Modelling formation of new radiation belts and response to ULF oscillations following March 24, 1991 SSC
- Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire (United States)
- Space Sciences Laboratory, University of California, Berkeley, California (United States)
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota (United States)
- Space Sciences Department, The Aerospace Corporation, Los Angeles, California (United States)
- Phillips Laboratory, Hanscom AFB, Massachusetts (United States)
- Solar-Terrestrial Environment Laboratory, Nagoya University (Japan)
The rapid formation of a new proton radiation belt at {ital L}{approx_equal}2.5 following the March 24, 1991 Storm Sudden Commencement (SSC) observed at the CRRES satellite is modelled using a relativistic guiding center test particle code. The new radiation belt formed on a time scale shorter than the drift period of eg. 20 MeV protons. The SSC is modelled by a bipolar electric field and associated compression and relaxation in the magnetic field, superimposed on a background dipole magnetic field. The source population consists of solar protons that populated the outer magnetosphere during the solar proton event that preceeded the SSC and trapped inner zone protons. The simulations show that both populations contribute to drift echoes in the 20{endash}80 MeV range measured by the Aerospace instrument and in lower energy channels of the Protel instrument on CRRES, while primary contribution to the newly trapped population is from solar protons. Proton acceleration by the SSC differs from electron acceleration in two notable ways: different source populations contribute and nonrelativistic conservation of the first adiabatic invariant leads to greater energization of protons for a given decrease in {ital L} than for relativistic electrons. Model drift echoes, energy spectra and flux distribution in {ital L} at the time of injection compare well with CRRES observations. On the outbound pass, {approximately}2 hours after the SSC, the broad spectral peak of the new radiation belt extends to higher energies (20{endash}40 MeV) than immediately after formation. Electron flux oscillations observed at this later time are attributed to post-SSC impulses evident in ground magnetograms, while two minute period ULF oscillations also evident in CRRES field data appear to be cavity modes in the inner magnetosphere. {copyright} {ital 1996 American Institute of Physics.}
- OSTI ID:
- 451684
- Report Number(s):
- CONF-9408182--
- Journal Information:
- AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 383; ISSN 0094-243X; ISSN APCPCS
- Country of Publication:
- United States
- Language:
- English
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