NOAA 3599's spectacular eruption

Active region NOAA 3599 had already rounded the Sun's southwest limb when it produced a long duration C-class flaring event. This event consisted of 3 individual flares which seemed to be part of one big ongoing magnetic restructuring near this active region. The event started at 00:59UTC and ended at 06:59 UTC, with a C1.9 flare peaking at 01:45UTC, a C4.9 at 04:05UTC, and a C6.0 flare peaking at 06:10UTC. The graph underneath shows the evolution in soft x-rays as recorded by GOES.


Extreme ultraviolet (EUV) images taken by the GOES/SUVI instrument showed the complexity of the eruption as it unfolded. The imagery underneath combines SUVI 171 (temperatures around 700.000 degrees) with SUVI 094 (multi-million degrees) filters, in respectively yellow-green and purple-pink colours. SUVI 171 gives a good view on the ejected magnetic structures, the magnetic restructuring and the series of post-eruption coronal loops ("arcade"). SUVI 094 gives a good view on the SADs, i.e. the supra-arcade downflows. More information on SADs can be found in the STCE newsitems here and here. Note the off-disk corona has been enhanced (SWHV), and the brief interruption in the clip is due to GOES "eclipse-season", i.e. the Earth passing briefly in between the Sun and GOES thus blocking GOES/SUVI's view of the Sun.


The EUV images clearly indicate material was ejected into space, and sure enough the coronagraphs on board SOHO showed an impressive partial halo coronal mass ejection (CME). It was mostly directed towards the west, and was -correctly- thought not to be directed towards the Earth in view of the position of the source region (behind the solar limb). Its plane-of-the-sky speed was around 750 km/s (CACTus). Nonetheless, a minor proton event was observed peaking on 16 March at 16 pfu (proton flux units). In the imagery underneath, the SOHO/LASCO coronagraphic images are overlaid on the SUVI 094 EUV image. The CME at the end of the clip moving southward is thought to have a farside source.




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