Letter to the Editor
Long-term variation of sunspot latitudes
Pentti J. Pulkkinen 1,
John Brooke 2,3,
Jaan Pelt 4,5 and
Ilkka Tuominen 5
Received 5 November 1998 / Accepted 23 November 1998
We consider a continuous sunspot data set ranging from 1853 to 1996. The emphasis is given to long-term activity variations and north-south asymmetries. The difference of the distance between sunspot belts and equator between the northern and southern hemispheres is considered and a systematic variation is found. The period of this variation is about 8.4 sunspot cycles or about 90 years, and the amplitude is 1.3 degrees. This phenomenon could be explained by oscillation of a quadrupolar component of solar mixed parity mode magnetic field.
Key words: Sun: activity Sun: magnetic fields Sun: photosphere Sun: sunspots
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This article contains no SIMBAD objects.
© European Southern Observatory (ESO) 1999
Online publication: December 4, 1998