Coronal Shocks of November 1997 Revisited: The CME-Type II Timing Problem
AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
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We re-examine observations bearing on the origin of metric type II bursts for six impulsive solar events in November 1997. Previous analyses of these events indicated that the metric type IIs were due to flares either blast waves or ejecta. Our point of departure was the study of Zhang et al. 2001 based on the Large Angle and Spectrometric Coronagraphs C1 instrument occulting disk at 1.1 Rsub-O that identified the rapid acceleration phase of coronal mass ejections CMEs with the rise phase of soft X-ray light curves of associated flares. We find that the inferred onset of rapid CME acceleration in each of the six cases occurred 1-3 min before the onset of metric type II emission, in contrast to the results of previous studies for certain of these events that obtained CME launch times 25-45 min earlier than type II onset. The removal of the CME-metric type II timing discrepancy in these events and, more generally, the identification of the onset of the rapid acceleration phase of CMEs with the flare impulsive phase undercuts a significant argument against CMEs as metric type II shock drivers. In general, the six events exhibited 1 ample evidence of dynamic behavior soft X-ray ejecta, extreme ultra-violet imaging telescope EIT dimming onsets, and wave initiation observed variously in H-alpha, EUV, and soft X-rays during the inferred fast acceleration phases of the CMEs, consistent with the cataclysmic disruption of the low solar atmosphere one would expect to be associated with a CME and 2 an organic relationship between EIT dimmings generally taken to be source regions of CMEs and EIT waves which are highly associated with metric type II bursts indicative of a CME-driver scenario.
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