Days without sunspots

Preliminary sunspot numbers by SILSO have indicated that the Sun was spotless on 30 July and on 7 and 8 August. Being already 19 months into the new solar cycle, this may come somewhat as a surprize, in particular because there have been already some episodes of increased solar activity with elevated sunspot numbers, such as late November last year and as recent as July this year. Nonetheless, spotless days can occur well after solar cycle minimum. For example, during the previous solar cycle, spotless days were not so rare late 2010, which was 2 years after cycle minimum. And during the onset of solar cycle 23, we still had 3 spotless days in January 1998, 17 months after cycle minimum. As SC25 progresses, the number of spotless days will further decrease. The evolution can be followed on SILSO's spotless days page at https://wwwbis.sidc.be/silso/spotless

 

The Sun on 28 November 2020 (left) and 30 July 2021 (right). Images by SDO/HMI.

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