AVERAGE SPATIAL DISTRIBUTION OF COSMIC RAYS BEHIND THE INTERPLANETARY SHOCK—GLOBAL MUON DETECTOR NETWORK OBSERVATIONS
- Department of Physics, Shinshu University, Matsumoto, Nagano 390-8621 (Japan)
- Graduate School of Science, Chiba University, Chiba City, Chiba 263-8522 (Japan)
- National Institute for Space Research (INPE), 12227-010 São José dos Campos, SP (Brazil)
- Southern Regional Space Research Center (CRS/INPE), P.O. Box 5021, 97110-970, Santa Maria, RS (Brazil)
- Physics Department, Kuwait University, P.O. Box 5969 Safat, 13060 (Kuwait)
- School of Physical Sciences, University of Tasmania, Hobart, Tasmania 7001 (Australia)
- Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
- Department of Natural Sciences, College of Health Sciences, Public Authority of Applied Education and Training, Kuwait City 72853 (Kuwait)
We analyze the galactic cosmic ray (GCR) density and its spatial gradient in Forbush Decreases (FDs) observed with the Global Muon Detector Network (GMDN) and neutron monitors (NMs). By superposing the GCR density and density gradient observed in FDs following 45 interplanetary shocks (IP-shocks), each associated with an identified eruption on the Sun, we infer the average spatial distribution of GCRs behind IP-shocks. We find two distinct modulations of GCR density in FDs, one in the magnetic sheath and the other in the coronal mass ejection (CME) behind the sheath. The density modulation in the sheath is dominant in the western flank of the shock, while the modulation in the CME ejecta stands out in the eastern flank. This east–west asymmetry is more prominent in GMDN data responding to ∼60 GV GCRs than in NM data responding to ∼10 GV GCRs, because of the softer rigidity spectrum of the modulation in the CME ejecta than in the sheath. The geocentric solar ecliptic- y component of the density gradient, G {sub y}, shows a negative (positive) enhancement in FDs caused by the eastern (western) eruptions, while G {sub z} shows a negative (positive) enhancement in FDs caused by the northern (southern) eruptions. This implies that the GCR density minimum is located behind the central flank of IP-shocks and propagating radially outward from the location of the solar eruption. We also confirmed that the average G {sub z} changes its sign above and below the heliospheric current sheet, in accord with the prediction of the drift model for the large-scale GCR transport in the heliosphere.
- OSTI ID:
- 22666106
- Journal Information:
- Astrophysical Journal, Vol. 825, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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