Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ap%26ss.tmp...75p&link_type=abstract
Astrophysics and Space Science, Online First
Astronomy and Astrophysics
Astrophysics
Sun, Coronal Mass Ejections, Solar Flares, Dh-Type-Ii Bursts
Scientific paper
A detailed analysis of characteristics of coronal mass ejections and flares associated with deca-hectometer wavelength type-II radio bursts (DH-CMEs and DH-flares) observed in the period 1997-2008 is presented. A sample of 62 limb events is divided into two populations known as after-flare CMEs (AF-CMEs) and before-flare CMEs (BF-CMEs) based on the relative timing of the flare and CME onsets. On average, AF-CMEs (1589 km s-1) have more speed than the BF-CMEs (1226 km s-1) and the difference between mean values are highly significant (P˜2%). The average CME nose height at the time of type-II start is at larger distance for AF-CMEs than the BF-CMEs (4.89 and 3.84 R o, respectively). We found a good anti-correlation for accelerating (R a=-0.89) and decelerating (R d=-0.78) AF-CMEs. In the case of decelerating BF-CMEs, the correlation seems to be similar to that for decelerating AF-CMEs (R d=-0.83). The number of decelerating AF-CMEs is 51% only; where as, the number of decelerating BF-CMEs is 83%. The flares associated with BF-CMEs have shorter rise and decay times than flares related to AF-CMEs. We found statistically significant differences between the two sets of associated DH-type-II bursts characteristics: starting frequency (P˜4%), drift rate (P˜1%), and ending frequency (P˜6%). The delay time analysis of DH-type-II start and flare onset times shows that the time lags are longer in AF-CME events than in BF-CME events (P≪1%). From the above results, the AF-CMEs which are associated with DH-type-II bursts are found to be more energetic, associated with long duration flares and DH-type-IIs of lower ending frequencies.
Prakash O.
Shanmugaraju Annamalai
Umapathy S.
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