Type II Radio Bursts with High and Low Starting Frequencies |
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Authors: | Annamalai Shanmugaraju Y-J Moon and Bojan Vrsnak |
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Institution: | (1) Department of Physics, Arul Anandar College, Karumathur, 625 514, Madurai, India;(2) Department of Astronomy and Space Science, Kyung Hee University, Yongin, 446-701, Korea;(3) Faculty of Geodesy, Hvar Observatory, Kaciceva 26, 10000 Zagreb, Croatia |
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Abstract: | We report on the detailed analysis of i) differences between the properties of type IIs with various starting frequencies (high: ≥100 MHz; low: ≤50 MHz; mid: 50 MHz
≤f≤ 100 MHz) and ii) the properties of CMEs and flares associated with them. For this study, we considered a sample of type II radio bursts observed
by Culgoora radio spectrograph from January 1998 to December 2000. The X-ray flares and CMEs associated with these events
are identified using GOES and SOHO/LASCO data. The secondary aim is to study the frequency dependence on other properties
of type IIs, flares, and CMEs. We found that the type IIs with high starting frequencies have larger drift rate, relative
drift rate, and shock speed than the type IIs with low starting frequencies. The flares associated with high frequency type
IIs are of impulsive in nature with shorter rise time, duration and delay between the flare start and type II start times
than the low frequency type IIs. There is a distinct power – law relationship between the flare parameters and the starting
frequencies of type II bursts, whereas the trend in the CME parameters shows low correlation. While the mean speed of CMEs
is larger for the mid-frequency group, it is nearly the same for the high and low frequency groups. On the other hand, the
percentage of CME association (90%) is larger for low frequency type IIs than for the high frequency type IIs (75%). |
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Keywords: | CMEs Flares Sun Radio bursts |
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