HR: 0800h
AN: SH21A-0399    [Abstracts]
TI: Characterization of 90 degree depletions in solar wind suprathermal electrons as a function of radial distance and latitude using Ulysses/SWOOPS observations
AU: * Skoug, R M
EM: rskoug@lanl.gov
AF: Los Alamos National Laboratory, Space and Atmospheric Sciences, ISR-1, MS D466, Los Alamos, NM 87545 United States
AU: Gosling, J T
EM: jgosling@lanl.gov
AF: Los Alamos National Laboratory, Space and Atmospheric Sciences, ISR-1, MS D466, Los Alamos, NM 87545 United States
AU: Steinberg, J T
EM: jsteinberg@lanl.gov
AF: Los Alamos National Laboratory, Space and Atmospheric Sciences, ISR-1, MS D466, Los Alamos, NM 87545 United States
AU: McComas, D J
EM: dmccomas@swri.edu
AF: Southwest Research Institute, Space Science and Engineering Division, San Antonio, TX 78228 United States
AB: Suprathermal electron distributions observed in the solar wind by ACE/SWEPAM often show depletions centered on and symmetric about 90 degree pitch angle. It has been suggested that these distributions arise from a combination of focusing and mirroring associated with magnetic connection to magnetic field enhancements beyond the spacecraft. Observations from Ulysses/SWOOPS show that the occurrence of depletions is a function of both latitude and radial distance. During Ulysses' first orbit, near solar minimum, depletions were observed up to the highest latitudes covered by Ulysses, including latitudes where the solar wind flow was quite uniform and corotating interaction region (CIR) shocks were not observed. This suggests that high latitude magnetic field lines may connect to CIR shocks at lower latitudes. Alternatively, it is possible that fluctuations in field magnitude could produce the observed depletions, since the magnetic field enhancements required to produce the observed depletions are relatively weak (approximately a factor of 1.1-1.5). We characterize the occurrence and properties of depletions observed by Ulysses as a function of latitude, radial distance, and solar cycle, and consider possible mechanisms for the formation of these electron distributions.
DE: 7807 Charged particle motion and acceleration
DE: 2134 Interplanetary magnetic fields
DE: 2162 Solar cycle variations (7536)
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting