SOHO/MDI - Debrecen Sunspot Data (SDD)

The same method is used as in the case of production of Debrecen Photoheliographic Data (DPD) sunspot catalogue, and the software of the DPD has been suitably modified in order to adapt to SOHO/MDI full-disk continuum (Ic) images. The SDD yields the position and area data of all observable sunspots on an about hourly basis (30 min =< t < day) of MDI observations as well as the digitized images of sunspot groups. The text files contain the sunspot data (see SDDformat.txt), and the images of the sunspot groups show the measured spots. The full-disk facular data have the same format as full-disk sunspot data, but umbral areas are obviously not measured for faculae, and the first column of magnetic data contains the LOS magnetic field value at the brightest pixel within the facular contour in the intensity image.

We use the Full Disk Continuum images (fd_Ic_01h) from the Hourly Data Sets (from High Rate Science) Level 1.8. In this data set there are observations with different time resolution (from one/day to one/min) in different time intervals. In the latest years usually there is one Ic image per hour but not in every hours. To get a data set with a more or less regular time resolution that contains the most available images we have decided to use one image/hour time resolution. The best available Ic image is chosen within the time interval (hour - 30 min, hour + 30 min) which is the closest to the center of the time interval. If there is no Ic image in a given interval, the gap is filled with a Full Disk Continuum filtergram image (fd_I0_01h) when it is available. The measured Ic and I0 images are also published in our FTP archive in the original form. File name convention: I_yyyymmdd_hhmmss. During the measuring process the selected full disk intensity images are enlarged (3x), filtered, corrected for limb darkening, and transformed to negative. If the P_ANGLE of the image is 180 degree then the processed image is rotated to the normal position, otherwise the image preserves its original orientation.

The large amount of the available magnetograms allows for us to choose the magnetogram closest in time to the Ic image, and determine the magnetic field of the spots. Mean values of the line-of-sight magnetic field are computed if Ic images and magnetograms are available within 50 min. The best available magnetograms closest in time to the intensity images are chosen from the merged data sets of Full Disk Magnetograms of the Hourly Data Sets (from High Rate Science) and Daily Data Sets (from Low Rate Science & Synoptic) Level 1.8 (fd_M_01h and fd_M_96m_01d). All the magnetograms used in the catalogue and are available on-line. File name convention: M_yyyymmdd_hhmmss.

The set of images contains the Ic images with the nearest magnetograms selected after using quality-filters and time sequence criteria. If an hourly data is missing, it means that there is no Ic observation within the given time interval, or the available Ic observation is not measurable (perfect), or there are no measurable Ic images and magnetograms available with less than 50 min time difference.

The full-disk version of the SDD catalogue (fdSDD) is based on the same hourly time resolution MDI observations, but the spots are numbered by the computer program on the basis of their longitude and they is not assigned to sunspot groups. In the fdSDD catalogue all sunspots have their area, position and magnetic field values similar to SDD sunspot group catalogue. In this case the "g" raws are sums over the whole disk, which have no real physical meaning, but these raws are remained unchanged to keep the format, and in this form they show the excess of one of the polarities of the line-of-sight magnetic field concentrated in spots.

The previous version of SDD was produced during the ESA-PECS project entitled "SOHO/VIRGO, MDI - DPD catalogue studies" (2004-2007). The data (oldSDD1996) and images (old1996jpg) for 1996 are still available as samples for the results of this project. The whole set of data is reprocessed during the SOTERIA project because the MDI magnetograms were recalibrated at the end of 2008.