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● 날짜 : 2015년 3월 28일 (화요일)
● 시간 : 16시 30분
● 장소 : 천문대 영상실
● 강사 : Prof. Valery Nakariakov, KHU, Univ. of Warwick
Title : Quasi-periodic pulsations in solar and stellar flares as a tool for coronal seismology
Abstract :
Periodic and quasi-periodic variation or pulsations (QPP) of the electromagnetic emission generated in solar flares is observed in all bands, from radio to gamma-rays. Typical periods range from a fraction of a second to several minutes. Also, the amplitudes and the quality
of the oscillations are very different in different cases. Medium- period (> 1 s) and long-period (> 1 min) quasi-periodic pulsations have properties similar to the properties of magnetohydrodynamic (MHD) waves observed in the corona. QPP provide us with a promising basis for diagnostics of flaring plasmas by the method of MHD seismology. Moreover, recent ground-based and spaceborne telescopes, e.g. Kepler, allow us for the detection of QPP in stellar flares. We discuss the search for QPP in Kepler data and the analysis of light curves. In particular, the detection of multiple periodicities in stellar
superflares evidences in favour of MHD-wave based mechanisms for their excitation. Furthermore, the apparent similarity between the typical signatures of QPP in solar flares and superflares on sun-like stars suggest that they are produced by similar mechanisms, and hence is important for the assessment of the possibility of a superflare on the Sun.
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