Does Local Structure Within Shock-sheath and Magnetic Cloud Affect Cosmic Ray Decrease?

Abstract

The sudden short duration decrease in cosmic ray flux is known as Forbush decrease which is mainly caused by interplanetary disturbances. Generally accepted view is that the first step of Forbush decrease is due to shock sheath and second step is due to Magnetic Cloud (MC) of Interplanetary Coronal Mass Ejection (ICME). However, there are few questions which needs detail investigation. (i) Does the complete (or part of) ICME shock or MC contribute in cosmic ray decrease? (ii) Is there any internal structure associated with the ICMEs shock/MC which precisely contribute in decrease? To address these questions we have studied a total of 18 large ($>=8\%$) Forbush decrease events and associated ICMEs. Majority of events shows multi-steps Forbush decrease profile. This leads into re-classification of Forbush decrease events depending upon the number of steps observed in their respective profile. The present study clearly indicates that not only broad regions (shock-sheath and MC) contribute to Forbush decrease but also localized structures within shock-sheath and MC have very much significant importance in Forbush decrease profile.

arXiv commentSolar Physics, 15 pages, 6 figures

References in corpus (8)

• Small-scale magnetic islands in the solar wind and their role in particle acceleration. Part 1: Dynamics of magnetic islands near the heliospheric current sheet
• Diffusion and drift of cosmic rays in highly turbulent magnetic fields
• High rigidity Forbush decreases: due to CMEs or shocks?
• Forbush decreases and turbulence levels at CME fronts
• Understanding Forbush decrease drivers based on shock-only and CME-only models using global signature of February 14, 1978 event
• Relative contribution of the magnetic field barrier and solar wind speed in ICME-associated Forbush decreases
• Presence of Turbulent and Ordered Local Structure within ICME shock-sheath and its Contribution in Forbush decrease
• Quantitative assessment of drivers of recent climate variability: An information theoretic approach

Cited by in corpus (4)

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• Torsional Alfven wave embedded ICME magnetic cloud and corresponding geomagnetic storm
• The first in-situ observation of torsional Alfven waves during the interaction of large-scale magnetic clouds
• Does the Alfvén wave disrupt the large-scale magnetic cloud structure?