In this thesis the search for any solar variable showing a cyclic behaviour in the Debrecen Photoheliographic Data (DPD) is presented. DPD is a detailed sunspot catalogue that has not been explored in this way before. The method used is to test parameters included, or calculated out of the given ones in the DPD and plotting the monthly averages with the standard error. Fluctuations present, reveal themselves as periodic curves.
In our analyses the umbra-penumbra area ratio is found to vary in a quasi- biennial manner. The amplitude of the periodicity decreases with increasing size of sunspots but seems to be independent of, e.g., the complexness and age of sunspot groups.
Periodicity analyses of the phenomenon show that the variation has a period that may vary from 1.5 to 3 years or more during the solar cycle.
Author: Szasz, Csilla
Source: Luleå University of Technology
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