The primary cosmic ray electron spectrum 1978-1980
In August of 1978 the ISEE-3 spacecraft carried the University of Chicago electron spectrometer into interplanetary space. Strong intensity variations of Jovian electrons have been observed in the energy range from 5 to 25 MeV in conjunction with 3 Jovian seasons. The spectral shape of the extra electrons has a shallow maximum around 15 MeV. No measurable long term variation in the average electron spectrum has been observed since 1968 up to energies of about 50 MeV. However, strong solar cycle modulation occurs at energies around a few hundred MeV.
Evenson, P.↗