Associations between coronal mass ejections and solar energetic proton events

Abstract

We have used data from the Naval Research Laboratory (NRL) white light coronagraph on the P78‐1 spacecraft and energetic (E > 4 MeV) proton data from the Goddard Space Flight Center (GSFC) detectors on the IMP 8 and ISEE 3 spacecraft to investigate the association between proton events originating in flares and coronal mass ejections (CME's). The primary data were 50 prompt proton events observed between April 1979 and February 1982 for which reduced coronagraph data were available. H alpha flares could be confidently associated with 27 of these events, and in 26 of these 27 cases an associated CME was found, indicating a high but not perfect association of prompt proton events with CME's. Peak proton fluxes correlate with both the speeds and the angular sizes of the associated CME's. We show that the CME speeds do not significantly correlate with CME angular sizes, so that the peak proton fluxes are correlated with two independent CME parameters. With larger angular sizes, CME's are more likely to be loops and fans rather than jets and spikes and are more likely to intersect the ecliptic. Which of these factors is important to the peak proton flux correlation cannot be determined from the data. We find weak evidence that steeper proton spectra are associated with faster and wider CME's. Two of the 50 proton events of the study and two additional events, all with no associated CME's, share common characteristics: relatively short duration (∼1 day) proton events with low fluxes, parent flares with short (∼10 min) soft X ray duration, close magnetic connection to the earth, and gamma ray and metric type II emission.