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Colloquium

First Spectroscopic Detection of Alfvenic MHD Waves in the Sunspot Chromosphere

2021-09-24
  • Speaker : 채종철 (서울대) / Jongchul Chae (SNU)
  • Date : 2021-09-29 10:30 ~ 11:30
  • Location : 온라인 진행 (Online)
  • Host : 임은경 / Eun Kyung Lim

Alfvén waves are considered to be physically important in understanding  physical processes in the solar corona such as nonthermal heating, solar wind acceleration and  the abundance enhancement of low first-ionization-potential elements.  However, it is still not clear how these waves are excited in the lower atmosphere. To reveal their physical origin,  we  have attempted to detect Alfvénic waves in the solar chromosphere using the spectroscopic method. By analyzing  the spectral data taken by the Fast Imaging Solar Spectrograph of the 1.6 meter Goode Solar Telescope, we successfully detected the Alfvénic waves in the  superpenumbral fibrils around a sunspot. This is the first spectroscopic detection of Alfvénic waves in the solar chromosphere. These waves are found to be physically associated with the three-minute umbral oscillation.  We conclude that the Alfvénic waves excited by the slow-to-Alfvén mode conversion may prevail in the solar chromosphere.