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2019.3.4-3.10

3月5日(火)13:30~14:30  理論コロキウム 講義室
Mar 5 Tue        DTA colloquium  Lecture Room

3月5日(火)13:30~15:00  太陽系小天体セミナー  南棟2階会議室  
Mar 5 Tue        Solar System Minor Body Seminar  Conference Room, South Bldg.2F

3月8日(金)13:30~15:00  太陽天体プラズマセミナー  院生セミナー室
Mar 8 Fri      Solar and Space Plasma Seminar  Student Seminar Room

詳細は以下をご覧下さい。

3月5日(火)

Campus
Mitaka
Seminar
DTA colloquium
Regularly Scheduled/Sporadic
Regularly Scheduled

Date and time
March 5, 2019, 13:30-14:30
Place
Lecture room
Speaker
Scott Suriano
Affiliation
University of Tokyo
Title
The Formation of Rings and Gaps in Magnetized Wind-Launching Disks
Abstract
Radial substructures in circumstellar disks are now routinely detected by state-of-the-art observational facilities. There is also growing evidence that large-scale magnetic fields threading disks are responsible for launching disk winds and driving accretion. We investigate how rings and gaps form in magnetized disks through non-ideal MHD simulations. In axisymmetric 2D simulations including either Ohmic resistivity or ambipolar diffusion (AD), prominent features form in the disk surface density with a strong radial variation of the poloidal magnetic flux relative to the mass. Regions with low mass-to-flux ratios accrete quickly and lead to the development of gaps, whereas regions with higher mass-to-flux ratios accrete more slowly, allowing matter to accumulate and form dense rings. Specifically, in the AD-dominated disks, the radial variation of the magnetic flux is set by the reconnection of a highly elongated poloidal magnetic field across a thin midplane current sheet, through which fast laminar accretion occurs. We extend the simulations of AD-dominated disks to 3D and find that rings and gaps still develop naturally from the same basic mechanism that was identified in 2D. The rings and gaps remain stable in 3D for a few thousand orbital periods at the inner edge of the simulated disks, making them attractive sites for trapping large grains that would otherwise be lost to rapid inward radial migration.
Facilitator
-Name:Tomoya Takiwaki

Comment
in English

3月5日(火)

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5日(火曜日)13時30分~15時
場所
南棟2階会議室
講演者
石村周平
所属
茨城大学

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

3月8日(金)

Campus
Mitaka
Seminar
Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic
Regular
Date and time
8 March (Fri), 13:30-15:00
Place
Student Seminar Room, Subaru Bldg.
Speaker
Shin Toriumi
Affiliation
National Astronomical Observatory of Japan
Title
Five Years in NAOJ: How Far Have I Reached?
Abstract
The Sun is the only stellar object where we can observe a variety of plasma dynamics in the greatest detail, and this is why we solar physicists are fascinated. It harbors strong concentrations of magnetic field called sunspots, which are generated by the dynamo action in the solar interior and sometimes produce solar flares and CMEs. But it also shows much smaller-scale events such as Ellerman bombs and UV bursts, especially in the emerging flux regions. All these phenomena are now thought to be the manifestation of highly intricate coupling of plasma and magnetic field like the so-called magnetic reconnection. Utilizing this opportunity to give a talk in the SSP seminar, I will present my achievements in the last five years here in NAOJ. Starting from a brief introduction to several of my works before coming to NAOJ, I will focus on the three main topics that are closely related to the above intricate coupling, namely, the Hinode-IRIS-modeling study of sunspot light bridges, the statistical data analysis of flare-productive ARs, and the modeling attempt to reproduce these ARs. By the way, I have been sending the seminar abstracts since 2015 and I am just wondering how many actually read this. Finally, I will introduce the current projects including the review on the flaring ARs and show some perspectives of my future research.

Facilitator
-Name:Shin Toriumi

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