SM31E-01 INVITED 

Geosynchronous Proton Fluxes as a Pointer of Global Proton Distribution in the Inner Magnetosphere

* Milillo, A (anna.milillo@ifsi-roma.inaf.it), INAF/IFSI, via del Fosso del Cavaliere 100, Rome, 00185, Italy Orsini, S (stefano.orsini@ifsi-roma.inaf.it), INAF/IFSI, via del Fosso del Cavaliere 100, Rome, 00185, Italy Marcucci, M F (federica.marcucci@ifsi-roma.inaf.it), INAF/IFSI, via del Fosso del Cavaliere 100, Rome, 00185, Italy

The geosynchronous orbit is the edge region where plasma sheet and ring current populations join to each other, where different current systems merge and where protons become to be trapped into closed trajectories thus having time to diffuse inward. Hence, the proton fluxes observed at this orbit have the potentiality to provide information about the neighboring regions. In fact, by using the proton fluxes at the geosynchronous orbit, it has been possible to reconstruct through an empirical approach the global evolving proton distributions in the inner magnetosphere. In this presentation some applications of the LANL data to the Milillo et al. (2001) model are reviewed. In particular, we highlight that by this approach it is possible to derive the evolving characteristics of the convected population and the relative contribution of the tail and the ring currents during geomagnetic storms and to study the effect of dual lobe reconnection in the inner magnetosphere.

SM31E-02 

New Measurements of Plasma Ion Composition at Geosynchronous Orbit

* MacDonald, E A (macdonald@lanl.gov), Space Science and Applications, MS D466 Los Alamos National Laboratory, Los Alamos, NM 87545, United States Funsten, H O (hfunsten@lanl.gov), Space Science and Applications, MS D466 Los Alamos National Laboratory, Los Alamos, NM 87545, United States Thomsen, M F (mthomsen@lanl.gov), Space Science and Applications, MS D466 Los Alamos National Laboratory, Los Alamos, NM 87545, United States Dors, E E (edors@lanl.gov), Space Science and Applications, MS D466 Los Alamos National Laboratory, Los Alamos, NM 87545, United States Jordanova, V K (vania@lanl.gov), Space Science and Applications, MS D466 Los Alamos National Laboratory, Los Alamos, NM 87545, United States

Next generation plasma spectrometer data with ion composition capability will be available on government satellites at geosynchronous orbit beginning in 2007. This capability has not been fielded directly at geosynchronous orbit in over 20 years. We anticipate significant gains in understanding the role of heavy ionospheric ions, their energization, and their transport through the magnetosphere. Oxygen can dominate the composition of the plasma sheet and ring current during the largest geomagnetic storms, and thus is important to monitor and understand. In addition, this new capability will enable more accurate ring current modeling, of critical importance to space weather applications. Initial observations will be presented along with assessment of the new ion composition measurement technique utilized in the limited resource plasma spectrometer.

SM31E-03 INVITED 

Testing the necessity of transient spikes in the drivers for creating a storm-time ring current

* Liemohn, M W (liemohn@umich.edu), University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States Ilie, R (rilie@umich.edu), University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States Ridley, A J (ridley@umich.edu), University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States Kozyra, J U (jukozyra@umich.edu), University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States Thomsen, M F (mthomsen@lanl.gov), Los Alamos National Laboratory, ISR-1, MS D466, Los Alamos, NM 87545, United States Borovsky, J E (jborovsky@lanl.gov), Los Alamos National Laboratory, ISR-1, MS D466, Los Alamos, NM 87545, United States

The role of transient spikes in upstream solar wind parameters and near-Earth plasma sheet parameters is investigated through a series of numerical simulations. During magnetic storms, the near-Earth plasma sheet density (as observed at geosynchronous altitude) is often enhanced relative to its normal, quiescent level. In addition to a baseline increase of the density of up to a few per cubic centimeter lasting several hours, there are usually short-lived (a few to tens of minutes) increases on top of this (up to double the baseline). In addition, the solar wind parameters also often have numerous short-lived spikes and fluctuations within it. The question then arises of the relative contribution of these transient spikes in the drivers to the storm-time ring current intensity. To address this issue, a series of simulations are conducted using the Hot Electron and Ion Drift Integrator (HEIDI) model (formerly the Michigan version of RAM). Various running averages of the upstream solar wind conditions and geosynchronous orbit nightside boundary conditions are used to drive HEIDI. It is found that the spikes are simply adding a linear contribution to the ring current intensity over the baseline (averaged) input levels, and that any nonlinear influences occur beyond the HEIDI simulation domain (i.e., at high latitudes or in the tail). That is, the spikes do not last long enough to develop nonlinear influences on the ring current's total energy content. The HEIDI results are compared against global magnetospheric modeling results using averaged input parameters into the Space Weather Modeling Framework (SWMF), which show a nonlinear response to transient spikes.

