Regular solar observers have noticed that since mid-2016, the Sun has occasionally been devoid of sunspots. In fact, the month of December counted another 6 spotless days (see SDO-image from 10 December underneath). These spotless disks will gradually become a familiar feature as the solar cycle is heading for its next minimum, currently expected by the end of this decade. The number of spotless days can vary significantly from one solar cycle transit to another. For example, during the previous minimum (around 2008), no less than 817 spotless days were recorded, whereas the minimum period leading into solar cycle 23 (around 1996) counted only 309 such blemishless days.
As the current solar cycle 24 will gradually give way to the new solar cycle 25, several consecutive days and even weeks without sunspots will become the norm. In order to have an idea on the number of spotless days, and how these numbers compare to past solar cycles, the SILSO folks have created a “Spotless Days page”. This page contains graphs and tables on the accumulated number of spotless days, stretches of spotless days, and comparisons to other solar cycles – all supplemented with a word of explanation.
The previous minimum surprised scientists and solar observers by being the deepest in nearly 90 years. Will the upcoming solar cycle minimum show as many spotless days, or will solar cycle 25 take off much faster than expected? This “Spotless Days page” will provide you with a front-row seat on the current status of the solar cycle minimum and the number of spotless days. Enjoy!
Graph above shows the accumulated number of spotless days during the current solar cycle transition (green line), compared to the average of the solar cycles 16-23 (red line) and the solar cycles 10-15 and 24 (blue line). The dashed lines represent the resp. standard deviations. There are still many spotless days awaiting us...