Generation of Broadband Noise in the Magnetotail,
AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
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We have evaluated the generation of electrostatic noise in the geomagnetic tail by ion beams. We assume a stationary plasma-sheet electron distribution and streaming ion distributions. Both warm ion streams, as observed within the plasma sheet boundary layer, and cold ion streams, as expected from upward flowing ionospheric ions, are considered. Warm ion streams by themselves are found to be stable, whereas a cold ion stream by itself is unstable to the beam acoustic model. However, wave growth is increased if both cold and warm streams are simultaneously present. These results suggest that the interaction between the warm and cold ion streams is responsible for the peak in electrostatic wave intensities observed within the plasma sheet boundary layer. For cold and warm ions streaming in the same direction, we find wave growth peaks for wave normal angles theta O deg and wave frequencies about 0.1 x the electron plasma frequency. However, for anti-parallel streaming cold and warm ions, wave growth peaks near theta approx. 90 deg and wave frequencies are an order of magnitude smaller. Including counter streaming warm ions in addition to a cold ion stream results in wave growth that is a superposition of that for the above two cases.
- Atmospheric Physics
- Plasma Physics and Magnetohydrodynamics