HR: 1340h
AN: SH33B-0375    [Abstracts]
TI: Whistler Scattering of Suprathermal Electrons in the Solar Wind: ACE Observations
AU: Pagel, C
EM: pagel@bu.edu
AF: Center for Space Physics, Boston University, Boston, MA 02215 United States
AU: * Gary, S P
EM: pgary@lanl.gov
AF: Los Alamos National Laboratory, M.S. D466, Los Alamos, NM 87545 United States
AU: deKoning, C A
EM: dekoning@lanl.gov
AF: Los Alamos National Laboratory, M.S. D466, Los Alamos, NM 87545 United States
AU: Skoug, R M
EM: rskoug@lanl.gov
AF: Los Alamos National Laboratory, M.S. D466, Los Alamos, NM 87545 United States
AU: Steinberg, J T
EM: jsteinberg@lanl.gov
AF: Los Alamos National Laboratory, M.S. D466, Los Alamos, NM 87545 United States
AB: Suprathermal electrons in the solar wind have a strahl component with velocity distributions which often are very narrow in pitch-angle and are directed away from the Sun. Analysis of strahl distributions from 73.3 eV to 987 eV as measured by the SWEPAM plasma instrument on the ACE spacecraft are reported here. Although most previous observations show that the strahl pitch-angle width decreases with increasing energy, this presentation describes several events observed by ACE/SWEPAM at times of relatively enhanced magnetic fluctuations which show that this width increases as strahl energy increases. This presentation offers the hypothesis that this characteristic is due to strahl scattering by background whistler fluctuations. To test this hypothesis, second-order Vlasov theory calculations are presented which show that the whistler-strahl scattering rate should increase with increasing electron energy if magnetic power spectra are sufficiently steep functions of wavenumber and strahl energy distributions are sufficiently hard in energies parallel to the background magnetic field. ACE/SWEPAM measurements exhibit relatively hard strahl distributions, providing support to the whistler scattering hypothesis.
DE: 2159 Plasma waves and turbulence
DE: 2164 Solar wind plasma
DE: 7829 Kinetic waves and instabilities
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005