Open AccessA search for two‐component energetic proton events observed on board SOHO
Author(s) -
AlSawad Amjad,
Torsti Jarmo,
Kocharov Leon,
HuttunenHeikinmaa Kalle
Publication year - 2006
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005ja011362
Subject(s) - physics , astrophysics , interplanetary spaceflight , dispersion (optics) , range (aeronautics) , proton , abundance (ecology) , velocity dispersion , interplanetary medium , solar wind , astronomy , computational physics , atmospheric sciences , plasma , nuclear physics , optics , materials science , fishery , galaxy , composite material , biology
We examined solar energetic particle (SEP) events from May 1996 through April 2000 that showed evidence for two peaks of intensity, separated by 3–24 hours, in the energy range ∼1–20 MeV, observed with the Energetic and Relativistic Nuclei and Electron instrument (ERNE) onboard Solar and Heliospheric Observatory (SOHO). Of 88 clear SEP events observed, 18 exhibited such double peaks, with more than factor of two dips between the peaks in the energy range up to at least 8 MeV. Second peaks were examined in terms of velocity dispersion and change of 4 He/p abundance ratio. Three events showed both velocity dispersion and abundance change, four events just an abundance change, and four showed velocity dispersion and no abundance change. We discuss how these different properties may reflect acceleration processes near the Sun and in the interplanetary medium. In the remaining seven events with neither velocity dispersion nor abundance change, we suggest that the second peak was a spatial feature caused by interplanetary magnetic field structures.