The 1-6 MeV electron flux at 1 AU has been measured for thetime period October 1972 to December 1977 by the CaltechElectron/Isotope Spectrometers on the IMP-7 and IMP-8 satellites.The non-solar interplanetary electron flux reported here coveredparts of five synodic periods. The 88 Jovian increases identifiedin these five synodic periods were classified by their time profiles.The fall time profiles were consistent with an exponential fallwith τ ≈ 4-9 days. The rise time profiles displayed a systematicvariation over the synodic period. Exponential rise time profileswith τ ≈ 1-3 days tended to occur in the time period before nominalconnection, diffusive profiles predicted by the convection-diffusionmodel around nominal connection, and abrupt profiles after nominalconnection.
The times of enhancements in the magnetic field, │B│, at 1 AUshowed 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 toelectron propagation pass Earth. Time sequences of the increases anddecreases in the electron flux at 1 AU were qualitatively modeled byusing 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 aconvection-diffusion model of Jovian electron propagation. Thesynodic envelope formed by the maxima of the Jovian increases wasmodeled by the envelope formed by the predicted intensities at atime less than that needed to reach equilibrium. Even though theenvelope shape calculated in this way was similar to the observedenvelope, the required diffusion coefficients were not consistentwith a diffusive process.
Three Jovian electron increases at 1 AU for the 1974 synodicperiod were fit with rise time profiles calculated from theconvection-diffusion model. For the fits without an ambientelectron background flux, the values for the diffusion coefficientsthat were consistent with the data were kx = 1.0 - 2.5 x 1021 cm2/secand ky = 1.6 - 2.0 x 1022 cm2/sec. For the fits that included theambient electron background flux, the values for the diffusioncoefficients that were consistent with the data werekx = 0.4 - 1.0 x 1021 cm2/sec and ky = 0.8 - 1.3 x 1022 cm2/sec.
