The dynamics of the high energy electron radiation belt is of central importance to space weather and a topic of intense scientific interest, highlighted by the recently launched Val Allen Mission's Radiation Belt Storm Probes (RBSP). While significant progress has been made in understanding the underlying physical processes (radial diffusion, wave particle interactions) our ability to accurately model these dynamics is still limited by our insufficient knowledge of critical model inputs and boundary conditions. In this talk we will concentrate on the role the cold plasma density in controlling these dynamics, highlighting the the need for accurate, global cold plasma density models as a pre-requisite for high fidelity space weather modeling and prediction. In addition we will present the state of data resources from the RBSP satellites for cold plasm density measurements.

The plasmasphere is often regarded as a reasonably uniform region of dense, co-rotating cold plasma, but in fact is a dynamic environment varying over a range of time and distance scales and populated by both low and high energy particles. Some of the most important space weather processes involve wave-particle interactions, but wave properties may also be used to remote sense plasmasphere dynamics. Since satellites move rapidly at low altitudes such remote sensing efforts can provide significant contributions to the development of plasmasphere models. This presentation will outline some key remote sensing techniques based on ULF and VLF wave measurements, and will present examples of space weather applications. While ground-based magnetometers are often the platform of choice for ULF wave measurements, HF radars offer many advantages, some of which will also be illustrated.

The Automatic Whistler Detector and Analyzer Network (AWDANet) is able to detect and analyze whistlers in quasi-realtime and can provide equatorial electron density data. The plasmaspheric electron densities and ionosphere-plasmasphere coupling fluxes are key parameters for plasmasphere models in Space Weather related investigations, particularly in modeling charged particle accelerations and losses in Radiation Belts. The global AWDANet [1] detects millions of whistlers in a year. The system has been recently completed with automatic analyzer capability in PLASMON (http://plasmon.elte.hu) project. It is based on a recently developed whistler inversion model [2], that opened the way for an automated process of whistler analysis, not only for single whistler events but for complex analysis of multiple-path propagation whistler groups [3]. In this paper we present the first results of quasi-real-time runs processing whistlers from quiet and disturb periods. Refilling rates, that are not yet known in details are also presented for the various periods.

[1] Lichtenberger, J., C. Ferencz, L. Bodnár, D. Hamar, and P. Steinbach (2008), Automatic whistler detector and analyzer system: Automatic whistler detector, J. Geophys. Res., 113, A12201, doi:10.1029/2008JA013467.

[2] Lichtenberger, J. (2009), A new whistler inversion method, J. Geophys. Res., 114, A07222, doi:10.1029/2008JA013799.

[3] Lichtenberger, J., C. Ferencz, D. Hamar, P. Steinbach, C. J. Rodger, M. A. Clilverd, and A. B. Collier (2010), Automatic Whistler Detector and Analyzer system: Implementation of the analyzer algorithm, J. Geophys. Res., 115, A12214, doi:10.1029/2010JA015931.

The technique for remote sensing the plasma mass density in magnetosphere by geomagnetic field line resonances detected at ground-based stations is getting more and more popular after the establishment in the last few years of extended magnetometer arrays, such as the EMMA network recently formed in the framework of the EU FP-7 PLASMON project. It is important therefore to quantify the level of accuracy associated to such technique. In this talk we examine the effect of using different magnetic field models.
First the equatorial plasma mass density estimates obtained using the dipole approximation are compared with those obtained using the IGRF model for low-mid latitudes. It is found that the use of the dipole model may result in an error in the inferred density appreciably larger than what is usually assumed. In particular it shows a significant longitudinal dependence being, for example, of the order of +30% in the american sector and -30% at the opposite meridian for field lines extending to a geocentric distance of 2 Earth radii. This may result in an erroneous interpretation of the longitudinal variation in plasmaspheric density when comparing results from ground-based arrays located at different longitudes. A simple modification of the technique is proposed which allows to keep using the dipole approximation but with a significant error reduction.
Then the results of using the T01 Tsyganenko model are compared with those based on dipole/IGRF models. With respect to previous evaluations of the differences in the inferred equatorial density we take into account the different equatorial crossing points of the IGRF and T01 field lines traced from a given ground position by considering reasonable radial gradients of the equatorial density. For average solar wind/magnetospheric conditions, mass densities computed using the IGRF model result to be moderately overestimated (less than 20%) for L values < 4. The uncertainty obviously increases for higher L values and the bias may become negative for steep radial variations of the equatorial density. For storm-time conditions the error dramatically increases beyond L ~ 4, but may remain within ~ 20% for L < 4 assuming radial variations of the equatorial density which are typical for such magnetospheric conditions.
We also present some specific case studies using measurements provided by the european magnetometer network EMMA.

