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Acceleration Processes in the Cusp: Observations by the FAST SatelliteThe Fast Auroral Snapshot (FAST) spacecraft has encountered the Earth's cusp regions near its apogee of 4175 km on numerous occasions during its first two and half years of operations. The cusp encounters are identified by their signatures of keV dispersed ion injections of solar wind origin. The FAST instruments reveal a complex microphysics inherent to many, but not all, of the cusp regions encountered by the spacecraft, that often include upgoing ion beams within regions of downgoing electrons that may appear as series of inverted-V features with energies near a few hundred eV. In many instances, upgoing electron beams have also been observed. Intense (> 100 mV/m) spikey DC-coupled electric fields and plasma waves are common features of the cusp encounters which also provide evidence for the presence of such local acceleration processes. In some cases, the FAST data show clear modulation of the precipitating magnetosheath ions indicative that they are affected by local electric potentials, as evidenced by simultaneous electron acceleration within such intervals. Furthermore, the acceleration events are sometimes organized with an apparent cellular structure that suggest Alfv6n waves or other large scale phenomena are controlling the localized potentials. We examine several cusp encounters in detail in order to study the complex relation of the cusp energetic particle populations with the plasma waves and DC electric fields.
Document ID
19990081108
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Pfaff, R. F.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Carlson, C.
(California Univ. Berkeley, CA United States)
McFadden, J.
(California Univ. Berkeley, CA United States)
Ergun, R.
(California Univ. Berkeley, CA United States)
Clemmons, J.
(Aerospace Corp. El Segundo, CA United States)
Klumpar, D.
(Lockheed Martin Corp. Palo Alto, CA United States)
Moebius, E.
(New Hampshire Univ. Durham, NH United States)
Elphic, R.
(Los Alamos National Lab. NM United States)
Strangeway, R.
(California Univ. Los Angeles, CA United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Geophysics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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