis to represent the heating by EUV, whereas new geomagnetic activity indices are being constructed and tested within ATMOP. These indices have a higher temporal resolution than Ap/Kp, namely 15 minutes instead of 3 hours.
The new model will, as a first, assimilate the full CHAMP high-resolution density data set, as well as the GRACE density data up to at least the same date (September 2010). GOCE density data, at 255 km altitude, will be assimilated as soon as they will be available. For the altitude range 120-200 km, i.e. for which data are sparse, we will try to constrain the model by means of pseudo-data coming from the first-principles model CMAT2. A new feature of the model will be that the variability in the calculated density for sub-model resolution (scales less than 3000 km approximately) will be estimated, based on analysis of filtered observed density variations.
The new DTM must predict density with the smallest bias at the scale of an orbital revolution achievable; this mean, or climatology, model will then be adapted for near-real time data assimilation in view of the required nowcast and forecast capabilities of the future European SSA system.

4   10:00   Modelling a higher Time Resolution Proxy for Geomagnetic Activity
Aylward, Alan1; Spain, Timothy2; Lathuillere, Chantal3; Menville, Michel4
1University College London, UNITED KINGDOM;
3Institut de PlanŽtologie et d'Astrophysique de Grenoble, FRANCE;
4Latmos, Guyancourt, FRANCE

Previous work with the University College London CTIP (Coupled Thermosphere Ionosphere and Plasmasphere) model has shown that time varying input of geomagnetic forcing produces wave activity in the thermosphere and affects the dynamics of the neutral atmosphere down to the equator and beyond.
That work was restricted to using the "standard" Kp planetary index which changes every 3 hours. However, under the auspices of the EU-funded ATMOP programme we have been looking at what additional effects we might see on density and temperatures if the variability of the geomagnetic activity had a more realistic time variation - that is if it were allowed to vary faster than the standard Kp allows.
The UCL CMAT2 model - a development of CTIP - has been modified to allow for virtually any scale of time variation of both F10.7 flux and geomagnetic energy to be considered, and in some first tests of the new system we have input a time varying faux-Kp proxy set with a time resolution of 15 minutes to compare to the standard 3-hour indices.
The high-resolution proxies were produced to study a recent storm period in May 2003 for which CHAMP satellite data are available for comparison to the model runs.
The new proxy is seen to produce significantly more variability in the thermosphere, especially near the auroral zone as might be expected - but the effects are seen to propagate to affect more or less the whole globe and modify the "slow-variability" picture considerably.

5   11:15   On Progress with the AMISR System - A Unique Phased ISR
Semeter, Joshua
Boston University, UNITED STATES

The Advanced Modular Incoherent Scatter Radar (AMISR) is a modular, transportable, ISR funded by the National Science Foundation. The combination of electronic beam steering, remote operation, and distributed power provides an unprecedented degree of flexibility in experiment design. For instance, pulse-by-pulse steering means that information can be accumulated simultaneously from a dense grid of beams, enabling the construction of three-dimensional images of densities, temperatures, and flows in the ionosphere. The AMISR installations can also be diverted periodically to some standard configuration without impacting other planned experiments. Such a "low duty cycle" mode was run during the entire IPY, providing zenith profiles of the ionospheric state at 10 min intervals for the entire year. In this talk I will review significant science results from the first 5 years of the AMISR project, and discuss the potential of the emerging global AMISR network as a bonafide space weather diagnostic.

6   11:35   EISCAT-3D: a versatile ground-based Instrument for Space Weather Monitoring
Grydeland , Tom

In the future, EISCAT will build the next generation incoherent scatter radar, which will provide comprehensive 3D monitoring of the atmosphere and ionosphere above Northern Fenno-Scandinavia. The EISCAT_3D radar system will consist of multiple phased arrays, using the latest digital signal processing to achieve ten times higher temporal and spatial resolution than the present radars.

The European Strategy Forum on Research Infrastructures (ESFRI) selected EISCAT_3D for the Roadmap 2008 for Large-Scale European Research Infrastructures for the next 20-30 years. The facility will be built as a modular system with the construction start by 2015.

EISCAT_3D will be a volumetric radar capable of imaging an extended spatial area with simultaneous full-vector drift velocities, having continuous operation modes, short baseline interferometry capability for imaging sub-beamwidth scales, real-time data access for applications and extensive data archiving facilities.

The design of the antenna arrays will be modular at different scales allowing for mass-production of the components. Some arrays will be very large, in the scale of tens of thousands of individual antenna elements. The receiver arrays will be located at 50-150 km distance from the illuminators, and some smaller arrays closer by to support continuous interferometric observations. The total system will comprise ?100,000 elements. The actual radar sites have to be carefully chosen.

This new large-scale European research infrastructure has applications in a wide range of European research areas including Space Weather monitoring and technology solutions supporting sustainable development, well beyond atmospheric and space sciences.

7   11:55   Calibrated Polarization Parameters of the Auroral red Line in Hornsund
Lilensten, Jean1; Barthélémy, Mathieu2; Amblard, Pierre-Olivier3; Moen, Joran4; Rothkaehl, Hanna5; Simon Wedlund, Cyril6; Lamy, Hervé6
3Gipsa Lab, FRANCE;
5Polish Space Research Center, POLAND;

The thermospheric atomic oxygen red line is one of the brigthest in the auroral spectrum. It has been shown to be polarized. This polarization depends on the auroral activity. The first measurements were performed in polar conditions with a possible contribution of light pollution. In the winter 2010 / 2011, it has been measured for the first time in totally clean conditions at the Polish Hornsund polar base. About 200 hours are fully useable. In this paper, we report on these measurements. We give for the first time calibrated values of the polarization degree, which is of the order of 2 to 3% in average. Its behaviour is confirmed : the polarization decreases when the auroral activity increases. However, the anticorrelation is not one to one, revealing a much more complex mechanism. The angle of polarization varies also with the auroral activity, rotating around the magnetic field line. This set of observations is a new step on the stairs to understand the thermospheric emission polarizations and make it an useable proxy for future space weather purposes.

8   12:10   Wave Aspects and Signatures in the Magnetosphere-Ionosphere Coupling during active geomagnetic Conditions
Voitenko, Yuriy; De Keyser, Johan
Belgian Institute for Space Aeronomy, BELGIUM

We discuss waves, their signatures, and their role in the processes coupling the Earth's magnetosphere and ionosphere in auroral zones. Simultaneous observations of enhanced wave fluxes and strong particle energization during active geomagnetic periods point on causal links between waves and energetic particles. Wave activity is mostly Alfvénic, intrinsically multi-scale, and often exhibits power-law spectral distributions indicating developed turbulence. Particle energization is anisotropic, with essentially different anisotropies for electrons and ions. We show that these observational facts can be explained quantitatively in the framework of modern theory for oblique Alfvén waves. New theoretical findings and their consequences are discussed in the context of space weather research.