Polar surges and macrospicules: simultaneous H and He II 304 Å observations
A.A. Georgakilas 1,
S. Koutchmy 2 and
C.E. Alissandrakis 3
Received 6 April 1998 / Accepted 29 September 1998
We compare simultaneous sequences of H and He II 304 Å images near the solar limb. We propose to distinguish polar surges and giant spicules (macrospicules), among the He II structures observed beyond the solar limb. Polar surges have a complex structure when observed in H and an eruptive nature, reminiscent of normal surges in small scale. Giant spicules are simple spikes, very narrow compared to surges. They don't go as high as polar surges and apparently have shorter lifetimes. We found that most polar surges and giant spicules observed in He II are associated with H spikes; however there were cases without any corresponding H structure. Furthermore we observed H spikes that did not have He II counterparts. We analyze an example of a polar surge that appeared in He II well before its appearance in H and remained visible for a longer time. Most polar surges that we observed showed a similar behavior.
Key words: Sun: chromosphere Sun: transition region Sun: UV radiation
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© European Southern Observatory (ESO) 1999
Online publication: December 4, 1998