Drift effects and the average features of cosmic ray density gradient in CIRs during successive two solar minimum periods
Abstract
We deduce on hourly basis the spatial gradient of the cosmic ray density in three dimensions from the directional anisotropy of high-energy (~50 GeV) galactic cosmic ray (GCR) intensity observed with a global network of muon detectors on the Earth's surface. By analyzing the average features of the gradient in the corotational interaction regions (CIRs) recorded in successive two solar activity minimum periods, we find that the observed latitudinal gradient (Gz) changes its sign from negative to positive on the Earth's heliospheric current sheet (HCS) crossing from the northern to the southern hemisphere in A<0 epoch, while it changes from positive to negative in A>0 epoch. This is in accordance with the drift prediction. We also find a negative enhancement in Gx after the HCS crossing in both A<0 and A>0 epochs, but not in Gy. This asymmetrical feature of Gx and Gy indicates significant contributions from the parallel and perpendicular diffusions to the the gradient in CIRs in addition to the contribution from the drift effect.
Keywords
Cite
@article{arxiv.0912.4859,
title = {Drift effects and the average features of cosmic ray density gradient in CIRs during successive two solar minimum periods},
author = {A. Fushishita and Y. Okazaki and T. Narumi and C. Kato and S. Yasue and T. Kuwabara and J. W. Bieber and P. Evenson and M. R. Da Silva and A. Dal Lago and N. J. Schuch and M. Tokumaru and M. L. Duldig and J. E. Humble and I. Sabbah and J. Kota and And K. Munakata},
journal= {arXiv preprint arXiv:0912.4859},
year = {2020}
}
Comments
11 pages, 1 table, 5 figures, Proc. of AOGS 2008, accepted for the publication on the Advances in Geoscience, 2010