Active region transient brightenings - A simultaneous view by SXT, EIT andTRACE

Citation
D. Berghmans et al., Active region transient brightenings - A simultaneous view by SXT, EIT andTRACE, ASTRON ASTR, 369(1), 2001, pp. 291-304
Citations number
44
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY AND ASTROPHYSICS
ISSN journal
00046361 → ACNP
Volume
369
Issue
1
Year of publication
2001
Pages
291 - 304
Database
ISI
SICI code
0004-6361(200104)369:1<291:ARTB-A>2.0.ZU;2-7
Abstract
This paper reports on a qualitative study on the weakest flarelike brighten ings in active region that can be observed with current coronal imagers. Sp ecificallly, we investigate the correspondence of the "active region transi ent brightenings" (ARTB) first observed almost a decade ago with SXT with s imilar brightenings in the EUV that are now observed by EIT and TRACE. For this goal, exceptionally high cadence image sequences were acquired of a sm all but rapidly evolving active region (NOAA 8218), simultaneously by SXT, EIT, and TRACE. Within the timeframe of this coordinated campaign, we detec ted 41 soft X-ray brightenings and 373 EUV brightenings. We find that the s trongest brightenings observed by EIT are indeed the EUV counterparts of th e ARTBs seen by SXT. Weaker brightenings seen by EIT often do not have an X -ray counterpart. Among the brightenings detected with SXT we discover a ne w subpopulation, consisting of events that brighten in soft X-rays only, at a footpoint of a pre-existing SXT loop shortly after an ARTE occurred at t he other footpoint. The propagation speed of the perturbation suggests an i nterpretation in terms of slow mode MHD waves.