General Characteristics of High Energetic Proton Events Observed with SOHO/ERNE During Solar Cycle 23

Abstract

In the current work, the characteristics of the high energetic proton events were studied. We have selected 40 energetic proton events with intensities of two order of magnitude over the background in the logarithmic scale at 90-116 MeV detected by Energetic and Relativistic Nuclei and Electrons (ERNE) onboard SOHO during solar cycle 23. We examine the first injection time of those events through two methods, first by estimating the flight time of non-scattered protons of those nominal energies along the Archimedean field line of nominal length 1.2 AU. Secondly, we consider wide range of proton energies for the same events and assume a simultaneous release, and that the path length does not depend on the energies. We then compared the estimated times and heights with related flare and coronal mass ejection (CME) characteristics. We found that all events were associated with Coronal Mass Ejections (CMEs) observed simultaneously with Large Angle and Spectrometric Coronagraph (LASCO) and solar flares observed with soft X-ray telescope onboard GOES. The speed and angular width is higher for those CMEs which were associated with X class flare than those which were associated with M class flare and C class flare. Most of the first protons injected while the CMEs were below 5 solar radii and most of the protons reach their maximum intensity while the CMEs were above 10 solar radii and that the maximum intensities have been achieved much earlier than the possible IP shock passage.