How's SC24 doing?
posted: November 13, 2014

We are now close to 6 years since solar cycle 24 (SC24) started the gradual climb towards its solar cycle maximum. Over the last year, solar activity was mostly elevated, with several X-class flares and large sunspot groups. As the sunspot activity varies from month to month, the monthly sunspot numbers are smoothed to get an idea of the overall evolution. It then appears, pending the smoothing formula used, that a solar cycle maximum occurred during the early spring months of 2014 (red curve in graph underneath).

This maximum is quite a bit higher than the one recorded late 2011, as many solar observers will certainly confirm. The 2014 smoothed maximum seems to be about 83, whereas the one in 2011 only reached 66. This figure of "83" is very close to the maximum sunspot number predicted by the international prediction panel back in 2008-2009 (see this web page). The recent maximum was mainly due to increased activity on the southern solar hemisphere (red curve in graph underneath), whereas high activity on the northern hemisphere (blue curve) was the cause of the 2011 maximum.

Many large sunspot groups have appeared during this cycle maximum, and –of course- the solar cycle is not finished yet! Underneath a few examples of big groups in SC24 producing at least one X-class ("eXtreme") flare. From left to right and from top to bottom: NOAA 1520 (July 2012), NOAA 1429 (March 2012), NOAA 1944 (January 2014), and of course NOAA 2192 (October 2014). So far, the largest X-class flare (X6.9 – image underneath) occurred on 9 August 2011 and was produced by NOAA 1263.

It does not happen very often that in a single month, the Sun produces more than 3 X-class flares. In fact, since measurements started in 1976, there have been only 71 such months – as can be seen from the yellow and red dots superposed on the smoothed sunspot number in graph underneath. Seven of those have occurred during the ongoing SC24, with the latest in October due to famous NOAA 2192 flaring activity (6 X-class flares). However, as one can see from graph underneath, no month with 10 or more X-class flares (red dots) has occurred so far this SC. The red dots in the graph underneath show that SC21 had 3 such months, SC22 two, and SC23 only one. Amazingly, that one was not related to one of the Halloween groups, but to sunspot group NOAA 0808 that appeared in September 2005.

Credits - Data and imagery were taken from SILSO, NOAA/NGDC, and SDO.