The Ratio of the Areas of a Sunspot and Its Umbra: Two Populations of Sunspot Groups

Abstract

Greenwich type 0 sunspot groups, i.e., single sunspots, are considered. It is shown that in addition to the previously noted properties of sunspot groups separating into two populations, large long-lived (LLG) and small short-lived (SSG) ones, such groups, i.e., single sunspots, differ by the relationship between the total sunspot area \(S\) and the umbra area \(U\). The ratio \(S/U\) for the entire LLG population of this class may be deemed constant and is \(Q_{\textrm{LLG}}=5.756\pm 0.039\). The ratio of \(S\) and \(U\) for the SSG population is determined by a power law, \(S=(5.569\pm 0.093)U^{0.8957\pm 0.0040}\). The difference of the structural properties of sunspots in the populations, along with other previously found differences of their physical properties, is consistent with the hypothesis about the formation of the magnetic flux of two different sunspot populations in different zones: the deep tachocline and the near-surface leptocline.