HR: 10:50h
AN: SH12A-03    [Abstracts]
TI: Counterstreaming Suprathermal Electrons Within Coronal Hole Fast Flows Measured at 1 AU by ACE and Genesis
AU: * Steinberg, J T
EM: jsteinberg@lanl.gov
AF: Los Alamos National Laboratory, Space and Atmospheric Sciences D466, Los Alamos, NM 87545 United States
AU: Gosling, J T
AF: Los Alamos National Laboratory, Space and Atmospheric Sciences D466, Los Alamos, NM 87545 United States
AU: de Koning, C A
AF: Los Alamos National Laboratory, Space and Atmospheric Sciences D466, Los Alamos, NM 87545 United States
AU: Skoug, R M
AF: Los Alamos National Laboratory, Space and Atmospheric Sciences D466, Los Alamos, NM 87545 United States
AU: Wiens, R C
AF: Los Alamos National Laboratory, Space and Atmospheric Sciences D466, Los Alamos, NM 87545 United States
AB: Counterstreaming suprathermal electrons are observed on open interplanetary field lines within some coronal hole fast streams observed at 1 AU with ACE and Genesis. An anti-sunward directed electron beam produced by suprathermal electrons escaping from the solar corona, and commonly referred to as the strahl, is continuously present. In addition, a sunward-directed beam is often present in the fast streams. We attribute the sunward-directed beam to electrons that leak from co-rotating interaction regions (CIRs) at greater heliocentric distances and travel sunward along the interplanetary magnetic field. The sunward-directed flux often exceeds the anti-sunward strahl flux, especially at the measurement energies 980 eV and 1.4 keV. The counterstreaming is observed immediately after the passage of CIR, whether it is bounded by a reverse shock, or a reverse wave that has not yet steepened into a shock. The counter-streaming may also be found hours to days after the onset of the fast stream, indicating a more distant magnetic connection to a CIR. Electron counterstreaming within co-rotating high speed flows on field lines which are open, but connected to CIRs, was reported in earlier work for Ulysses measurements made beyond 2 AU. However it was previously thought that such counterstreaming was unlikely to be important near 1 AU. We present observations of counterstreaming electrons within very regular recurrent fast streams observed from December 1999 to March 2000 and from January through March 2002. In addition we show intervals of counterstreaming within comparatively irregular fast streams during 2003. We find that the intensity and energy extent of the sunward beams is more variable from one solar rotation to the next for the 2003 episodes than for the earlier episodes. LA-UR-04-6195
DE: 7511 Coronal holes
DE: 2102 Corotating streams
DE: 2114 Energetic particles, heliospheric (7514)
DE: 2134 Interplanetary magnetic fields
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting