Sunspot Group Development in High Temporal Resolution
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The Solar and Heliospheric Observatory/Michelson Doppler Imager – Debrecen Data (SDD) sunspot catalogue provides an opportunity to study the details and development of sunspot groups on a large statistical sample. In particular, the SDD data allow the differential study of the leading and following parts with a temporal resolution of 1.5 hours. In this study, we analyse the equilibrium distance of sunspot groups as well as the evolution of this distance over the lifetime of the groups and the shifts in longitude associated with these groups. We also study the asymmetry between the compactness of the leading and following parts, as well as the time profiles for the development of the area of sunspot groups. A logarithmic relationship has been found between the total area and the distance of leading–following parts of active regions (ARs) at the time of their maximum area. In the developing phase, the leading part moves forward; this is more noticeable in larger ARs. The leading part has a higher growth rate than the trailing part in most cases in the developing phase. The growth rates of the sunspot groups depend linearly on their maximum total umbral area. There is an asymmetry in compactness: the number of spots tends to be smaller, while their mean area is larger in the leading part at the maximum phase.
KeywordsSunspots Solar activity
The research leading to these results has received funding from the European Space Agency project, ESA PECS 98081. The results have been presented at the NSO Workshop 26, Sunspot, New Mexico, and JM wishes to acknowledge the support provided by the organisers. The authors are grateful to the unknown referee for the substantial improvement of the manuscript.