Analysis of multi-eruption solar energetic particle events (MESEP) on March 17-18, 2003

: F. Al-Hamadani, A. Al-Sawad, E. Valtonen, S. Pohjolainen

: International Cosmic Ray Conference

: 2015

: POS Proceedings of Science

: 084

: http://pos.sissa.it/archive/conferences/236/084/ICRC2015_084.pdf

On March 17-18, 2003 the Energetic and Relativistic Nuclei and Electrons (ERNE) instrument

on board the Solar and Heliospheric Observatory (SOHO) spacecraft observed three solar energetic particle (SEP) events in rapid succession (within s26 hours) from the same active region. The first event was weak and proton intensity enhancement was observed only below about 25 MeV. No coincident coronal mass ejection (CME) was found, but the event can be associated with an impulsive Ha flare starting at 10:09 UT on March 17 at location S16W33 and with type III radio burst. The second particle event was associated with an X1.5-class X-ray flare starting on March 17 at 18:50 UT and a fast and wide (1020 km/s, 96) CME. The CME has been reported to be radio quiet. Enhanced proton intensities reached up to 60 MeV. The third SEP event occurred about 18 hours later on the tail of the second one, reached proton energies up to s60 MeV, and lasted for roughly 2 days at energies >10 MeV. The event was associated with another X1.5-class flare, fast and wide (1601 km/s, 206) CME, and decametric-hectometric type II radio burst. This last event was associated with a shock observed at the Advanced Composition Explorer (ACE) spacecraft on March 19. We analyse these particle events based on the velocity dispersion of the particles, helium-to-proton ratio, and the observed anisotropy of the particle intensities.

Keywords: Coronal mass ejections, type II radio bursts, solar energetic particle events.