ორშაბათს, 26 იანვარს აბასთუმნის ასტროფიზიკური ობსერვატორიის ახალგაზრდა თანამშრომლებმა, თამარ ჭაღიაშვილმა და ზურაბ ვაშალომიძემ წაიკითხეს მოხსენება ბელგიაში, ლუვენის კათოლიკური უნივერსიტეტის ფიზიკისა და მათემატიკის დეპარტამენტში ( KU Leuven, CmPA)
Abstract (by Tamar Chaghiashvili (Solar physics and Space weather group, Abastumani Astrophysical Observatory of Ilia State University, Georgia))
Solar flares are one of the most important events on the Sun, but their structure is still not understood well. We began our research for studying an emerging mechanism of solar flares and employed the Magnetograms of the flare corresponding active regions to see changes leading to plasma ejection. Data were taken from HMI and AIA on SDO satellite to follow the evolution of the well-developed sunspots of NOAA Active Regions 11158, 11166, 11429. Visual inspection of the imaging data showed morphological changes in magnetic field after the high-energy X and M flare eruptions; Soon, after flare-up, a small, dot-like brightening emerged in black and white parts of mapped magnetic field and disappeared few minutes before the flares ended. In this study, we discuss data of AR 11429 in detail. The active region appeared on March 2012 and hosted two high-energy X class flares. X 5.4 and X 1.3 flares break out in one hour interval
on March 7 with starting times 00:02 and 01:05 respectively. In the first occasion, the brightening cropped up in the black part of the mapped magnetic field, traversed the sunspot with average velocity 15 km/s and disappeared 7 minutes before the flare ended. In second case, the brightening began after a minute of flare start time, continued 11-13 minutes and ended 6 minutes before the flare end. Further investigation revealed the same brightening in 6 different layers in chromosphere and corona in AIA multiple wavelength data. We suggest, that detailed and long-termed analyze of changes in solar magnetic field will lead to better understanding of solar flares.
Abstract(by Zurab Vashalomidze (Solar physics and Space weather group, Abastumani Astrophysical Observatory of Ilia State University, Georgia))
The formation and dynamics of coronal rain, i.e. the fall of cool and dense blobs formed by thermal instability in the solar corona towards the solar surface with acceleration smaller than gravitational free fall, are not fully understood.The aim of this paper is to study the observational evidence of the formation of coronal rain blobs and to trace the detailed dynamics of individual blobs. We use time series of 171 Å, and 304 Å, spectral lines obtained by the Atmospheric Imaging Assembly (AIA) on board of the Solar Dynamic Observatory (SDO) above active region AR 11420 on February 22, 2012. Observations show that a coronal cloud disappeared in the 171 Å line and appeared in the 304 Å line over ~1 hour, which indicates a rapid cooling of the coronal cloud from 1 MK to 0.05 MK. An energy estimation shows that the radiation surmounts the heat input pointing out the process of “catastrophic cooling”. The cooling was accompanied by the formation of coronal rain below the cloud in the form of falling cold blobs. We studied two event: event 1 the detailed dynamics of three blobs and event 2 dynamics of two blobs falling along the line of motion. The mean velocities of the blobs were estimated: for the event 1 as 50 km s-1, 60 km s-1 and 40 kms-1 and for the event two as 102 km s-1 and 92 km s-1 . A polynomial fit shows the different values of the acceleration for different blobs, which are smaller than free-fall in the solar corona. The first and second blobs move along the same path, but with and without acceleration, correspondingly for the event 1. Numerical simulations show that the second blob moves in a stream of downflowing material caused by the first blob, therefore it has relatively high speed and no acceleration. For event 2 blobs first and second blobs move along the line motion, with acceleration which are smaller than free-fall. The formation of coronal rain blobs is probably connected to the process of “catastrophic cooling”. The different acceleration of different coronal rain blobs could be due to the different values of blob to corona density ratio. All blobs leave trails behind, which is currently unexplained.