Geotail Studies of Spiky Electric Fields in the Magnetotail

Tim Streed, C. A. Cattell (School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA)

F. Mozer (Space Sciences Laboratory, University of California, Berkeley, CA 94720)

K. Tsuruda, T. Yamamoto (ISAS, Sagamihara 229, Japan)

S. Kokubun (STELAB, Nagoya University, Toyokawa 442, Japan)

Large amplitude spiky electric fields have been observed in many regions of the magnetosphere, including the bow shock, auroral zone and plasma sheet boundary, and have been proposed to provide energization and heating of particles in these regions. We extend previous statistical studies to cover the region explored by the Geotail satellite. Results are presented on the occurrence frequency, location, association with density gradients, and magnetic field signatures of spiky electric fields in the magnetotail at radial distances of ~ 10-200 Re. Preliminary results show that spiky fields do not occur beyond ~100 Re and that they usually occur at or near the plasma sheet boundary (as indicated by changes in the spacecraft potential) and in association with waves near the lower hybrid frequency. Statistical analysis of the direction of the largest field amplitudes can yield information on the polarization of the waves and the spikes.These results provide constraints on the origin of the fields. The results will be described and compared to various possible generation mechanisms. In addition, the likely importance of these fields to magnetotail dynamics and particle energization will be discussed.

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