HR: 10:35h
AN: SM22B-02 INVITED     [Abstracts]
TI: Using Radially Aligned Satellites to Understand Transport and Acceleration of Energetic Particles
AU: * Reeves, G
EM: reeves@lanl.gov
AF: Los Alamos National Lab., Space Sciences Group, ISR-1 Mail Stop D-466, Los Alamos, NM 87545 United States
AB: For decades now fortuitous radial alignments of spacecraft in the magnetosphere have allowed us to study the transport of plasmas and energetic particles. Multi-spacecraft studies help resolve some of the spatial-temporal ambiguities that are inherent in single-spacecraft studies and have helped develop physical understanding that would not have been possible without simultaneous distributed measurements. Among the areas of study that have benefited from this approach is the study of the transport of energetic particles from the tail into the inner magnetosphere. The dynamics of energetic particles in the two regions are dramatically different. In the tail the drift paths are open, intersecting the magnetopause on the flanks or day side. Transport processes that act on those populations must be fast compared to the drift period in order to be effective. In contrast, the drift paths in the inner magnetosphere (for high enough energies) are closed allowing for the conservation of all three adiabatic invariants and the gradual effects of processes such as diffusion and wave-particle interactions which act over many drift periods. The inward radial transport of energetic particles from a "seed" population in the plasma sheet to the trapped or quasi-trapped populations of the inner magnetosphere and the energization that takes place as a result are crucial magnetospheric processes that have been illuminated by radially-aligned spacecraft measurements. Important examples are the transport and energization that produce the storm time ring current from plasma sheet ions and the less well-understood processes that transport and energize electrons to create the outer electron belt. In both cases however, a critical step is the action of non-adiabatic processes that "inject" electrons and ions to low L-shells and subsequently trap all or a portion of that population. Those processes include, at a minimum, substorm injections, storm-time electric field reconfiguration, and the action of waves on energetic particle populations. This talk will review examples of multi-spacecraft studies that have used radial alignments to investigate and characterize storm and substorm dynamics. It will also discuss areas where new missions such as THEMIS and LWS Geospace, that are designed for frequent radial alignments, can bring closure to some of the remaining outstanding scientific questions.
DE: 2720 Energetic particles, trapped
DE: 2730 Magnetosphere--inner
DE: 2764 Plasma sheet
DE: 2778 Ring current
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting