ოთხშაბათს, 20 აგვისტოს, აბასთუმნის ასტროფიზიკური ობსერვატორიის თანამშრომლებმა და ილიას სახელმწიფო უნივერსიტეტის სტუდენტებმა ეკა გურგენაშვილმა და გულსუნ დუმბაძემ წაიკითხეს სემინარი ბელგიაში, ლუვენის კათოლიკურ უნივერსიტეტში, ფიზიკისა და მათემატიკის დეპარტამენტში (CmPA) თემაზე (იხ. ლინკი):

1) On the Dynamics of the Active Region Pattern: Method of Least-square Mapping on Second Order Curves

Abstract (by Gulsun Dumbadze (Ilia State University, Georgia))

Active Regions (ARs) are major source of various solar activity events. Development of the automated detection and identification of solar features has enormous necessity for understanding of the solar cycle.  We studied dynamics of two ARs: AR 11327 and AR 11726. In this work we developed novel method of automated AR border detection.  We build the AR boundary shape using least square method of fitting on the ellipse. After data processing we found that the semi-axes of ellipse and the inclination angle of the ellipse major semi-axis to solar equator oscillate. We have also detected that periods of oscillations of both semi-axes are the same (10.2 hrs) and the inclination angles oscillates with the characteristic periods 7.3 hours and 8.5 hours in these ARs, respectively. In both ARs we estimated the distribution of the Alfven speed value along the magnetic tubes (along two main spots) by interpreting the obtained oscillation of the inclination angle by the standing kink modes in thin tube approximation.

2) On Rieger type periodicity in the CME occurrence rates during solar cycle 24

Abstract (by Eka Gurgenashvili (Ilia State University, Georgia))

Rieger type periodicity was discovered 30 years ago, however, its  origin basic nature and dynamical properties are still unknown,  This work represents studies of periodicities in the occurrence rate of solar coronal mass ejections (CME), sunspot areas (SA) and solar flares and their comparison. Our main goals are the following: (i) To detect Rieger type periodicity in CME occurrence rates, (ii) compare it to characteristic periods in occurrence of the other magnetically driven processes and structures (solar flares, SA). (iii) find the character of temporal variation of Rieger periodicity during past few cycles. The Fourier analysis for both CMEs and flare ocurrence rates shows significant power corresponding to periods of 186 days. All periods in the Fourier spectra are obtained with larger than 99.5 % level of confidence. The wavelet analysis shows significant power at 195 days and 205 days in CME and flare occurrence rates, respectively.