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Published April 15, 1997 | Published
Journal Article Open

Are Energetic Electrons in the Solar Wind the Source of the Outer Radiation Belt?

Abstract

Using data from WIND, SAMPEX (Solar Anomalous, and Magnetospheric Particle Explorer), and the Los Alamos National Laboratory (LANL) sensors onboard geostationary satellites, we investigate the correlation of energetic electrons in the 20–200 keV range in the solar wind and of high speed solar wind streams with relativistic electrons in the magnetosphere to determine whether energetic electrons in the solar wind are the source of the outer relativistic electron radiation belt. Though there is some correlation between energetic electron enhancements in the solar wind and enhancements in the outer radiation belt, the phase space density of 20–200 keV electrons in the solar wind is not adequate to supply the outer radiation belt electrons. Although lower energy electrons in the solar wind could be a seed population of the outer radiation belt, such lower energy electrons cannot achieve relativistic energies through the normal process of radial transport which conserves the first adiabatic invariant. Thus additional internal acceleration processes are required within the magnetosphere to produce the outer radiation belt. High speed solar wind streams are well correlated with increased magnetic activity and with increased fluxes in the outer radiation belt. The maximum correlation between the high speed streams and the radiation belt flux occurs with an increasing time delay for higher energies and and lower L values. We conclude that acceleration processes within the magnetosphere which are well correlated with high speed solar wind streams are responsible for the outer radiation belt electrons.

Additional Information

Copyright 1997 by the American Geophysical Union. (Received October 29, 1996; accepted February 13, 1997.) We thank R. Lepping for providing WIND magnetic field data. Programming effort by Steve Monk is acknowledged. The work at University of Colorado was supported by NASA grant NAG5-2681, NAGW-5152, and NSF grant ATM-9624390. The work at University of California at Berkeley was supported by NASA grant NAG5-2815, NAGW-1098, NAG5-3198, and NSF grant ATM-9224688. The work at LANL was supported by DoE of Basic Energy Science. The work at the Aerospace Corporation was supported by NASA under Cooperative Agreement 26979B. The work at Calif. Inst. of Technology was supported by NASA grant NAS5-30704.

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