March 18 Mon 15:00-16:30
Solar and Space Plasma Seminar
hybrid; Insei Seminar Room in Subaru Building and Zoom
March 19 Tue 10:00-11:30
太陽系小天体セミナー
Zoom
March 22 Fri 16:00-17:00
NAOJ Seminar
hybrid; Large Seminar Room in Subaru Building and Zoom
詳細は下記からご覧ください。
=============== March 18 Mon===============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：18 March (Mon), 15:00-16:30
Place： Insei Seminar Room and Zoom
Speaker：Mr. Takero Yoshihisa
Affiliation：Kyoto University (M2)
Title： One-dimensaional MHD simulation for prominence formation triggered by single heating event
Abstract：
I will review on the thermal non-equilibrium phenomena in the solar atmosphere, and present on my master thesis.
Plasma condensation phenomena in the corona, such as prominences and coronal rain, have been observed for many years. It is not clear whether current models can explain their formation process. In one of the proposed models that explain observational properties, the “evaporation condensation” model, a steady or quasi-steady heating at footpoints of a loop drives dense plasma evaporation into the corona and triggers the condensation.
However, it is natural to think of such steady or quasi-steady heating as the superposition of multiple heating events occurring between multiple magnetic field lines. When studying physical processes along a single magnetic field line, a single heating event should be considered as the basic unit.
We therefore investigate whether condensation occurs when the non-steady single heating event occurs at footpoints of a coronal loop. For this purpose, we set a dipped loop and solve 1.5-dimensional (one-dimensional three-vector components) magnetohydrodynamic equations, including radiative cooling, thermal conduction, gravity, and phenomenological turbulence heating. After reproducing the corona by energy input from imposed velocity perturbation at the footpoints, prominence formation is investigated by adding artificial transient localized heating. It is found that required amount of the heating per unit of time is ∼ 10^3 times larger than in steady cases. The amount of energy reaches nanoflare class. We also perform a parameter survey varying the magnitude of the localized heating rate to investigate the conditions for condensation by transient localized heating. The results show that with sufficiently strong heating, sufficient plasma is supplied to the corona to allow cooling to proceed and condensation to occur. It is essential that the loop temperature decreases and thermal conduction becomes inefficient with respect to cooling. Using the loop length L and the Field length λF, the condition for condensation is expressed as λF ≲L/2 under conditions where cooling exceeds heating.
Facilitator
-Name：Akiko Tei
Comment：Japanese (Slides will be in English)
=============== March 19 Tue===============
キャンパス：三鷹
セミナー名：太陽系小天体セミナー
定例・臨時の別：定例
日時：3月19日（火曜日）10時00分～11時30分
場所：zoom
講演者：大坪貴文
世話人の連絡先
名前：渡部潤一
備考：テレビ会議またはスカイプによる参加も可
=============== March 22 Fri==============
Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Regular
Date and time：March 22, 2024 16:00-17:00
Place：Zoom/Large Seminar Room (hybrid)
Speaker：Director General, Dr. Saku Tsuneta
Affiliation：National Astronomical Observatory of Japan
Title：素晴らしく面白かった太陽の研究
＝40年の研究生活を振り返って＝
Abstract: これまで約40年近く、大学院生や仲間の研究者の方々と、「ひのとり」の硬Ｘ線望遠鏡、「ようこう」の軟Ｘ線望遠鏡、「ひので」の可視光望遠鏡といった飛び道具に載せる望遠鏡の開発を行ってきました。翔体実験装置の開発をするには、教科書を読むだけでは不十分で、観測装置の構想から設計、製作、試験、打上げ前不具合の徹底追及、そして打上げ、飛翔結果を解析して初めて一人前になれます。衛星実験では規模が大きく開発期間も長いため、この過程を経験することが難しく、衛星実験の合間にロケット実験や気球実験も行ってきました。
談話会では、プロジェクトの立ち上げ方や進め方について自分の経験をもとに論じるのと同時に、国立天文台での6年間について所感を述べたいと思います。
Facilitator
-Name：Fumitaka Nakamura