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HomeEducationalThe Sun and Solar ActivitySunspotsSequences of Spotless Days on the Sun Sunday, Apr 20 2014 18:27 UT
The Sun and Solar Activity

Sequences of Spotless Days on the Sun

During September and October of 1996, we experienced a sequence of 37 days in a row during which there were no spots observed on the sun. This sequence is longer than any during recent solar minima - consistent which the current minimum being "deeper" than those during recent solar cycles.

But how does this sequence compare with historical sequences from the record of sunspot observations. The following table makes this comparison for observations since 1900 table.

Year of Sequence Number of Spotless Days
191392
190169
190249
190245
191243
1901-240
192439
191339
199637
193336
194436

The table shows that the 1996 sequence, whilst impressive, is still considerably shorter than some early in the century. However, a note of caution is required because the coverage of observations was not nearly as good early this century 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 the last 50 years during which good observations have been available.

Material prepared by Richard Thompson

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