Cosmic-Ray Short Burst Observed with the Global Muon Detector Network (GMDN) on 2015 June 22
Year: 2018
Type: article
Abstract: We analyze the short cosmic-ray intensity increase (“cosmic-ray burst”: CRB) on 2015 June 22 utilizing a global network of muon detectors and derive the global anisotropy of cosmic-ray intensity and the density (i.e., the omnidirectional intensity) with 10 minute time resolution. We find that the CRB was caused by a local density maximum and an enhanced anisotropy of cosmic rays, both of which appeared in association with Earth’s crossing of the heliospheric current sheet (HCS). This enhanced anisotropy was normal to the HCS and consistent with a diamagnetic drift arising from the spatial gradient of cosmic-ray density, which indicates that cosmic rays were drifting along the HCS from the north of Earth. We also find a significant anisotropy along the HCS, lasting a few hours after the HCS crossing, indicating that cosmic rays penetrated into the inner heliosphere along the HCS. Based on the latest geomagnetic field model, we quantitatively evaluate the reduction of the geomagnetic cutoff rigidity and the variation of the asymptotic viewing direction of cosmic rays due to a major geomagnetic storm that occurred during the CRB and conclude that the CRB is not caused by the geomagnetic storm, but by a rapid change in the cosmic-ray anisotropy and density outside the magnetosphere.
Source: The Astrophysical Journal
Authors: K. Munakata, M. Kozai, P. Evenson, T. Kuwabara, C. Kato, M. Tokumaru, M. Rockenbach, A. Dal Lago, R. R. S. de Mendonca, C. R. Braga, N. J. Schuch, H. K. Al Jassar, M. M. Sharma, M. L. Duldig, J. E. Humble, I. Sabbah, J. Kóta
Institutions: Shinshu University, Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, University of Delaware, Institute for Space-Earth Environmental Research, Nagoya University, Nagoya University, Instituto Nacional de Pesquisas Espaciais, Chinese Academy of Sciences, National Space Science Center, State Key Laboratory of Space Weather, Kuwait University, University of Tasmania, Public Authority for Applied Education and Training, University of Arizona
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Aeronautics and Space Administration, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Kuwait University, Universidade Federal de Santa Maria, National Institute of Polar Research, National Oceanic and Atmospheric Administration, Goddard Space Flight Center, Australian Antarctic Division, Institute for Cosmic Ray Research, University of Tokyo
Awards: G7700111595, G8782356270
OpenAlex ID: W2885642904