A three-dimensional dynamic model of the plasmasphere has been developed using the kinetic approach to determine the number densities and temperatures of the different particle species.The plasmapause is determined by the location where field-aligned plasma interchange motion becomes convectively unstable. The position of the plasmapause in the different MLT sectors is controlled by the convection electric field combined with co-rotation. During geomagnetic storms and substorms, a plasmaspheric plume is generated.
The model has been coupled with the ionospheric model IRI. A relation between the plasmapause position and the ionospheric trough has been found in the night sector. Ionospheric densities and temperatures are used as boundary conditions for high latitude polar wind as well.
The position of the plasmapause has been compared with sub-oval aurora spots and with the radiation belts boundaries observed by different spacecraft. It is found that the plasmasphere has an influence on the dynamics of the energetic electrons in the radiation belts since the plasmapause and the radiation belt boundaries show an interesting correlation.

VLF and magnetometer observations can be used to remotely sense the plasmasphere. VLF whistler waves can be used to measure the electron density and magnetic Field Line Resonance (FLR) measurements can be used to measure the mass density. In principle it is then possible to remotely map the plasmasphere with a network of ground-based stations which are also less expensive and more permanent than satellites. The PLASMON project, funded by the EU FP-7 program, is in the process of doing just this. A large number of ground-based observations will be input into a data assimilative framework which models the plasmasphere structure and dynamics. The data assimilation framework combines the Ensemble Kalman Filter with the Dynamic Global Core Plasma Model. In this presentation we will describe the plasmasphere model, the data assimilation approach that we have taken, PLASMON data and data assimilation results for specific events.

In this study was will present a description of the PLASMON-developed model of energetic electron precipitation (EEP) fluxes inside and outside of the plasmasphere during space weather events. The aim of the PLASMON EEP model is to identify 3 or 4 MLT zones which are populated by ULF/VLF waves that can generate energetic electron precipitation. The MLT zones are influenced by the MLT-dependent plasmaspheric density structures such as the plasmapause. During geomagnetic disturbances the intensities of the ULF/VLF waves are enhanced, plasmaspheric structures are modified, and differing levels of precipitation flux are generated. The model will characterise the storm-time variations in electron precipitation relative to the plasmapause, building on the outputs of the data assimilative model of plasmasphere undertaken by the PLASMON project, and observations of EEP characteristics made by the PLASMON ground-based VLF receiver network.

Although our knowledge on the plasmasphere dynamics has improved greatly thanks to some recent space missions (IMAGE, CLUSTER), continuous monitoring of the plasmapause position remains unsolved. Ground based observation of geomagnetic field line resonances (FLRs) has the potential to achieve this goal. A meridional array of properly spaced magnetometers, such as EMMA (European quasi-Meridional Magnetometer Array set-up in frame of PLASMON EU FP7 project), can provide dayside plasma density profiles. Compared to VLF whistlers FLRs have the advantage that they are often observed not only in the plasmasphere, but also outside it, in the plasmatrough making them suitable for the detection of the plasmapause.
The detection of FLRs is based on the phase gradient observed between stations closely spaced in north-south direction. At normal conditions FLR can be identified by a maximum in the cross phase spectra. In case when the plasmapause moves over a station pair the phase difference at the resonant frequency changes its sign temporarily. This feature yields another possibility for the detection of the plasmapause.
We present some events to demonstrate how the motion of the plasmapause can be monitored by means of EMMA. Data assimilative model of the plasmasphere developed in the frame of PLASMON combines the observations and physics to provide plasmapause positions in all local time sectors. Results are compared to in situ plasma density measurements (IMAGE RPI) and various empirical models.

Energetic electron precipitation into the atmosphere acts as a loss mechanism for the outer radiation belt electron population, and as an indicator of the mechanisms taking place. Through a complex interplay between the acceleration, transport, and loss of electrons, individual geomagnetic storms can drive large changes in the flux of relativistic electrons within the outer radiation belts, potentially damaging satellites, and endangering astronauts. Subionospherically propagating very low frequency (VLF) radio waves can be used to monitor electron precipitation through changes in the ionization rate at altitudes of 50-90 km. In this study we analyse data from a VLF receiver located in Churchill, Canada, and concentrate on signals from two US VLF transmitters in order to provide some estimate of precipitating electron fluxes originating from the outer radiation belt. We show analysis from a space weather event, which induced changes in the radiation belt environment through enhancing relativistic electron fluxes, in July-August 2010. We combine the data from the two transmitters in order to confirm estimated fluxes, calculate the error bars, and inter-compare the results. The location of the plasmapause is taken into account in order to interpret the evolution of the electron precipitation characteristics throughout this space weather event.

