Space Science & Space Physics Research Spotlight

What Causes Sunspot Pairs?

Analysis of magnetic fields on the Sun's surface offers a new clue on why sunspots appear.


Among the many scientific mysteries involving the Sun, scientists are still puzzled about the origins of sunspots: large regions of an extremely strong magnetic field that appear on the Sun’s surface. In 1981, a scientist observed that sunspots, which are generally seen in pairs, preferentially appear at the boundaries of unipolar magnetic (UM) regions—regions on the surface of the Sun that have rather weak magnetic networks of one polarity.

Akasofu offers evidence in support of this observation using solar magnetograms—“pictures” of the magnetic fields on the Sun’s surface. The author notes that there are many single spots (not in pairs) that cannot be explained by the present ideas on the formation of pairs of spots, which involve magnetic flux tubes rising from below the photosphere. He found that single spots of positive polarity tend to appear in a positive UM region, and single spots of negative polarity tend to appear in a negative UM region.

Using the above facts, a pair of spots can be explained if a positive single spot forms at the boundary of a positive UM region and induces a negative single spot in an adjacent negative UM region across the UM boundary.

The research shows that UM regions and their boundaries are essential in forming sunspot pairs and helps to better predict where on the solar disk sunspots will occur. The author also notes that because the incidence of sunspots is directly related to solar activity, UM regions may heavily influence space weather and the Sun-Earth connection. (Geophysical Research Letters, doi:10.1002/2014GL060319, 2014)

—JoAnna Wendel, Staff Writer

Citation: Wendel, J. (2015), What causes sunspot pairs?, Eos, 96, doi:10.1029/2015EO028347. Published on 5 May 2015.

© 2015. The authors. CC BY-NC 3.0