MAKING SENSE OF SUNSPOT DECAY I: Parabolic Decay Law and Gnevyshev–Waldmeier Relation
نویسنده
چکیده
In a statistical study of the decay of individual sunspots based on DPR data we find that the mean instantaneous area decay rate is related to the spot radius r and the maximal radius r0 as D = CD r/r0, CD = 32.0±0.26MSH/day. This implies that sunspots on the mean follow a parabolic decay law; the traditional linear decay law is excluded by the data. The validity of the Gnevyshev–Waldmeier relationship between the maximal area A0 and lifetime T of a spot group, A0/T ≃ 10MSH/day, is also demonstrated for individual sunspots. No evidence is found for a supposed supergranular “quantization” of sunspot areas. Our results strongly support the recent turbulent erosion model of sunspot decay while all other models are excluded. Abbreviations: CM – central meridian; DPR – Debrecen Photoheliographic Results; GPR – Greenwich Photoheliographic Results; MSH – millionth solar hemisphere; MSHER – MSH equivalent radius
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