Solar Physics

, Volume 149, Issue 1, pp 23–29 | Cite as

A possible Coriolis-force contribution to the tilt-angle rotation of sunspot groups

  • Robert F. Howard


The rotation of the magnetic axes of sunspot groups is studied as a function of the expansion and contraction of the groups along their magnetic axes. In general, except for the extreme values of tilt-angle change, slow rates of rotation of the magnetic axes are associated with low values of expansion or contraction, and faster rotation of the magnetic axes is associated with rapid expansion or contraction. The direction of rotation of the magnetic axes is related to expansion or contraction in the sense that would be predicted by the Coriolis force. A comparison of the effect at high and low latitudes shows a difference that further supports the Coriolis force hypothesis, and an examination of the amplitude of the effect also suggests that the Coriolis force may be a factor in the tilt-angle rotation of spot groups.


Slow Rate Rapid Expansion Coriolis Force Sunspot Group Magnetic Axis 
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  1. Howard, R., Gilman, P. A., and Gilman, P. I.: 1984,Astrophys. J. 283, 373.Google Scholar
  2. Howard, R. F.: 1991,Solar Phys. 132, 257.Google Scholar

Copyright information

© Kluwer Academic Publishers 1994

Authors and Affiliations

  • Robert F. Howard
    • 1
  1. 1.National Solar ObservatoryNational Optical Astronomy ObservatoriesTucsonUSA

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