SM31E-04 

Self-excited unstable behavior of the ring current in the vicinity of the geosynchronous orbit

* Ebihara, Y (ebihara@stelab.nagoya-u.ac.jp), Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464- 8601, Japan Fok, M (mei-ching.fok@gsfc.nasa.gov), NASA GSFC, Code 673, Greenbelt, MD 20771, United States

It has been suggested that the outer ring current is unstable to the interchange-like instability when the earthward pressure gradient is steep enough. Such a condition can be achieved from a sudden decrease in the plasma sheet density. Here we show from computational results that the interchange-like instability can occur without changing the plasma sheet density. We solved a bounce-averaged drift kinetic equation with the electric field calculated based on conservation of electric currents flowing between the magnetosphere and the ionosphere. The magnetic field in the inner magnetosphere was calculated based on requirement of the force balance between the plasma pressure and the magnetic field by using the Biot-Savart law. At the beginning of the simulation, the convection electric field was enhanced to the condition corresponding to IMF Bz=-20 nT, and kept constant in time throughout the simulation. In the early stage of the simulation, the equatorial magnetic field became highly inflated around L=5. The perpendicular plasma pressure decreases due to adiabatic cooling. The anisotropy of the plasma pressure enlarged the westward current, which further enhances in the inflation of the equatorial magnetic field. Consequently, the earthward pressure gradient became steep, and the interchange- like instability occurred spontaneously. This self-excited instability vanished when the inner edge of the plasma sheet moves to the inner region where the magnetic pressure is high in comparison with the plasma pressure. Our results imply that, in some cases, the development of the ring current does not proceed smoothly in its early stage even though the plasma sheet parameters are constant in time.

SM31E-05 

Trans-geosynchronous Characteristics of Plasma and Energetic Particles Using SCATHA Data

* Fennell, J F (joseph.fennell@aero.org), The Aerospace Corporation, MS:260 POBox 92957, Los Angeles, CA 90009-2957, United States Roeder, J L), The Aerospace Corporation, MS:260 POBox 92957, Los Angeles, CA 90009-2957, United States

The SCATHA satellite made several years of detailed plasma, energetic particle and magnetic field observations over geocentric radial distances of 5.5 to 7.5. Thus SCATHA provides the capability to characterize the particle environment both external and internal to geosynchronous orbit. This allows one to infer relationships between parameters such as the characteristic energy of electrons and ions and the hot plasma density as functions of radial distances, that span geosynchronous, local time and magnetic conditions. One minute summary SCATHA plasma and energetic particle data were used to calculate the average energies for the electrons and protons and the hot plasma density and perpendicular pressure. For example, over a selected interval in the night side magnetosphere (post dusk to pre dawn) the average energy of the hot plasma protons (150 eV to 133 keV) decreases with increasing L (5.5<L<7) such that it is nearly twice as high at L=5.5 (23 keV) as it is at L=7 (12 keV), consistent with expected cross field energy gain from convection. At the same time the average (and mean) electron energy increased slightly with increasing L from 1.9 keV at L=5.5 to 2.2 keV at L=7. However the relative scatter in the electron average energy values was quite large. SCATHA also provides the phase space density (PSD) of energetic electrons over a wide range of first and second invariants. This allows one to assess the gradients in PSD with radial distance both near and off the magnetic equator. For example, during one moderate storm in April 1986 the PSD was observed to be monatomic near the magnetic equator while it show a peak near L*=5.5 Re well off the equator. These and other results will be shown and discussed in the context of what they show about the character of the energetic plasmas in radial regions that traverse geosynchronous orbit.

