Rise time to maximum flux of relativistic solar electron events and its relation to the high-frequency component of the interplanetary field power spectrum

The time to maximum flux of 13 relativistic (β ≳ 0.8) solar electron events from western hemisphere flares is used to estimate the local scattering mean free path based on a propagation model with a radially constant diffusion coefficient. These electrons undergo resonance scattering by interplanetary magnetic field fluctuations corresponding to frequencies of ≳10−1 Hz at the orbit of the earth. It is found that the estimates of the electron mean free paths are quite consistent with the mean free paths calculated for rigidities P ∼ 310–369 Mv by Sari (1972) from interplanetary field power spectra when Sari's values are extrapolated to the electron rigidities (P ≲ 1 Mv). It is concluded that the variability from event to event in the time to maximum electron flux from western hemisphere flares is to be expected from the variability observed by Sari in the interplanetary field power spectra at the lower frequencies (≲10−3 Hz).