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Sunspots:What is interesting?
Author(s) -
Stix M.
Publication year - 2002
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/1521-3994(200208)323:3/4<178::aid-asna178>3.0.co;2-e
Subject(s) - sunspot , dynamo , solar dynamo , convection zone , physics , convection , astrophysics , variation (astronomy) , dynamo theory , magnetic field , mechanics , quantum mechanics
There are two kinds of questions that must be asked in the context of sunspots: those concerning the 22‐year magnetic cycle, and those concerning individual spots. The magnetic cycle is probably the result of an α Ω dynamo, but the nature and the magnitude of the α coefficient is not clear. The shear layer at the base of the convection zone plays an essential role in dynamo models, but it is not clear whether there is sufficient shearing for an α Ω dynamo. Further, several mechanisms have been proposed that yield a butterfly diagram, and at least two ways are possible for the generation of longterm variation. Sunspots show an enigmatic variation of darkness during the cycle. Other questions concerning individual spots are: Are current sheets essential? Where in the spot do convective or fluting instabilities develop? How intense is the convective energy transport in the umbra? What is the best description of sunspot decay – diffusion over the whole spot, or erosion at the boundary? And why is the variation of the frequency of sunspots in phase with the global cyclic variation of the solar luminosity?