Solar Cosmic Ray Acceleration by a Shock Wave in the Lower Solar Corona on May 7, 1978

Abstract

Based on the theory of diffusive shock acceleration of charged particles, we have theoretically studied the spectra of protons produced by a shock wave driven by a coronal mass ejection (CME) in the lower solar corona with known solar plasma parameters for the solar cosmic ray (SCR) event recorded near the Earth’s orbit on May 7, 1978 (ground level enhancement no. 31, GLE31) using numerical methods. The proton flux data from the CPME instrument installed on the IMP-8 spacecraft and the worldwide network of ground-based neutron monitors combined with the particle measurements by the telescopes on the IMP-7 and IMP-8 satellites have been used to analyze the event. In our calculations, to satisfactorily reproduce the proton spectrum measured at the Earth’s orbit, the CME velocity was assumed to be constant and equal to 600 km s–1. The shock acceleration of SCRs proceeded up to 1.4 R⊙ solar radii for 256 s.