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Solar Physics

, Volume 176, Issue 2, pp 249–266 | Cite as

Making Sense of Sunspot Decay. I. Parabolic Decay Law and Gnevyshev–Waldmeier Relation

  • K. Petrovay
  • L. van Driel-Gesztelyi
Article

Abstract

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 ro and the maximum radius ro as D = CD r/ro, CD = 32.0±0.26 MSH day -1. 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 maximum area A 0 and lifetime T of a spot group, A0/T ≃10 MSH day-1, 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.

Keywords

Decay Rate Statistical Study Sunspot Area Maximum Area Erosion Model 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Kluwer Academic Publishers 1997

Authors and Affiliations

  • K. Petrovay
    • 1
  • L. van Driel-Gesztelyi
    • 2
    • 3
  1. 1.Instituto de Astrofísica de CanariasLa Laguna, TenerifeSpain
  2. 2.Observatoire de Paris, DASOPMeudon CedexFrance
  3. 3.Konkoly ObservatoryBudapestHungary

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