Open AccessEvidence for charge drift modulation at intermediate solar activity from the flux variation of protons and α particles
Author(s) -
Boella G.,
Gervasi M.,
Mariani S.,
Rancoita P. G.,
Usoskin I. G.
Publication year - 2001
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 - 10.1029/2001ja900075
Subject(s) - cosmic ray , physics , flux (metallurgy) , polarity (international relations) , polarity symbols , solar cycle , proton , neutron monitor , solar minimum , helium , solar energetic particles , atomic physics , astrophysics , nuclear physics , plasma , coronal mass ejection , solar wind , voltage , materials science , quantum mechanics , genetics , biology , metallurgy , breakdown voltage , cell
We have studied the flux of galactic protons and helium nuclei measured at 1 AU along two consecutive solar activity cycles. We have correlated cosmic ray fluxes measured on IMP 8 satellite at low energy (50 – 300 MeV amu −1 ) with neutron monitor counts registered at Climax station (at energies above few GeV) during the period 1973 – 1995. We have found a systematic excess in the flux of the positive charged particles during the periods with positive solar magnetic field polarity ( A > 0) with respect to the flux during the periods of negative polarity ( A < 0). This flux excess gives an experimental evidence that charge drift effect plays an important role in the modulation of galactic cosmic rays. A systematic investigation of charge drift modulation is presented. The dependence of the drift effect on the solar activity phase arid the particle energy has been also studied. A variation of the proton (as well as helium) flux might be as large as 40%, at the solar activity minimum of two contiguous cycles, at energy ≤ 100 MeV.