Three-minute Umbral Oscillations in Sunspots [태양흑점의 3분 암부진동]

Colloquium

Astronomy Colloquium (2019 Fall Semester)

* Date: Sept. 26
* Speaker: Prof. Jongchul Chae (SNU)
* Title: Three-minute Umbral Oscillations in Sunspots [태양흑점의 3분 암부진동]
* Abstract

Three-minute umbral oscillations represent the only known detectible MHD waves in sunspots — slow magnetoacoustic waves. They are important in the upper atmosphere because they nonlinearly develop and contribute to the heating and accceleration of plasma there. They are also useful in the investigation of the interior and the low atmosphere because they
carry informtion on the source region in the interior as well as the atmosphere through which they propagate.

We studied the physical properties and investigated their origin, based on the high resoution imaging spectral data taken by the Fast Imaging Solar Spectrograph of the Goode Solar Telescope, and the analytical solutions of acoustic waves in an atmosphere. As a result, we showed that the three-minute oscillations correspond to dispersive slow waves of frequencies just above the acoustic cutoff. Moreover, we found the observational results strongly suggesting that the three-minute oscillations are driven by the fast waves that are originally produced by impulsive disturbances in the interior like magnetoconvection events.
Finally, we propose that the single power peak of frequency just above the acoustic cutoff can be successfuly explained by the model of a photospheric resonator formed between the driving location and the temperature minimum region. Our results paved the way not only for the further investigation of slow waves, but also for the future detection of fast waves and Alfven waves in the sunspot atmosphere.

Date	Speaker	Title	Remarks
Sept 04 (Wednesday)	Dr. Bomee Lee (Caltech)	Probing the nature of dark matter through measurements of galaxy shapes	Wednesday
Sept. 12	No Colloquium	추석연휴
Sept. 19.	권오철 작가님	우주에 대한 호기심이 영화가 되기 까지
Sept. 26	Prof. Jongchul Chae (SNU)	Three-minute Umbral Oscillations in Sunspots [태양흑점의 3분 암부진동]
Oct. 2	Dr. Jeongwoo Lee (New Jersey Institute of Technology/ ISS, Shandong Univ.)	EUV and Microwave Studies of a Circular-Ribbon Solar Flare	Wednesday
Oct. 10	Dr. Michiel van Noort (Max-Planck Institute for solar system research),	Image restoration of solar data using multi frame blind deconvolution
Oct. 17	No Colloquium	Korean Astronomical Society Meeting
Oct. 24	Dr. Jongwan Ko (KASI)	Finding the origin of intracluster light	Talk in Korean
Oct. 31	Dr. Bernd Husemann (MPIA)	Characterizing multi-phase gas outflows and their powering mechanism in nearby AGN
Nov. 7	Prof. Hirofumi NODA (OSAKA Univ.)	Structure and State Transition of Supermassive Black Hole Accretion Flow Studied by Multi-Wavelength Observations
Nov. 14	Dr. Jinhee Lee (Kyung Hee Univ.)	Introduction to nearby young stellar moving groups
Nov. 21	Dr. Nobuyuki Sakai (KASI)	Mapping the Milky Way with Astrometry
Nov. 28	박새별 (KAIST / 안테나뮤직)	예술과 과학의 상호작용- 문화기술(Culture Technology)의 이해와 가능성
Dec. 5	Dr. Do-Young Byun (KASI)	The Extended KVN Project	Talk in Korean
Dec. 27.	Prof. Paul Yun, NASA Solar System Ambassador	NASA Space Economy	11:00 AM

2019 Fall semester detail