HR: 14:25h
AN: SM43D-04    [Abstracts]
TI: Possible relationship between phase space electron holes and LF/MF whistler mode dispersive signals in the auroral ionosphere: Rocket observations and ray-tracing
AU: * LaBelle, J
EM: jlabelle@einstein.dartmouth.edu
AF: Dartmouth College, Dept of Physics Wilder Lab 6127, Hanover, NH 03755 United States
AU: Samara, M
EM: marilia@aristotle.dartmouth.edu
AF: Southwest Research Institute, Space Science Department 6220 Culebra Road, San Antonio, TX 78238-5166 United States
AB: The SIERRA sounding rocket was launched January 14, 2002, northward from Poker Flat, Alaska, to an altitude of 735 km in active aurora. On the downleg in the altitude range 500-700 km, the on-board high frequency wave experiment detected structured whistler mode signals in the frequency range 100--1000 kHz, lasting nearly 200 s during which the rocket moved approximately 200 km downrange. The most prominent feature consisted of narrowband signals with frequency descending from 500 kHz to 250 kHz in about 0.5 s, with bandwidths ~ 10 kHz, with frequency spacings ~ 25 kHz, and with amplitudes in the range 10-100 μ V/m. The structured whistler mode signals coincide with a region of Alfvenically accelerated electrons of the type often associated with variable (upward/downward) currents, poleward of the inverted-V electron structures usually associated with the upward current region. However, on short timescales there was no clear correlation between the whistler mode signals and the locally detected electron fluxes. We put forth that these signatures might arise from propagation of whistler mode waves shed from upward-moving phase space electron holes which occur at much higher altitudes in the downward current regions. Ray-tracing calculations support this hypothesis by showing that sources moving upward with the typical speed of electron holes, 1000 km/s, when ray-traced through a model ionosphere to rocket altitudes, would exhibit the the magnitude of dispersion of the observed features.
DE: 2471 Plasma waves and instabilities (2772)
DE: 2487 Wave propagation (0689, 3285, 4275, 4455, 6934)
DE: 2704 Auroral phenomena (2407)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005