Gradual Solar Energetic Particle Event Associated with a Decelerating Shock Wave
L. Kocharov, T. Laitinen, A. Al-Sawad, O. Saloniemi, E. Valtonen, M. J. Reiner
On 2000 April 4-6 the Energetic and Relativistic Nuclei and Electron particle telescope on the Solar and Heliospheric Observatory spacecraft observed a major solar energetic particle (SEP) event associated with two coronal mass ejections (CMEs) separated by approximately 8 hr. The first CME was accompanied by a low- frequency type II radio burst observed by the WAVES receivers on the Wind spacecraft. Analysis of the high-precision measurements of the \raisebox-0.5ex\textasciitilde20 MeV proton flux anisotropy, model fitting of the type II dynamic spectrum, and SEP transport modeling support the idea that the shock wave of the first CME was an efficient accelerator for \raisebox-0.5ex\textasciitilde20 MeV protons during only the first 6 hr after the launch. This shock gradually slowed down, weakened, and became transparent for the protons produced by the second eruption behind the previous CME. The main production of SEPs due to the two successive eruptions continued together for 12 hr. The near-Earth SEP event was additionally amplified by the SEP mirroring in the interplanetary magnetic field draping at the edge of an old CME beyond the Earth's orbit, which made the SEP intensity-time profiles more prolonged than would be expected based on the assumption of SEP transport in the standard solar wind.
ApJl, 700, L51-L55, 2009