One of the major objective in PLASMON project (http://plasmon.elte.hu) is to provide plasma densities for data assimilative modeling of plasmasphere from two ground based measurements: whistlers and field line resonances (FLRs). The whistler inversion method used in this procedure includes various model, such as wave propagation, magnetic field, field aligned density distribution and equatorial electron density models. The latter one is a special one used for multiple-path whistler groups. In this paper we will present the effect of various models used in the inversion procedure.
As one can obtain electron densities from whistler inversion and plasma mass densities from FLRs, the ion constitution would be required to connect the to data set (that are intended to use in the plasmasphere model), which is rarely known or available. Therefore we have developed a method for cross calibration of the data from the two sources. It includes physics based and experimental field aligned plasma density distribution models as well as comparison with in situ wave and density (IMAGE, Cluster and Van Allen Probes) measurements.

Nowadays GPS TEC (total electron content) is one of the mostly used parameter in the ionosphere's investigation. In fact, the TEC value can be considered as the combined contribution of the ionosphere and overlying plasmasphere. However one of the main limitations of the GPS technique is that the value of GPS TEC has an integral character and it is difficult to determine the contribution of the ionosphere/plasmasphere regions to GPS TEC based on ground-based GPS measurements only.

In the given report we used the International Reference Ionosphere Extended to Plasmasphere (IRI-Plas) model (Gulyaeva et al., 2002) to obtain model-derived estimates of plasmaspheric and ionospheric TEC. IRI-Plas was developed within the framework of Project WD 16457 of International Standardization Organization, ISO. One of the main advantages of IRI-Plas that it has the plasmasphere extension and is able to provide electron density profiles and total electron content at altitudes of 80 to 35,000 km for any location of the Earth. To make comparison with Jason-1 data possible, some changes in the default parameters were done: the ionosphere was considered within altitudes' limits of 100-1,336 km, plasmasphere – from 1,336 km (Jason-1 orbit) up to 20,000 km (GPS orbit). IRI-Plas results were retrieved for different seasons and different solar activity conditions. Main peculiarities of the IRI-Plas-derived ionosphere/plasmasphere electron content variability for solar minimum and solar maximum conditions are discussed; obtained results were compared with Jason-1 observations, reported in (Lee et al., 2013).

References.

Lee H.-B., Jee G., Kim Y.H., Shim J.S.. Characteristics of global plasmaspheric TEC in comparison with the ionosphere simultaneously observed by Jason-1 satellite.
Journal of Geophysical Research: Space Physics, V. 118, 1-12, doi:10.1002/jgra.50130, 2013

Gulyaeva T.L., Huang X., Reinisch B.. Ionosphere-Plasmasphere Model Software for ISO. Acta Geod. Geoph. Hung., 37 (2-3), 143-152, 2002.

The conventional ionosondes are used to collect data of ionosphere right above the ionosonde location and to provide a picture of the ionospheric properties. Although these ionosonde stations are located worldwide, there are locations where it is not easy to operate one, like oceans, deserts and other remote places. Knowing the ionospheric properties and behaviors at these parts of the world is also very important to know. The oblique sounding technique is one method to achieve this and reach those locations.
With oblique sounding the transmitter and the receiver locations are far apart from each other, even thousands of kilometers or miles. The oblique ionospheric sounding technique have some advantages in terms of that the obliquely sounded HF signal have the abilities to monitor the ionosphere of some places where it is not deployed vertical sounder between transmitter and receiver and of course, to vertically detect the ionosphere of area where it is deployed itself. It allows obtaining more information of ionosphere, such as critical frequency, vertical height and electron density, MUF (maximum usable frequency) over a wider area with no additional ionosonde.
We present the results of experimental studies of oblique sounding for research purpose between Jeju and Icheon stations in Korea which are about 420km apart. The extraction algorithm of electron density profiles after conversion of the oblique to vertical ionogram which should be considered the incidence angle, the Doppler frequency, the influence of traveling ionospheric disturbances (TIDs), the multipath propagation, and the error probability are mainly focused in this paper. This paper is also concerned with the auto scaling of oblique sounding ionogram for analysis of propagation conditions on a fixed point-to-point measurement as a near term activity.

