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Average features of the interplanetary shock observed with the Global Muon Detector Network


Kozai, M and Munakata, K and Kato, C and Kuwabara, T and Rockenbach, M and Dal Lago, A and Schuch, NJ and Al Jassar, HK and Sharma, MM and Duldig, ML and Humble, JE and Bieber, JW and Evenson, P and Sabbah, I and Tokumaru, M, Average features of the interplanetary shock observed with the Global Muon Detector Network, Proceedings of Science, 30 July - 06 August, The Hague, Netherlands, pp. 1-8. ISSN 1824-8039 (2015) [Non Refereed Conference Paper]

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From three-dimensional spatial density gradient of galactic cosmic rays (GCRs) observed with the Global Muon Detector Network (GMDN), we derive average features of the GCR depleted region behind the IP (interplanetary) shock. We identify 207 IP-shocks that passed the earth based on the geomagnetic storm sudden commencements (SSCs) and extract 50 events that are associated with solar coronal mass ejections (CMEs) in a period between 2006 and 2014. From the first order GCR anisotropy corrected for the solar wind convection and Compton-Getting effect arising from the earth’s orbital motion, we deduce the density gradient on an hourly basis for each event. We then derive the average temporal variation of the density gradient by superposing its variations at the SSC onset timing. We confirm that the density gradient components are clearly enhanced after the shock passage, indicating the existence of GCR depleted region behind the shock which causes the Forbush Decrease in the cosmic ray intensity. The enhancement of the radial gradient shows longer duration when the earth has encountered the western flank of the shock, implying an asymmetric shielding effect of the shock on the GCRs. The longitudinal gradient, on the other hand, shows that the GCR density minimum is located around the longitudinal center behind the shock, which can be ascribed to the centered ejecta driving IP-shock.

Item Details

Item Type:Non Refereed Conference Paper
Keywords:cosmic rays: ICME, shocks, Forbush decreases
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:110301
Year Published:2015
Deposited By:Mathematics and Physics
Deposited On:2016-07-23
Last Modified:2016-08-05

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