Open AccessA comparison of cosmic ray intensities near the Earth at the sunspot minima in 1976 and 1987 and during 1995 and 1996
Author(s) -
Lockwood J. A.,
Webber W. R.
Publication year - 1997
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 - 10.1029/97ja01447
Subject(s) - heliosphere , cosmic ray , physics , astrophysics , sunspot , proton , helium , solar minimum , astronomy , magnetic field , solar wind , solar cycle , nuclear physics , atomic physics , quantum mechanics
The cosmic ray proton and helium intensities measured on the IMP spacecraft near the Earth from ∼ 45 MeV to several hundred MeV in April 1996 indicate that the intensities have recovered to almost the same maximum values they had at the last sunspot minimum. The 1996 intensities near the Earth are an even closer match to those observed two 11‐year cycles earlier in 1976. This confirming evidence of a 22‐year periodicity in the low‐energy cosmic ray intensities and spectral shapes is attributed to the effects of the difference in the entry of cosmic rays into the heliosphere as well as their different drift motion inside the heliosphere as a consequence of the 22‐year periodicity in the solar magnetic field. This observation thus suggests that drifts play a significant role in the cosmic ray modulation process.