Type-II Bursts in Meter and Deca – Hectometer Wavelengths and Their Relation to Flares and CMEs: II

Abstract

A study of the relationship between 38 type-II bursts recorded in meter and deca-hectometer (hereinafter m and DH) wavelength range and the associated flares and CMEs observed during the years 2000 – 2005 was carried out by Prakash et al. (2009). These events were divided into two classes: i) Class I, representing events where DH-type-II bursts are not a continuation of m-type-II bursts and ii) Class II, where DH-type-II bursts are a continuation of m-type-II bursts. In the present work, we extend the analysis of this sample of 38 events in three different steps: i) statistical properties of m- and DH-type-II bursts; ii) analysis of time lags between onsets of flares and CMEs associated with type-II bursts; and iii) statistical properties and relation between flares and CMEs of Class I and Class II events. We found a significant difference between the properties of m- and DH-type-II bursts of Class I and Class II events. For example, there are significant differences in starting and ending frequencies, bandwidth and speed. From the time delay analysis, we found the following. i) In 64% of Class I events, flares start after the onset of CMEs and the remaining 36% of flares start before the onset of CMEs. On the other hand, in the case of Class II events, the values are 83% and 17%, respectively. ii) The difference between the mean values of delay between flare start and DH start has high statistical significance (probability P of null hypothesis <1%). The time delays between the start of m-type-II burst and the CME onset are considerably larger for Class I events (P=7%) than Class II events. iii) There are notable differences in: (a) delay between the flare and CME onset times (P<1%); (b) flare rise time of Class I and Class II events (P<5%). iv) While the flare rise time is well correlated with the lag between the flare start and the CME onset in Class I events, there is no such correlation for Class II events.