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Ann. Geophys., 24, 1829-1837, 2006
www.ann-geophys.net/24/1829/2006/
© European Geosciences Union 2006
Parallel electric fields inferred during a pulsating aurora
J. D. Williams1, E. MacDonald2, M. McCarthy3, L. Peticolas4, and G. K. Parks4
1Dept. of Physics and Astronomy, University of Montana, Missoula, Montana 59812, USA
2Los Alamos National Laboratory, Los Alamos, NM 87545, USA
3Dept. of Earth and Space Sciences, University of Washington, Seattle, Wa. 98195, USA
4University of California, Berkeley Space Science Laboratory, Berkeley, CA 94720-7450, USA
Abstract. A sounding rocket, equipped to study pulsating aurora launched from
Poker Flat, Alaska on 13 March 1997 at 10:20:31 UT, measured
electron precipitation over the range ~10 eV to 500 keV covering
pitch-angles from 0 to 180°. Data show electrons with
energies <1 keV are mostly secondaries produced below the rocket
altitude by the higher energy precipitated electrons. We observed
nearly equal fluxes of up and down going electrons for energies
<1 keV at altitudes from 265 to 380 km. Electron transport
simulation results indicate the secondaries produced by the more
energetic electrons will have two times higher flux in the upward
direction as compared to the downward direction. Our observations of
nearly equal fluxes of up and downgoing electrons over a large range
of altitudes is consistent with the presence of an electric potential
above the rocket that reflects the upgoing electrons back toward the
rocket where they are detected as downward going electrons. The
strength of the potential is estimated to be 1.5±0.5 kV and its
location is no greater than 5000km above the rocket. Finally, the
inferred potential drop exists independently of the presence of
pulsations.
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