A study of the relationship between 38 type-II bursts recorded in meter and decahectometer (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.
We have studied the characteristics of coronal mass ejections (CMEs) associated with Deca-Hectometric (DH) type II radio bursts (1-14 MHz) in the interplanetary medium during the year 1997-2005. The DH CMEs are divided into two parts: (i) DH CMEs (All) and (ii) DH CMEs (Limb). We found that 65% (177/273) of all events have the speed >900 km s −1 and the remaining 35% (96/273) events have the speed below 900 km s −1 . The average speed of all and limb DH CMEs are 1230 and 1288 km s −1 , respectively, which is nearly three times the average speed of general population of CMEs (473 km s −1 ). The average widths of all and limb DH CMEs are 105°and 106°, respectively, which is twice the average width (52°) of the general population of CMEs. We found a better correlation between the speed and width of limb DH CMEs (R = −0.61) than all DH CMEs (R = −0.53). Only 28% (177/637) of fast >900 km s −1 general population of CMEs are reported with DH type II bursts counterpart. The above results gives that the relation between the CME properties is better for limb events.
We have statistically analyzed a set of 115 low frequency (Deca-Hectometer wavelengths range) type II and type III bursts associated with major Solar Energetic Particle (SEP: E p > 10 MeV) events and their solar causes such as solar flares and coronal mass ejections (CMEs) observed from 1997 to 2014. We classified them into two sets of events based on the duration of the associated solar flares:75 impulsive flares (duration < 60 min) and 40 gradual flares (duration > 60 min).On an average, the peak flux (integrated flux) of impulsive flares X2.9 (0.32 J m −2) is stronger than that of gradual flares M6.8 (0.24 J m −2). We found that impulsive flare-associated CMEs are highly decelerated with larger initial acceleration and they achieved their peak speed at lower heights (-27.66 m s −2 and 14.23 R o) than the gradual flare-associated CMEs (6.26 m s −2 and 15.30 R o), even though both sets of events have similar sky-plane speed (space speed) within LASCO field of view. The impulsive flare-associated SEP events (Rt = 989.23 min: 2.86 days) are
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