Observations of Jovian electrons at 1 AU

It has recently been suggested that electrons of Jovian origin are responsible for the ‘quiet time increases’ in the >3-MeV electron intensity observed at 1 AU. Using data from the California Institute of Technology electron/isotope spectrometers on Imp 7 and 8, we have studied the temporal behavior of quiet time electrons at 1 AU over the period October 1972 through May 1975. We find the 1- to 6-MeV electron intensity to vary by a factor of ∼10 from one quiet time period to another, including numerous short-term enhancements characteristic of the quiet time increases reported during 1964–1972. The magnitude and frequency of the increases grow abruptly and remain high for a ∼4-month period beginning with the time at which the interplanetary field line first connects earth and Jupiter. It is suggested that the interconnection of the interplanetary field with an extended Jovian magnetotail of ∼2 AU in length could result in the observed longitudinal distribution of Jovian electrons at 1 AU.