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Title: Relationship between Dst(min) magnitudes and characteristics of ICMEs
Authors: Kane, R P
Keywords: Interplanetary disturbance;Magnetic clouds;Ejecta;Shocks;Intense storms;Corotating interaction region (CIR);Interplanetary coronal mass ejections (ICME);Dst;Interplanetary magnetic field
Issue Date: Aug-2010
Publisher: CSIR
PACS No.: 96.50.Bh; 96.50.Uv;; 94.20.Vv
Abstract: All interplanetary disturbances having shocks and directed towards the Earth are geoeffective, giving at least a storm sudden commencement (SSC) and giving Dst depressions [Dst(min)] in a wide range -10 to -500 nT, actual magnitudes roughly proportional to the magnitudes of negative Bz(min) of interplanetary magnetic field. During 1965-1996, the ejecta and shock events not accompanied with magnetic clouds (MCs) had only ~17% intense storms [Dst(min) ≤-200 nT] but ejecta and shocks accompanied with magnetic clouds (MCs) had ~40% intense storms. For solar cycle 23, ejecta and shocks without MCs had only ~3% intense storms; but ejecta and shocks accompanied by MCs had 11% intense storms. Thus, events accompanied with MCs gave larger percentage of intense storms. Events related to corotating interaction regions (CIRs) led to only weak and moderate storms [Dst(min): -20 nT to -140 nT]. For cycle 23, the plots of –Bz(min) vs –Dst(min) for ejecta and shocks without MCs showed a large scatter for the ranges Bz(min) -3 to -20 nT vs Dst(min) -5 to -170 nT. Thus, analysis in this region would give confusing and uncertain results. Concentrating on intense events [Dst (min) ≤ -200 nT], the Bz(min) vs Dst(min) plot showed a correlation of only +0.77±0.12, with considerable scatter in the Dst(min) range -200 to -300 nT [for the same value of Bz(min), Dst(min) would have an uncertainty of about ± 50 nT]. The correlation did not improve when Bz(min) was substituted by the product BzV, or by cumulative negative Bz from the start to the peak of negative Bz(min).
Page(s): 177-183
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.39(4) [August 2010]

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