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IJRSP Vol.40 [2011] >
IJRSP Vol.40(2) [April 2011] >
| Title: | Directional muon telescopes not useful for estimating the magnitudes of Forbush decreases and geomagnetic storms |
| Authors: | Kane, R P |
| Keywords: | Forbush decrease
Coronal mass ejection (CME)
Interplanetary coronal mass ejection (ICME)
Geomagnetic storms
Cosmic rays (CR)
Muon anisotropy |
| Issue Date: | Apr-2011 |
| Publisher: | NISCAIR-CSIR, India |
| PACS No.: | 96.60.ph; 96.50.Bh; 96.50.sh |
| Abstract: | When a coronal mass ejection (CME) escapes
from the Sun and spreads in interplanetary space as a blob (termed as
interplanetary CME, ICME), galactic cosmic rays (CR) passing through the same
get modulated and one can detect anisotropies in data of muon directional
telescopes located on the Earth. For 15 severe storms (Dst < -200 nT) during
solar cycle 23 (1996-2006), the hourly data for Nagoya muon directional
telescopes showed that for each one of these storms, there were anisotropies in
one or more of the 16 directional telescopes. The maximum magnitudes of the
anisotropies were ~1% or less and had reasonably good relationships
(correlation +0.75) with the magnitudes of the following Forbush decrease (FD)
in the muons in the vertical direction V (muon V) and also in CR neutron
monitor (NM) data at Climax,
Colorado, USA.
But a correlation of ~0.75 implies a variance explained (square of correlation)
of only ~55%, leaving ~45% as random component. With geomagnetic Dst(min), the
muon anisotropy magnitudes had a still lower correlation (+0.44±0.20), which would imply a variance explained of only ~20%, leaving
~80% as random component, resulting in regression prediction errors exceeding
50%. Thus, the anisotropies were only a rough indicator of there being some
anomalous structure out in the interplanetary space, but the magnitudes of the
anisotropies could not give any accurate indication of the magnitudes of the
Forbush decreases that may follow, much less for the magnitudes of the
geomagnetic storm Dst(min) that may follow. |
| Page(s): | 76-84 |
| CC License: |  CC Attribution-Noncommercial-No Derivative Works 2.5 India |
| ISSN: | 0975-105X (Online); 0367-8393 (Print) |
| Source: | IJRSP Vol.40(2) [April 2011]
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