Characteristics of DH type II bursts, CMEs and flares with respect to the acceleration of CMEs

Abstract

A detailed investigation on DH-type-II radio bursts recorded in Deca-Hectometer (hereinafter DH-type-II) wavelength range and their associated CMEs observed during the year 1997–2008 is presented. The sample of 212 DH-type-II associated with CMEs are classified into three populations: (i) Group I (43 events): DH-type-II associated CMEs are accelerating in the LASCO field view (a>15 m s−2); (ii) Group II (99 events): approximately constant velocity CMEs (−15<a<15 m s−2) and (iii) Group III (70 events): represents decelerating CMEs (a<−15 m s−2). Our study consists of three steps: (i) statistical properties of DH-type-II bursts of Group I, II and III events; (ii) analysis of time lags between onsets of flares and CMEs associated with DH-type-II bursts and (iii) statistical properties of flares and CMEs of Group I, II and III events. We found statistically significant differences between the properties of DH-type-II bursts of Group I, II and III events. The significance (Pa) is found using the one-way ANOVA-test to examine the differences between means of groups. For example, there is significant difference in the duration (Pa=5%), ending frequency (Pa=4%) and bandwidth (Pa=4%). The accelerating and decelerating CMEs have more kinetic energy than the constant speed CMEs. There is a significant difference between the nose height of CMEs at the end time of DH-type-IIs (Pa≪1%). From the time delay analysis, we found: (i) there is no significant difference in the delay (flare start—DH-type-II start and flare peak—DH-type-II start); (ii) small differences in the time delay between the CME onset and DH-type-II start, delay between the flare start and CME onset times. However, there are high significant differences in: flare duration (Pa=1%), flare rise time (Pa=0.5%), flare decay time (Pa=5%) and CMEs speed (Pa≪1%) of Group I, II and III events. The general LASCO CMEs have lower width and speeds when compared to the DH CMEs. It seems there is a strong relation between the kinetic energy of CMEs and DH-type-II properties.