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● 날짜 : 2015년 6월 9일 (화요일)
● 시간 : 16시 30분
● 장소 : 천문대 영상실
● 강사 : Dr. T. Okamoto, Nagoya University
Title : High-resolution observations of the solar atmosphere and approach to the coronal heating
Abstract : Coronal heating and the acceleration of the solar wind are unsolved problems in solar physics.The propagation of Alfven waves along magnetic field lines is one of the candidate mechanismsto carry energy to large distances from the surface and heat the coronal plasma. Such kind ofwaves have been discovered in Hinode observations of prominences and spicules as small-scaletransverse oscillations of their fine structures since 2006. In cases of low frequency waves,the typical period and velocity amplitude of the waves are 2-5 minutes and 20 km/s,respectively, and they have enough power to heat the corona. on the other hand, high frequencywaves have periods of 50 seconds and velocity amplitudes of 8 km/s, and they are not soimportant in contribution to heating. It is no doubt that the solar atmosphere is filled with waves. The next approach is to findobservational evidence of wave dissipation. In 2013, the new satellite IRIS was launched toinvestigate chromospheric dynamics. With this instrument, we can obtain the physicalquantities of fine structures in such as prominences and spicules. We had collaborativeobservations of prominences with IRIS and Hinode, and found a signature of resonant absorption,which has been a ypothesized mechanism of wave dissipation for 40 years. The key observableis the phase difference between transverse oscillations by Hinode and line-of- sight velocities by IRIS in consideration of the opacity of the Mg II line.
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