SM31E-06 INVITED 

Radial Transport of Radiation Belt Electrons in the Vicinity of Geosynchronous Orbit

* Ukhorskiy, A (ukhorskiy@jhuapl.edu), JHU/APL, Applied Physics Laboratory 11100 Johns Hopkins Rd, Laurel, MD 20723, United States Sitnov, M (sitnov@jhuapl.edu), JHU/APL, Applied Physics Laboratory 11100 Johns Hopkins Rd, Laurel, MD 20723, United States

Earth's outer radiation belt is populated by relativistic electrons that produce a complex dynamical response to varying geomagnetic activity. One fundamental process defining global state of the belt is radial transport of electrons across their drift shells. Radial transport is induced by resonant interaction of electron drift motion with ULF oscillations of electric and magnetic fields and is commonly believed to be a diffusive process. The goal of this paper is the analysis of radial transport due to typical ULF fluctuations in the inner magnetospheric fields. For this purpose a test-particle approach is used in the guiding center approximation. In particular we consider ULF oscillations due to global magnetospheric compressions. It is shown that typical variations in the pressure induce large-scale fluctuations in magnetic and inductive electric fields that produce a substantial impact on relativistic electrons. We show that electron transport in these fields and presumably in the fields due to other ULF mechanisms including field line resonances and magnetosonic waves is controlled by the amplitudes of field fluctuations and their spectral properties. Electron motion becomes stochastic due to overlap of electron populations trapped in the vicinities of drift resonances with adjacent harmonics of the field spectrum. It is shown, however, that in spite of the underlying stochasticity the radial diffusion limit is not fully attainable in the outer radiation belt. This is attributed to the fact that phase correlations in electron motion do not have time to decay due to finite size of the system. As a result collective motion of the outer belt electrons can exhibit large deviations from radial diffusion. Solution of the full Liouville's equation is required for accurate description of radial transport in the belt.

SM31E-07 

Polar Spacecraft Observations of Intense Wave Electric Fields in the Inner Magnetosphere

* Wygant, J R (jwygant@ham.space.umn.edu), School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States Mozer, F (Fmozer@ssl.berkeley.edu), Space Science Laboratory, University of California, Berkeley, CA 94720, United States Blake, J B (jBernard.Blake@aerospace.org), Space Science Department, Aerospace Corporation, Los Angeles, CA 90009, United States Scudder, J (jack-scudder@uiowa.edu), Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, United States Pickett, J (jolene-pickett@uiowa.edu), Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, United States Russell, C T (ctrussell@igpp.ucla.edu), I.G.P.P., University of California, Los Angeles, CA 90009, United States Cattell, C A (cattell@belka.space.umn.edu), School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States Dombeck, J (johnd@fields.space.umn.edu), School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States Lei, D (ldai@fields.space.umn.edu), School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States

This talk presents recent observations in the inner magnetosphere of extremely intense lower hybrid electric field structures/waves with amplitudes ranging up to 700 mV/m over the frequency range from 50-300 Hz using burst data from the Berkeley Electric Field Instrument (EFI) on the Polar spacecraft. These are among the most intense waves ever observed in the inner magnetosphere near and within the outer electron radiation belts. The waves were observed on the night-side near the equatorial plane(<30 degrees) at 4>c) dominated by the longitudinal component of the electric field. The wave fields are often found at the edges of order of magnitude density gradients and are associated with electron thermal flux fluctuations that are on the order of 30% of the estimated background electron density. The burst electric field data also provides evidence for 50-100 mV/m discrete bipolar solitary electric field structures directed parallel to the ambient magnetic field with durations on the order of ~ 1 ms imbedded in the large amplitude turbulence. The relation of these waves and structures to quasi-static electric fields associated with substorms, Alfven waves, the PSBL, and the acceleration of energetic electrons and ions will be discussed.

SM31E-08 INVITED 

Deformation methods in modelling of the inner magnetospheric electromagnetic fields

* Toivanen, P K (petri.toivanen@fmi.fi), Finnish Meteorological Institute, Erik Palmenin Aukio 1, Helsinki, 00560, Finland

Various deformation methods have been widely used in animation image processing. In common terms, they are mathematical presentations of deformations of an image drawn on an elastic material under stretching or compression of the material. Such a method has also been used in modelling of the magnetospheric magnetic fields, and recently been generalized to include also the electric fields. In this presentations, the theory of the deformation method and an application in a form of a new global magnetospheric electromagnetic field model are previewed. The main focus of the presentation is on the inner magnetospheric current systems and associated electromagnetic fields during quiet and disturbed periods. Finally, a short look at the modern deformation methods in image processing is taken. These methods include the Free Form Deformations and Moving Least Squares Deformations, and their future applications in magnetospheric field modelling are discussed.

Author(s) (2007), Title, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract #####-##.