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HomeEducationalThe Sun and Solar ActivitySunspotsSequences of Spotless Days on the Sun Wednesday, Sep 24 2014 02:25 UT
The Sun and Solar Activity

Sequences of Spotless Days on the Sun

During solar minimum it is not unusual to see consecutive numbers of days where there no sunspots observed on the visible solar disc.

The table below compares observations since 1850.

Year of Sequence Number of Consecutve Spotless Days
191392
190169
187954
1855, 190249
187847
1878, 190245
191243
199642
185641
1901-0240
1924, 191339
1855-56, 1866-6738
1876, 187837
1933, 194436
186735
200932
1900, 1912, 1933-34, 200831

The table shows that the later solar minima, are still considerably shorter than some in the 19th and early 20th century in terms of consecutive spotless days. However, a note of caution is required because the coverage of observations was not nearly as good then as it is now. A sequence of spotless days can be broken by a single day on which a small spot appears. Lack of coverage by observations could therefore be very important in determining the length of such spotless sequences.

With the above qualification, the sequence in 1996 is still the longest observed in recent times during which good observations have been available.

Around solar maximum there will normally be few or no years where the visible disc of the Sun is spotless. The table below shows the total number of spotless days around each minima year. Again, use caution when considering the early data.

Year of Minimum Total Number of Spotless Days Around Minimum
1856647
1867406
18781028
1889756
1901938
19131015
1923532
1933570
1944269
1954446
1964227
1876272
1986273
1996306
2008815

It is interesting that there is a general trend for the number of spotless days to decrease when solar maximums are larger. With the increasing spotless days count, could we be heading towards a period of lower solar maxima?

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