Evolution of Sunspots and Their Effect on Solar Irradiance Variations

The goal of this paper is to examine the evolution of sunspots and their relation to solar irradiance variations based on the sunspot data archive of the Heliophysical Observatory of the Hungarian Academy of Sciences. Long-term full-disk white-light observations have been made at the Debrecen Heliophysical Observatory and its Gyula observing station. Using observations from other observatories when they are not availabe in this archive is being used to complete a sunspot catalogue as a continuation of the Greenwich Catalogue and to provide a homogeneuous data base of the area and position of sunspots covering a century long time interval. As part of the measurement process, the photoheliograms are digitized and resolved into a 8K×8K matrix, which allows to measure and catalogue the area and position of sunspots (both umbra and penumbra) with high accuracy. These sunspot data are published in the Debrecen Photoheliographic Data catalogue (DPD). Since 1996, the SOHO/MDI intensity images have also been processed and analyzed in the same way as the DPD images and these MDI sunspot area and position data are published in the SOHO/MDI -- Debrecen Data (SDD) catalogue. In addition to the MDI intensity images, the MDI magnetograms are used to gather information about the average magnetic field strength values and polarities of the investigated sunspot umbra and penumbra.Considering the availability of the high time cadence MDI observations, we are able to study the evolution of sunspots in detail. In this paper we concentrate on the time frame of 1996 to 1997, when individual sunspot groups can be well-separated and their effect on solar irradiance can be studied in detail.