SM22B-01 10:20h
Electrodynamic coupling of fast flows to the high latitude ionosphere as evidenced by Cluster-Polar correlations.
We present a series of Cluster (at ~19 Re) and Polar (at ~9 Re) magnetotail alignments when large activity was observed in the plasma sheet on at least one of the two locations. We present the energy flux available in Alfven waves and examine the dissipation of that energy in the region between Cluster and Polar. We comment on the implications of our findings for the inward evolution of the flows and for plasma heating.
SM22B-02 INVITED 10:35h
Using Radially Aligned Satellites to Understand Transport and Acceleration of Energetic Particles
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.
SM22B-03 10:50h
CLUSTER measurements of energetic electron bursts in the context of global multispacecraft observations: The telescope-microscope combination
The space research community has long sought the capability to view the Sun-Earth system in a global way and concurrently to probe the microphysical details of key physical regions. This objective has now been substantially realized with the use of the CLUSTER and IMAGE missions in combination with ACE, FAST, POLAR, and geostationary orbit spacecraft. Using such multispacecraft data with appropriate radial positioning, there is a powerful ability to apply both `telescopic' and `microscopic' principles. Many recent examples from the 2001, 2002 and 2003 CLUSTER tail seasons serve to illustrate the observational power of these new tools. In the case of the 31 March 2001 superstorm, we observed a strong geomagnetic storm and saw a powerful compression of the magnetosphere and a concomitant particle injection event. In another event on 27 August 2001, CLUSTER observed a clear substorm sequence of events in the mid-magnetotail region (X~-19RE) while the other spacecraft in the constellation saw the near-Earth substorm consequences. In these examples, CLUSTER data revealed microphysical details while IMAGE and other spacecraft showed the global, macroscopic substorm context. We present in this paper our analyses of several substorm events (analogous to the 27 August 2001 case) in order to understand the radial propagation of substorm expansion phase processes.
SM22B-04 11:05h
Multiplatform Investigation of the Role of Wave Accelerated Electrons in Magnetospheric Processes
Intense fluxes of wave accelerated low energy electrons in auroras signify the location of large scale energy input from the magnetosphere. Studying these wave accelerated electron (WAE) auroras require the monitoring of the auroral dynamics by high resolution (ground- or space-based) imaging while simultaneously measuring the particles at various altitudes to determine the characteristic electron spectrum and to observe the transition of wave Poynting flux into electron energy. This wave acceleration is another distinct and presumably transient process by which magnetic energy of the magnetosphere is converted into particle (electron) energy and transmitted into the atmosphere in the form of auroral electrons. Using the FAST satellite and auroral imaging from the IMAGE spacecraft we were able to show that prior to substorm onset WAE auroras occur infrequently and mostly near the poleward boundary of the auroral oval, presumably near the boundary of open and closed field lines, where steady state reconnection is expected to occur. At onset WAE electrons play a primary role in the surge formation and the break up aurora. This aurora is located deep in the region of closed field lines. After onset the poleward propagating auroral surge consists of WAE electrons at the poleward edge of the closed field configuration and is closely followed by inverted V type precipitation. The ground based auroral imaging operating simultaneously with the future THEMIS satellites will have better spatial resolution for the investigation of the aurora associated with these processes.
SM22B-05 INVITED 11:20h
Global evolution of the high energy magnetospheric electron population during substorms.
The substorm phenomenology of the magnetospheric high energy electron population has been thoroughly studied with geosynchronous particle observations. We have a much less developed understanding of the radial extent and evolution of, for example, substorm injections. Riometer absorption has been shown to be a good proxy for the integrated high energy electron flux near the equatorial plane, provided specific conditions are met [Baker et al., JGR, 86, 2295, 1981]. In recent work, we are attempting to map out, in advance of NASA's upcoming Time History of Events and Mesoscale Interactions During Substorms (THEMIS) project, the capabilities and limitations of the three techniques we now have (ie., X-ray imaging, riometers, and in situ particle observations) to characterize the mesoscale response of the high energy electron population to this most dynamic phase of the substorm. In this paper, we use data from a latitudinally distributed array of riometers in conjunction with in situ particle data and global X-ray images to explore the L-value dependence of the evolution of the high energy electron population during the substorm expansive phase.