15 X-flares for SC24
posted: Nov 2, 2012

On October 23, active region NOAA1598 produced the 15th X-class flare of the current solar cycle (SC). The X1.8 was of short duration, lasting only 8 minutes. It did not produce an energetic particle event (proton event), and there was no obvious indication of an ejected plasma cloud.


So far this solar cycle, GOES-data indicate there have been only 15 flares of the eXtreme class (X-type). Table underneath provides an overview of these flares, with a few characteristics such as in which sunspot group the flare took place, on which hemisphere, if there was a proton event associated with it, and if there was any geomagnetic effect from the ejected plasma cloud (See the NOAA data page for additional explanations). As one can see from this list, their influence has varied widely: from no impact at all, to a strong particle radiation event followed by severe geomagnetic storming. The difference in effects from these flares has various causes, such as the position of the source region on the solar disk, the orientation of the magnetic field of the ejected plasma cloud,...


The minimum of SC23-24 was in December 2008 when you take the monthly smoothed sunspot number as a reference (see SIDC). Solar cycle 24 is now 46 months old. Compared to previous cycles, the harvest of X-flares has been very meager. Indeed, over the same period, SC21 and 22 produced more than 3 resp. 5 times as many X-class solar flares. Even the much less active SC23 had nearly twice as many flares. But all three solar cycles produced at least half of their strong flares after solar cycle maximum. This would mean that most of SC24's firework is still to come!