IGPP Seminar Series

Testing chorus generation in the radiation belts and testing auroral generators in the magnetotail

by Dr. Chris Cully
Swedish Institute of Space Physics, Uppsala, Sweden

Abstract

In Earth's dawnside magnetosphere, whistler-mode waves both accelerate and scatter the electrons that make up the radiation belts. Often, the whistler wave spectrum exhibits a characteristic rising tone; such waves are known as chorus. The physical mechanism that generates these rising-tone whistlers is not understood. One theoretical explanation, put forward by Omura et al, involves wave growth by nonlinear trapping. This theory makes some very specific and nontrivial testable predictions. In the first half of this talk, I'll discuss those predictions, and compare to satellite data from Themis, showing good agreement. An unrelated process in the magnetotail provides electric fields and field aligned currents to drive stable auroral arcs. In the second half of the talk, I'll discuss possible drivers for stable electron arcs in the night-side auroral oval, and show intervals when a plausible magnetospheric driver can be identified in combined ground- and space-based Themis data. One such interval occurs during the transition from quiet to disturbed (substorm) conditions. The resulting onset arc is driven by Hall electric fields associated with thin current sheets in the magnetotail, similar to a theoretical description by Schindler and Birn [2002].
Thursday, 08 October 2009
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM