Study of the Decay Rates of the Umbral Area of Sunspot Groups Using a High-resolution Database

Abstract

Abstract The emergence and decay of the sunspot groups are important components of the solar dynamo models. There are two different types of studies on the evolution of active regions. One of them is based on fewer data with higher spatial resolution, the other one uses more data with lower spatial resolution. The input data of the present study allow the investigation with high resolution both spatially and temporally. The temporal resolution of the Solar and Heliospheric Observatory Debrecen sunspot database is one and a half hours, and it also makes it possible to identify all individual sunspots with the position, area, and magnetic polarity. More than 200 sunspot groups have been selected, which have clear maxima on the solar disk, and the decrease of their umbral area is observable during at least four days. The decay rates were calculated by using two data: the umbral area and the number of contained sunspots—these decay rates were computed for the total umbral area of sunspot groups and their leading and following parts. The decay rate has a linear area dependency, and it is higher for the following part than for the leading one.