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A peculiar ICME event in August 2018 observed with the Global Muon Detector Network


Kihara, W and Munakata, K and Kato, C and Kataoka, R and Kadokura, A and Miyake, S and Kozai, M and Kuwabara, T and Tokumaru, M and Mendonca, RRS and Echer, E and Lago, AD and Rockenbach, M and Schuch, NJ and Bageston, JV and Braga, CR and Al Jassar, HK and Sharma, MM and Duldig, ML and Humble, JE and Evenson, P and Sabbah, I and Kota, J, A peculiar ICME event in August 2018 observed with the Global Muon Detector Network, Space Weather, 19, (3) Article e2020SW002531. ISSN 1539-4956 (2021) [Refereed Article]

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This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND 4.0) License, (, which permits use and distribution in any medium, provided the original work is properly cited, the use is non- commercial and no modifications or adaptations are made

DOI: doi:10.1029/2020SW002531


We demonstrate that global observations of high-energy cosmic rays contribute to understanding unique characteristics of a large-scale magnetic flux rope causing a magnetic storm in August 2018. Following a weak interplanetary shock on August 25, 2018, a magnetic flux rope caused an unexpectedly large geomagnetic storm. It is likely that this event became geoeffective because the flux rope was accompanied by a corotating interaction region and compressed by high-speed solar wind following the flux rope. In fact, a Forbush decrease was observed in cosmic-ray data inside the flux rope as expected, and a significant cosmic-ray density increase exceeding the unmodulated level before the shock was also observed near the trailing edge of the flux rope. The cosmic-ray density increase can be interpreted in terms of the adiabatic heating of cosmic rays near the trailing edge of the flux rope, as the corotating interaction region prevents free expansion of the flux rope and results in the compression near the trailing edge. A northeast-directed spatial gradient in the cosmic-ray density was also derived during the cosmic-ray density increase, suggesting that the center of the heating near the trailing edge is located northeast of Earth. This is one of the best examples demonstrating that the observation of high-energy cosmic rays provides us with information that can only be derived from the cosmic ray measurements to observationally constrain the three-dimensional macroscopic picture of the interaction between coronal mass ejections and the ambient solar wind, which is essential for prediction of large magnetic storms.

Item Details

Item Type:Refereed Article
Keywords:cosmic rays, space weather, ICME, muon telescope
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:High energy astrophysics and galactic cosmic rays
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Duldig, ML (Dr Marc Duldig)
UTAS Author:Humble, JE (Dr John Humble)
ID Code:143038
Year Published:2021
Web of Science® Times Cited:3
Deposited By:Physics
Deposited On:2021-02-23
Last Modified:2021-09-21
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