Monthly sunspot number exceeds 100!

The provisional monthly International Sunspot Number for December 2022 reached a value of 113.1 (SILSO). For the ongoing solar cycle (SC25), this is the first time that a monthly sunspot number has exceeded the threshold of 100. The daily low was recorded on 1 December when the sunspot number was at 52 only, and the daily maximum sunspot number was recorded on 13 December when 158 was reached. Sunspot activity was dominated by the northern solar hemisphere for most of the month, except for the period from 11 till 21 December when most sunspots were observed on the southern hemisphere. This can be seen in the comparison imagery (SDO/HMI) underneath showing the Sun on 11 and 27 December.


The graph underneath shows that the previous solar cycle (SC24) had already reached higher monthly sunspot numbers than SC25 over the same 3-years period, i.e. 36 months counting from the smoothed solar cycle minimum. For SC24 and 25, that minimum took place respectively in December 2008 and December 2019 (month "0" in the graph). In fact, SC24 had just passed its first solar cycle maximum and was about to start a long stable period of nearly 18 months before resuming activity and reaching a second, higher maximum early 2014. Of note is that the most recent smoothed monthly sunspot numbers are slightly higher in SC25 than in SC24, i.e. respectively 81.0 in June 2022 vs. 77.2 in June 2011. This is most likely due to the enhanced solar activity during the first half of 2022, before a more or less stable period of about 5 months ensued with monthly sunspot numbers between 70 and 95.


The maximum of solar cycle 25 is still expected for 2024, and may possibly be higher than originally predicted (see the STCE's SC25 Tracking page). However, it remains to be seen if this will be a single maximum such as e.g. SC19, a clear double maximum such as e.g. in SC23 and SC24, or a broad cycle maximum with multiple maxima of nearly the same values such as during SC14 and SC16. The SILSO page at has graphs with the latest sunspot numbers as well as with some predictions of the smoothed monthly sunspot number for the next 12 months. These predictions get monthly updated as a new data point (monthly sunspot number) becomes available.




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