Cosmic-Ray Short Burst Observed with the Global Muon Detector Network (GMDN) on 2015 June 22

• Published in: The Astrophysical Journal
• Main Authors: Munakata, K., Kozai, M., Evenson, P., Kuwabara, T., Kato, C., Tokumaru, M., Rockenbach, M., Lago, A. Dal, de Mendonca, R. R. S., Braga, C. R., Schuch, N. J., Jassar, H. K. Al, Sharma, M. M., Duldig, M. L., Humble, J. E., Sabbah, I., Kóta, J.
• Other Authors: Univ Arizona, Lunar & Planetary Lab
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP PUBLISHING LTD 2018
• Subjects: cosmic rays; interplanetary medium; Sun: coronal mass ejections (CMEs); Antarctic; Antarc*; Australian Antarctic Division
• Online Access: http://hdl.handle.net/10150/631091; https://doi.org/10.3847/1538-4357/aacdfe

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. Institute for Space-Earth Environmental Research (ISEE), Nagoya University; Institute for Cosmic Ray Research (ICRR), University of Tokyo; Nagoya University; CAPES; INPE; UFSM; Sao Martinho da Serra muon detector; Australian Antarctic Division; Hobart muon detector; Research Administration of Kuwait University [SP01/09]; CNPq [304209/2014/7, 152050/2016-7]; Sao Paulo Research Foundation [14/24711-6]; China-Brazil Joint Laboratory for Space Weather; Joint Research Program of the Institute for Space-Earth Environmental Research, Nagoya University, Japan This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [e-mail].