Open AccessSolar Longitude Distribution of High-energy Proton Flares: Fluences and Spectra
Author(s) -
E. W. Cliver,
Florian Mekhaldi,
Raimund Muscheler
Publication year - 2020
Publication title -
the astrophysical journal. letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.639
H-Index - 201
eISSN - 2041-8213
pISSN - 2041-8205
DOI - 10.3847/2041-8213/abad44
Subject(s) - physics , astrophysics , solar flare , coronal mass ejection , spectral line , flare , longitude , astronomy , plasma , solar wind , latitude , nuclear physics
The distribution of the longitudes of solar flares associated with the high-energy proton events called ground level events (GLEs) can be approximated by a Gaussian with a peak at ∼W60, with a full range from ∼E90 to ∼W150. The longitudes of flares associated with the top third (24 of 72) of GLEs in terms of their >430 MeV fluences ( F 430 ) are primarily distributed over E20–W100 with a skew toward disk center. This 120° span in longitude is comparable to the latitudinal spans of powerful coronal mass ejections (CMEs) from limb flares. Only 5 of 24 strong GLEs are located within the W40–80 zone of good magnetic connection to Earth. GLEs with hard spectra, i.e., a spectral index SI 30/200 (= log( F 30 / F 200 )) W100) GLEs; (2) quasi-parallel shock acceleration for well-connected (W40–80) GLEs, and (3) proton acceleration/trapping at CME-driven bow shocks from central meridian (E20–W20) that strike the Earth.