3 X-class flares in NOAA 1890
posted: November 13, 2013

Last week, the Sun produced 3 X-class solar flares. "X" is short for "eXtreme", which means these flares are very strong. These X-class flares were produced by the complex and big sunspot group NOAA 1890. Pictures underneath were made by Belgian amateur solar observers on 9 November and give a good view on the extent and complexity of this sunspot group.

All 3 flares occurred in the trailing section of NOAA 1890, which contained a strong delta structure (see this STCE Newsletter for more information). The SDO/AIA 1700 images underneath provide an idea of the location of each flare. The three flares were very short-lived, each lasting 10 minutes or less. In this movie , the short-duration flares are seen as very brief light flashes in the trailing sunspots of NOAA 1890.

The image underneath provides another view on these flares. It is actually a combination image showing the X1.1 flare from 8 November as seen in extreme ultra-violet light (SDO/AIA 171) overlaid on a white light picture of the source sunspot group (SDO/HMI). Otherwise said, it combines a picture of the flare seen in the corona with a picture of the sunspot group seen in the photosphere (solar surface).

Though impulsive flares usually are not associated to coronal mass ejections (CMEs), these three flares seem to mark an exception. Most of the CMEs were directed southward, and no strong geomagnetic disturbance has been observed or is expected.

So far, there have been only 26 X-class flares during this solar cycle (SC24), 11 of which were produced this year. As can be seen in table underneath, the X3.3 flare was the third strongest of SC24. Nonetheless, this solar cycle has been lacking so far in truly strong flares (X10 or stronger). As this cycle maximum continues, more and potentially stronger flare events can be expected.

Credits - Data and imagery for the movie clips were taken from SDO and SOHO/LASCO.