talk: on Wednesday, March 29, 11am, Ariel house:
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CME Signatures Observed in Four SOHO/EIT Bandpasses
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Coronal Mass Ejections (CMEs) are traditionally observed by white-light
coronagraphs. However, ten years of SOHO observations have demonstrated that
EIT can well observe the initiation stage of at least the most of frontside
CMEs detected by LASCO. The restructuring of the corona above the limb allows
us to see even the origin of some of backside CMEs. ''CME Watch'' data series
(one image every 12 minutes) taken in any of the four EIT bandpasses is well
suited for detection of low corona CME counterparts. While the ''CME Watch''
series in the Fe XII bandpass are taken routinely, the observations with
similar cadence in other three bandpasses are made only occasionally. CME
signatures observed in the low corona by the EIT include: EUV dimmings, EIT
waves, prominence/filament eruptions, post-eruption arcades and a variety of
limb signatures. It is rare that a CME has all of these signatures.The
particulars of using each EIT bandpass for the CME detection are discussed.
Observations in the Fe XII bandpass seem to be optimal for the CME sources
identification. The Fe XV bandpass is less efficient due to the lower
signal-to-noise ratio. The Fe IX/X bandpass is also suitable. However,
significant transition region contribution to this bandpass makes the
identification of CMEs on-disc more difficult. The He II bandpass is less
convenient, although it also shows a variety of interesting events in
association with CMEs. It is shown that EUV dimmings are the most frequent
CME signatures. Some aspects of the nature of EIT waves and dimmings are
discussed.