HR: 17:08h
AN: SM24A-05    [Abstracts]
TI: Current Carriers in the Earth's Auroral Zone: Implications for Jovian Aurora
AU: * Strangeway, R J
EM: strange@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095 United States
AU: Khurana, K K
EM: kkhurana@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095 United States
AU: Elphic, R C
EM: relphic@lanl.gov
AF: ISR-1, Space and Atmospheric Sciences, Mail Stop D466, Los Alamos National Laboratory, Los Alamos, NM 87545 United States
AB: Recent observations of X-ray emissions at Jovian polar latitudes have been cited as evidence of intense ion precipitation into the Jovian ionosphere. The ions have further been argued as being current carriers in regions of downward field-aligned current. The currents are thought to be generated either by reconnection, or by processes internal to the Jovian magnetosphere. Terrestrial aurora are also associated with field-aligned current systems. The inverted-V aurora are usually observed in regions of upward field-aligned current, and the current is carried by the precipitating electrons. Measurements by the FAST spacecraft have shown remarkably good agreement between the current as determined by the number flux of precipitating electrons and the current as inferred by the gradient of the magnetic field. There is generally less of an agreement between particle fluxes and magnetometer measurements in the return current region. This appears to be because the particle detectors do not measure electrons at sufficiently low energies. At times the electrons are accelerated upwards to high enough energy to be measured by FAST, and again reasonable agreement is found. Invoking ions as current carriers does not explain the discrepancies in downward current regions. Plasma sheet ions are usually observed at the same time as the downward currents, and they show no evidence of downward acceleration. Terrestrial observations therefore suggest that auroral currents are carried by electrons in both downward and upward current regions. Ions do not carry any significant field-aligned current. This raises questions concerning the ion current hypothesis as applied to the Jovian X-ray emissions. Processes other than acceleration in field-aligned potentials may have to be invoked to explain the ion energization at Jupiter.
DE: 2704 Auroral phenomena (2407)
DE: 2708 Current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2756 Planetary magnetospheres (5443, 5737, 6030)
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting