GEOPHYSICAL RESEARCH LETTERS, VOL. 25, NO. 12,
JUNE 15, 1998
The association of electrostatic ion cyclotron waves, ion
and electron beams and field-aligned currents: FAST
observations of an auroral zone crossing near midnight
C. Cattell1, R. Bergmann2, K. Sigsbee1,
C. Carlson3, C. Chaston3, R. Ergun3, J.
McFadden3, F. S. Mozer3, M. Temerin3,
R. Strangeway4, R. Elphic5, L. Kistler6, E.
Moebius6, L. Tang6, D. Klumpar7, R.
1School of Physics and Astronomy, University of Minnesota,
2Department of Physics, Eastern Illinois University, Charleston, IL
3Space Sciences Laboratory, University of California, Berkeley,
4Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, CA
5Space and Atmospheric Sciences, Los Alamos National Lab Los
6University of New Hampshire, Durham, NH
7Lockheed/Martin Research Laboratory, Palo Alto, CA
8NASA/GSFC, Laboratory for Extraterrestrial Physics, Greenbelt,
ABSTRACT. FAST particle and wave data for a single
nightside auroral zone crossing are utilized to examine the free
energy source for electrostatic ion cyclotron (EIC) waves.
Comparisons of the unstable wave modes, obtained by an
electrostatic linear dispersion relation solver, to the observed
waves for two intervals with upflowing ion beams and two
with upflowing electron beams are consistent with the
conclusion that the observed waves near the cyclotron
frequencies are EIC which are driven by the electron drift both
in the upgoing ion beam regions and in the upgoing electron
regions. A limitation is that the drifting bi-Maxwellian model
used in the dispersion relation is not a good match to the
observed upflowing electron distributions. The observed ion
beams do not drive EIC waves; however, the relative drift of
the various ion species comprising the ion beam can drive low
frequency (<~50 Hz) waves unstable. The electron drift, during
some intervals, also destabilizes electron acoustic waves.