Abstract
We investigate the characteristics of Galactic cosmic rays in events associated with magnetic clouds that reach Earth. A mathematical model, capable of describing the distribution of the cosmic-ray density in a magnetic cloud is considered. We show that in most cases the behavior of the cosmic-ray density within magnetic clouds at 1 AU can be described accurately by a parabolic function of the distance to the center of the magnetic cloud measured in gyroradii. As expected, the majority of magnetic clouds modulate cosmic rays, resulting in a reduction of their density. However, there is a group of events (about one fifth of the total sample) in which the density of cosmic rays in a magnetic cloud increases. Furthermore, the extremum (a minimum or a maximum) of the cosmic-ray density is found closer to the cloud center and not at its edges. We consider a number of the factors contributing to the model and estimate the effect of each factor.
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Acknowledgements
The authors would like to thank the anonymous referee, whose thoughtful comments contributed significantly to this article. Furthermore, the authors are thankful to collaborators of the worldwide network of CR stations for providing the data and continuously monitoring of the neutron component: http://cr0.izmiran.ru/ThankYou/ . The NMDB database ( www.nmdb.eu ), founded under the European Union’s FP7 programme, is gratefully acknowledged (contract no. 213007) for the provision of data.
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Belov, A., Abunin, A., Abunina, M. et al. Galactic Cosmic Ray Density Variations in Magnetic Clouds. Sol Phys 290, 1429–1444 (2015). https://doi.org/10.1007/s11207-015-0678-z
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DOI: https://doi.org/10.1007/s11207-015-0678-z