Home > Solar and Space Plasma (SSP) Seminar | 国立天文台談話会 | 太陽系小天体セミナー | 科学研究部コロキウム > 2021.10.4-2021.10.10


Oct 5 Tue 10:00~11:30  太陽系小天体セミナー / Solar System Minor Body Seminar zoom

Oct 6 Wed 15:30~17:00  NAOJ Science Colloquium      zoom

Oct 8 Fri 13:30~15:00  Solar and Space Plasma Seminar    zoom

Oct 8 Fri 16:00~17:00   談話会 / NAOJSeminar       zoom       






Seminar:NAOJ Science Colloquium
Regularly Scheduled/Sporadic:Every Wednesday
Date and time:2021 October 6, 15:30-17:00
Place:zoom / Instrument Development Bldg. 3 (hybrid)
Speaker:Doris Arzoumanian
Title:Star formation in filamentary molecular clouds
Abstract:Star formation is a multi-scale process, involving a complex interplay between turbulence, magnetic field, gravity, and feedback mechanisms, all of which vary in space and time.
I will summarise the main challenges in understanding the observed properties of star formation and present recent developments providing hints to address these questions, combining the results from observations and theoretical models.
In particular, I will discuss the star formation process in the context of the formation of filamentary molecular clouds and the role of filament merging and fragmentation in the formation process of stars from low to high masses.
-Name:Akimasa Kataoka


Campus: Mitaka
Seminar: Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic: Scheduled
Date and time:8 October (Fri), 13:30-15:00
Place: zoom
Speaker:Yuji Kotani
Affiliation: Kyoto University
Title:Theoretical and Observational Studies of Small-Scale Magnetic Reconnection on the Sun

Abstract:Small-scale magnetic reconnection frequently occurs in the solar atmosphere. The mechanism of these reconnections, and the associated behavior of the surrounding plasma, is a fundamental question in understanding the plasma in the solar and stellar atmospheres. In this seminar, I will introduce the following two topics that we have been working on regarding small-scale magnetic reconnection.
First, I will present a study of how the surrounding plasma behaves in association with the extremely small-scale magnetic reconnection expected to exist in the solar photosphere (Kotani & Shibata 2020). We tackled this problem by performing 3D MHD simulations in a high β setting similar to the solar photosphere, with the same magnetic field configuration and boundary conditions as in coronal jet simulations. As a result of the simulation, it was found that magnetic reconnection occurs in the high β environment as well as in the corona, and a jet-like structure is formed. We found that this jet-like structure is not formed by plasma flow but by the motion of compressed plasma accelerated perpendicular to the magnetic field lines by a shock wave. This shock is a slow shock formed by magnetic reconnection and propagated along the magnetic field lines. This result suggests that when magnetic reconnection occurs in a high β environment such as a solar photosphere, jet-like structures are formed, as in the case of the corona, but the formation mechanism is quite different.
Secondly, I will introduce my research on the scaling laws that attempt to unify the understanding of cold (chromospheric temperature) plasma eruptions with small-scale flares and filament eruptions and flares on the Sun (Kotani et al. in prep). We performed a statistical analysis of cold plasma eruptions with small flares in the quiet region captured by SMART/SDDI and SDO/AIA. First, we conducted cloud model fitting on the H-alpha spectra obtained by SMART/SDDI to obtain the ejecta’s line-of-sight velocity, mass, and kinetic energy. Next, we performed a DEM analysis on the SDO/AIA data to obtain the thermal energy of the small flare. From these data, we made a distribution map of the total flare energy and mass of the ejecta and confirmed that there was a positive correlation. To interpret this result theoretically, we assume that the cold plasma is a rectangular body supported by spiral magnetic field lines and derive a new scaling law for the mass of the ejecta and the total flare energy. As a result of the comparison between the scaling law and the observations, the cold plasma eruptions with small flares in the quiet region are in good agreement with the coronal field strength of 5 G in the scaling law. At the same time, the filament eruptions and flares are in good agreement with that of 5-50 G. We also compared the scaling law with observations that are thought to correspond to stellar filament eruptions and found that they are roughly consistent with the scaling law. These results quantitatively imply that the cold plasma eruptions with flares occurring at various scales are caused by the same physical mechanism via magnetic reconnection.

-Name:Takayoshi oba
Comment:in English


Seminar:NAOJ Seminar
Regularly Scheduled/Sporadic:Scheduled
Date and time:2021 October 8, 16:00~17:00
Speaker:播金優一/ Harikane Yuichi
Title:James Webb Space Telescopeの概要と期待される初期成果
James Webb Space Telescope (JWST) は2021年12月に打ち上げが予定されている、NASA/ESA/CSAによる赤外宇宙望遠鏡です。大口径を生かし赤外域で他の望遠鏡に比べて圧倒的な感度を達成し、初代銀河形成や星・惑星形成の現場を観測することを目標としています。JWSTではGuaranteed Time Observations (GTO), Early Release Science (ERS), General Observers (GO)の観測プログラムが予定されており、特にcycle-1 GOでは日本人研究者のプロポーザルも複数採択されています。本講演ではJWSTの概要と初期の観測計画、遠方銀河を中心に期待される成果を紹介いたします。

-Name:中村 文隆 / Nakamura, Fumitaka

Home > Solar and Space Plasma (SSP) Seminar | 国立天文台談話会 | 太陽系小天体セミナー | 科学研究部コロキウム > 2021.10.4-2021.10.10

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