There are presented results of the comparative analysis of GPS TEC data and FORMOSAT-3/COSMIC radio occultation measurements during period of quiet and disturbed conditions. COSMIC-derived electron density profiles were integrated up to the height of 700 km (altitude of COSMIC satellites), the estimates of ionospheric electron content (IEC) on a global scale were retrieved with use of spherical harmonics expansion. Joint analysis of GPS TEC and COSMIC data allows us to extract and estimate electron content corresponded to the ionosphere (its bottom and topside parts) and the plasmasphere (h>700 km) for different conditions. In order to analyze seasonal behaviour of PEC contribution to GPS TEC at the different regions we selected several specific points with coordinates, corresponded to the approximate positions of different, mid-latitude and low-latitude, ionospheric sounding stations. For each specific points GPS TEC, COSMIC IEC and PEC estimates were analyzed. During solar minimum conditions percentage contribution of ECpl to GPS TEC indicates the clear dependence from the time and varies from a minimum of about 25-50% during day-time to the value of 50-75% at night-time. Contribution of both bottom-side and topside IEC has minimal values during winter season in compare with summer season (for both day- and night-time). Several case-studies of geomagnetic storms were analyzed in order to estimate changes and redistribution of electron content between ionosphere and plasmasphere. The obtained results were compared with TEC, IEC and ECpl estimates retrieved by Standard Plasmasphere-Ionosphere Model that has the plasmasphere extension up to 20,000 km (GPS orbit) .

As space weather models become more sophisticated they require increasing amounts of computing power. Additionally, as these models are used for data assimilation, the amount of computing power required is multiplied again, sometimes by several orders of magnitude, because a large ensemble of models must be run. In recent years a lot of attention has been given to computation on Graphics Processing Units (GPUs), and processor manufacturers have developed new types of GPUs which are more suitable for more general purpose computation than graphics processing alone. This class of General Purpose GPUs (GPGPUs) are being used in a wide range of computational tasks. GPGPUs have very large computational throughput. High-end GPGPUs may deliver 10 to 100 times (or more) the computational power of an equally-priced CPU workstation. However, GPUs also have limitations. The large increase in computing power comes at the cost of control-logic. The consequence of that is that many of the 1000's of cores on a GPU must perform the exact same computation simultaneously. This requires new approaches to parallelization. In this presentation we will discuss the implementation of the Dynamic Global Core Plasma Model (DGCPM) on a GPGPU and show some benchmarking results.

The mid-latitude electron density trough observed in the topside ionosphere has been shown to be the near-Earth signature of the magnetospheric plasmapause, and thus its behaviour can provide useful information about the magnetospheric dynamics, since its existence is dependent on magnetospherically induced motions. Mid-latitude trough is mainly the night-time phenomenon, which detailed characteristics and features depend on the solar cycle, season, time of the day and many others.
The trough is narrow in latitudes but extended in longitudes. The main ionospheric trough features is very dynamic structure. It is well-known fact that the trough structure moves to the lower altitudes both with increasing the level of geomagnetic activity as with increasing the time interval from the local magnetic midnight However the longitude dependence of the main ionospheric structures has been detected still the source of this physical phenomena is not well understood.
Using the DEMETER in situ satellite particle and waves measurements, GPS observations collected at IGS/EPN network, and the data retrieved from FORMOSAT-3/COSMIC radio occultation measurements the mid-latitude trough characteristics with regard to the geographic and magnetic longitude at fix local time has been presented. In this presentation, based on the selected number of geomagnetic storms, we analize also the energy deposition in areas adjacent to the structure of the main ionospheric trough. The investigation confirmed the storm-phase dependence of the trough properties.The special emphasizes has been placed on analysis of behavior main ionospheric trough region during

On www.spaceweather.eu we provide a dynamic plasmasphere model, which can be used for nowcasting and forecasting during quiet periods and during geomagnetic storms. We provide colorful plots and data files of the density and temperature of the electrons, protons and helium ions. Plasma plumes are generated during disturbed periods. This 3D model contains the ionosphere, the plasmasphere, the plasmatrough and the polar wind.

Based on CLUSTER satellite measurements, a dynamic model of the radiation belts is in development. This model forecasts particle fluxes based on the predicted Dst index. In the outer electron belt it generally shows a particle dropout during the main phase of a geomagnetic storm and a particle flux increase of several orders of magnitude after the storm.