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Observations of 1-6 MeV Jovian electrons at 1 AU and a study of their propagation

Citation

Hartman, Steward Russell (1979) Observations of 1-6 MeV Jovian electrons at 1 AU and a study of their propagation. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:10092014-094710787

Abstract

The 1-6 MeV electron flux at 1 AU has been measured for the time period October 1972 to December 1977 by the Caltech Electron/Isotope Spectrometers on the IMP-7 and IMP-8 satellites. The non-solar interplanetary electron flux reported here covered parts of five synodic periods. The 88 Jovian increases identified in these five synodic periods were classified by their time profiles. The fall time profiles were consistent with an exponential fall with τ ≈ 4-9 days. The rise time profiles displayed a systematic variation over the synodic period. Exponential rise time profiles with τ ≈ 1-3 days tended to occur in the time period before nominal connection, diffusive profiles predicted by the convection-diffusion model around nominal connection, and abrupt profiles after nominal connection.

The times of enhancements in the magnetic field, │B│, at 1 AU showed a better correlation than corotating interaction regions (CIR's) with Jovian increases and other changes in the electron flux at 1 AU, suggesting that │B│ enhancements indicate the times that barriers to electron propagation pass Earth. Time sequences of the increases and decreases in the electron flux at 1 AU were qualitatively modeled by using the times that CIR's passed Jupiter and the times that │B│ enhancements passed Earth.

The electron data observed at 1 AU were modeled by using a convection-diffusion model of Jovian electron propagation. The synodic envelope formed by the maxima of the Jovian increases was modeled by the envelope formed by the predicted intensities at a time less than that needed to reach equilibrium. Even though the envelope shape calculated in this way was similar to the observed envelope, the required diffusion coefficients were not consistent with a diffusive process.

Three Jovian electron increases at 1 AU for the 1974 synodic period were fit with rise time profiles calculated from the convection-diffusion model. For the fits without an ambient electron background flux, the values for the diffusion coefficients that were consistent with the data were kx = 1.0 - 2.5 x 1021 cm2/sec and ky = 1.6 - 2.0 x 1022 cm2/sec. For the fits that included the ambient electron background flux, the values for the diffusion coefficients that were consistent with the data were kx = 0.4 - 1.0 x 1021 cm2/sec and ky = 0.8 - 1.3 x 1022 cm2/sec.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Stone, Edward C.
Group:Space Radiation Laboratory
Thesis Committee:
  • Unknown, Unknown
Defense Date:14 May 1979
Record Number:CaltechTHESIS:10092014-094710787
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:10092014-094710787
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8682
Collection:CaltechTHESIS
Deposited By: Benjamin Perez
Deposited On:09 Oct 2014 17:22
Last Modified:20 Oct 2014 18:02

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