აბასთუმნის ასტროფიზიკური ობსერვატორიის მეცნიერებმა, ელენე ფილიშვილმა და დავით ხუციშვილმა, ორშაბათს, 30 მარტს წაიკითხეს სემინარი (იხ. ლინკი) ლუვენის კათოლიკურ უნივერსიტეტში თემებზე :
Dynamics of the flaring active region AR 1429 on March 6, 2012 – by Elena Philishvili (Ilia State University, Georgia)
Using the multi-wavelength observations by SDO/AIA and SDO/HMI instruments of the Active Region (AR) NOAA 11429 during 12:23 UT-12:56 UT on March 6, 2012, we present the dynamics of flaring coronal magnetic loops. The observed dynamics is interpreted as possible evidence for the magnetic reconnection. Further, we have detected intensity changes along the coronal loop that led to magnetic reconnection. Along the magnetic loop with the length L ≈ 38 Mm and radius a ≈ 3 Mm have observed five bright blobs with diminishing propagating velocity. The distance between two neighboring blobs is estimated as ≈ 7 Mm . Based on the observations we present two different interpretations of the results. First, the observed bright features can be standing sausage modes and secondly bright blobs along the loop might be signature of highly twisted loop that could be subject to kink instability.
Quasi-periodic variations in Doppler velocities of Hα Spicules – by David Khutsishvili (Ivane Javakhishvili State University, Georgia)
Two series of spectral observations of spicules in Hα spectral line with high cadence equal to 4.5 s each at 5500 km height (about 7 arcsec) above the solar limb were obtained using 53-cm Lyot coronagraph of Abastumani Astrophysical Observatory (Georgia) on October 17, 2012 . The duration of each series was about 5.5 and 6 min consisting of 75 and 80 CCD spectral images correspondingly with dispersion equal to 0.96 Å/mm in the second order near 6000 Å. The line-of-sight Doppler velocities with standard error equal to ±0.3 km/s were measured for 34 spicules in total. The life times of almost all measured spicules were longer than 5 min, therefore they resemble the type I spicules. No short lived structures (similar to type II spicules) were identified in the observed spicules. The Doppler velocity time series were processed using Lomb Periodogram Algorithm revealing 4 types of dominating period intervals centered around: 254 s, 136 s, 94 s and 65 s having confidence levels over 95%. The oscillations with periods around 254 s seems to be caused by quasi-periodic rebound shocks after the propagation of photospheric pulses. The oscillations with periods around 136 s might be caused by the oscillation of spicules axis at the kink cut-off frequency in gravitationally stratified magnetic tubes. In this case, seismological estimations give the density scale height as ~380 – 540 km for the kink wave speed of 70 – 100 km/s in spicules. Shorter period oscillations are probably caused by propagating kink waves in spicules.