Premium
Relativistic solar cosmic rays during the current sunspot cycle
Author(s) -
Pomerantz M. A.,
Duggal S. P.
Publication year - 1978
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl005i010p00877
Subject(s) - forbush decrease , physics , cosmic ray , astrophysics , sunspot , neutron monitor , solar cycle 23 , solar flare , solar cycle 22 , solar cycle , flare , solar minimum , solar cycle 24 , astronomy , coronal mass ejection , solar wind , nuclear physics , plasma , magnetic field , quantum mechanics
Four ground level enhancements (GLE) have occurred during the ascending phase of solar cycle 21. The first two, on September 19 and 24, 1977, emanated from the same active region belonging to the old cycle more than a year after sunspot minimum. Evaluation of data recorded during the November 22, 1977, GLE reveals that the attenuation length for particles detected by an atmospheric neutron detector is 88 gm/cm² compared with 100 gm/cm² for the standard lead‐polyethylene pile. The increased response to relativistic solar cosmic rays is displayed in all four events. The May 7, 1978, GLE was highly anisotropic over an extended period. Observations to date show that small GLEs (<25%) are equally likely to occur during Forbush decreases or quiet periods, whereas larger GLEs are concurrent with a preexisting cosmic ray storm. As in the case of other manifestations of solar activity, there is a marked north‐south asymmetry in the heliolatitude of GLE‐producing flares.