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Coronal mass ejection – driven shocks and the associated sudden commencements/sudden impulses

Veenadhari, B. and Selvakumaran, R. and Singh, R. and Ajeet, K.M. and Gopalswamy, N. and Kumar, Sushil and Kikuchi, T. (2012) Coronal mass ejection – driven shocks and the associated sudden commencements/sudden impulses. Journal of Geophysical Research, 117 (A04210). pp. 1-11. ISSN 0148–0227

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Interplanetary (IP) shocks are mainly responsible for the sudden compression of the magnetosphere, causing storm sudden commencement (SC) and sudden impulses (SIs) which are detected by ground-based magnetometers. On the basis of the list of 222 IP shocks compiled by Gopalswamy et al. (2010), we have investigated the dependence of SC/SIs amplitudes on the speed of the coronal mass ejections (CMEs) that drive the shocks near the Sun as well as in the interplanetary medium. We find that about 91% of the IP shocks were associated with SC/SIs. The average speed of the SC/SI-associated CMEs is 1015 km/s, which is almost a factor of 2 higher than the general CME speed. When the shocks were grouped according to their ability to produce type II radio burst in the interplanetary medium, we find that the radio-loud (RL) shocks produce a much larger SC/SI amplitude (average �32 nT) compared to the radio-quiet (RQ) shocks (average �19 nT). Clearly, RL shocks are more effective in producing SC/SIs than the RQ shocks. We also divided the IP shocks according to the type of IP counterpart of interplanetary CMEs (ICMEs): magnetic clouds (MCs) and nonmagnetic clouds. We find that the MC-associated shock speeds are better correlated with SC/SI amplitudes than those associated with non-MC ejecta. The SC/SI amplitudes are also higher for MCs than ejecta. Our results show that RL and RQ type of shocks are important parameters in producing the SC/SI amplitude.

Item Type: Journal Article
Divisions: Faculty of Science, Technology and Environment (FSTE) > School of Engineering and Physics
Depositing User: Sushil Kumar
Date Deposited: 2012
Last Modified: 16 Jan 2017 03:00

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