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Studies of active region (AR) lifetimes are mostly restricted to short-lived ARs. The aim of this paper is to include recurrent ARs, which should be identified unambiguously. The first step is the algorithmic listing of possible returns; then, the candidates are visually checked using the unique HTML-feature of the Debrecen sunspot database. The final step is application of an asymmetric Gaussian function, introduced in previous articles, for short-lived ARs. This function has a surprisingly good fit to the data on correctly identified recurrent sunspot groups over several rotations enabling the reconstruction of the development on the far side of the sun. The Gnevyshev–Waldmeier rule for the area–lifetime relationship is not applicable for recurrent ARs; however, as a novel approach, a linear regression analysis extended to long lifetimes made it possible to recognize two populations of sizes for which two different area–lifetime relationships can be obtained. The lifetimes exhibit weak dependencies on the heliographic latitude and solar cycle phase. If an asymmetric Gaussian cannot be fit to the data, then they presumably belong to consecutive members of an active nest. [ABSTRACT FROM AUTHOR]

The primary task of the Debrecen Heliophysical Observatory (DHO) has been the most detailed, reliable, and precise documentation of the solar photospheric activity since 1958. This long-term effort resulted in various solar catalogs based on ground-based and space-borne observations. A series of sunspot databases and on-line tools were compiled at DHO: the Debrecen Photoheliographic Data (DPD, 1974 -), the dataset based on the Michelson Doppler Imager (MDI) of the Solar and Heliospheric Observatory (SOHO) called SOHO/MDI-Debrecen Data (SDD, 1996 - 2010), and the dataset based on the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO) called SDO/HMI-Debrecen Data (HMIDD, 2010 - ). User-friendly web-presentations and on-line tools were developed to visualize and search data. As a last step of the compilation, the revised version of Greenwich Photoheliographic Results (GPR, 1874 - 1976) catalog was converted to DPD format, and a homogeneous sunspot database covering more than 140 years was created. The database of images for the GPR era was completed with the full-disc drawings of the Hungarian historical observatories Ógyalla and Kalocsa (1872 - 1919) and with the polarity drawings of Mount Wilson Observatory. We describe the main characteristics of the available data and on-line tools. [ABSTRACT FROM AUTHOR]

The solar flare forecast techniques are usually based on magnetogram data, they mostly consider a solar active region as a whole and disregard its temporal variation. These techniques are also applicable to sunspot data but besides the global treatment the most detailed Debrecen sunspot databases make also possible to scrutinize the internal structure and dynamics of the solar active regions. This means the identification of the subdomains of strongest horizontal gradients of the magnetic field and to track them with a temporal resolution of 1.5 hours. The detailed data allow to make flare forecast for different time periods ahead, i.e. for the next couple of hours and days and with lower reliability for the next rotation. These procedures make possible a versatile system of flare forecast techniques. The program is supported by ESA. [ABSTRACT FROM AUTHOR]