Fig6_4 Winding up the field

Fig6_4 Winding up the field

Fig. 6.4 . A model for generating the changing location, orientation and polarity of the sunspot magnetic fields. Initially the magnetic field is supposed to be the dipolar or poloidal field seen at the poles of the Sun (left). The internal magnetic fields then run just below the photosphere from the Sunís south to north poles. As time proceeds, the highly conductive, rotating material inside the Sun carries the magnetic field along and winds it up. Because the equatorial regions rotate at a faster rate than the polar ones, the internal magnetic fields are stretched out and wrapped around the Sun's center, becoming concentrated and twisted together like ropes (middle and right). With increasing strength, the submerged magnetism becomes buoyant, rises and penetrates the visible solar disk, the photosphere, creating magnetic loops and bipolar sunspots that are formed in two belts, one each in the northern and southern hemisphere (right). [Adapted from Horace W. Babcock, The topology of the Sunís magnetic field, and the 27-year cycle, Astrophysical Journal 133, 572-587 (1961)]

Copyright 2010, Professor Kenneth R. Lang, Tufts University