SPRG Seminars
April 3, 2012:
"Energy transfer via Ultra Low Frequency (ULF) waves: Global perspectives from multi-spacecraft observations"
Michael Hartinger, UCLA
Ultra-Low Frequency (ULF) waves can participate in energy transfer in the near Earth space environment through a variety of different mechanisms. For example, certain ULF wave modes can accelerate electrons in the radiation belts to very high energies; these energetic electrons can in turn have a variety of negative space weather impacts, including damaging communications satellites in geosynchronous orbit. Discriminating between different ULF wave modes and determining their relative importance in energy transfer in the Earth’s magnetosphere remains an active area of research. We have used multi-point observations from the Time History of Events and Macroscale Interactions (THEMIS) mission and ground magnetometer stations to characterize the global spatial structure, time evolution, and energy transfer associated with three different ULF wave modes. In particular, we have demonstrated resonant mode coupling between the compressional and shear Alfven wave modes, we have demonstrated the existence of monochromatic global modes outside of the plasmasphere in the frequency range important for radiation belt interactions, and we have shown ion foreshock transients can be important energy source for ULF waves.