May 11 Tue 10:00～11:30 太陽系小天体セミナー / Solar System Minor Body Seminar zoom
May 12 Wed 15:00～16:00 ALMA-J seminar zoom
May 12 Wed 15:30～17:00 NAOJ Science Colloquium zoom
May 14 Fri 13:30～15:00 Solar and Space Plasma Seminar zoom
May 14 Fri 15:30～17:00 談話会 / NAOJSeminar zoom
詳細は以下をご覧下さい
5月11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：5月11日（火曜日）10時00分～11時30分
場所：zoom
講演者：佐藤幹哉
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
5月12日（水）
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2021 May 12, 15:30-17:00
Place：zoom
Speaker：Salvatore Capozziello
Affiliation：University of Naples
Title：Cosmography as a tool to discriminate among cosmological models
Abstract：Cosmography is a model independent approach, useful to discriminate among concurring cosmological scenarios. After reviewing the main features and shortcomings of LCDM model, we propose a cosmographic approach, based on some polynomial series like Pade’, Chebyschev, etc. to investigate a dark energy and modified gravity. The main result is that series convergence seems a a powerful tool to extend the matching with the Hubble flow up to high redshift and then improve reliability of cosmological observations. A discussion on suitable datasets is also performed considering the role of observations at low and high redshift. In this perspective, combining data coming from SNeIa, GRBs, BAO, Galaxies and other cosmological distance indicators are crucial to achieve a self-consistent cosmological information at any scale.
Facilitator
-Name：Akimasa Kataoka
Comment：English
5月12日（水）
Campus: Mitaka
Seminar: ALMA-J seminar
Regularly Scheduled/Sporadic: Every Wednesday
Date and Time: 2021 May. 12 15:00-16:00
Place: Zoom
Speaker: Kosuke Namekata (NAOJ/JSPS fellow)
Title: Recent researches on stellar superflares with Kepler/Seimei telescope – toward the ALMA/ngVLA science –
Abstract:
Solar/stellar flares are explosive phenomena that release magnetic energy stored around sunspots/starspots. Solar flares often affect the Earth and planetary environment in the form of mass ejections and radiations. Recently, there has been a lot of interest in stellar `superflares’ (more than 10 times the energy of the largest solar flares) from the perspective of how superflares affect exoplanets and whether superflares occur on the Sun. Using data from the Kepler Space Telescope and the Kyoto University’s Seimei Telescope, we have been studying the mechanisms and properties of stellar superflares, especially on solar-type stars, and have found that many of them are the same as solar flares. Recently, we discovered for the first time the huge mass eruption associated with superflare on a solar-type star, and presented the observational evidence that mass ejections may have an impact on the planetary environment. In the future, it is expected that research on the effects of primary stars on planets will be further accelerated, and research using not only visible but also X-ray/radio waves is necessary. Radio research not only has the potential to approach the unsolved particle acceleration mechanism associated with magnetic reconnection, but also has the potential to observe mass ejections and stellar winds, so there are high expectations for ALMA/ngVLA. In this presentation, I will review my research and future plan.
Facilitator: Yuichi Matsuda, Yusuke Miyamoto
5月14日（金）
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：14 May (Fri), 13:30-15:00
Place： zoom
Speaker：Takyoshi Oba
Affiliation： NAOJ
Title：Average structure of the gas convection in the solar photosphere
Abstract：
The solar granulation consists of highly time-dependent
structure of granules and intergranular lanes. The enormous budget of
its kinetic energy is partly transformed and used to drive various
magneto-hydrodynamic phenomena appeared in the photosphere, and even in
the upper atmospheres. Many efforts have been dedicated to characterize
its vertical- and horizontal flow structures of the granulation in
qualitative and quantitative ways. There are two issues; (1) amplitude
relation of upflow/downflow is contradict between observations and
theoretical calculations, and (2) spatial distribution of horizontal
flow is severely hindered. One of the causes of the two issues is
insufficient spatial-resolution in the current observational equipment
for diagnosing the granulation. We have developed our own deconvolution
algorithm that corrects for the instrumental scattered-light, improving
the image quality. The technique provides a relation of strong-downflow
and weak-upflow, which is fairly good agreement with the synthesized
granulation. Moreover, the technique successfully provides a spatial
distribution of horizontal flow, revealing that speed of horizontal flow
is fastest in intergranular lanes. In this talk, I would like to show
our progress in characterizing the vertical- and horizontal flow fields
in the photosphere, and also show my future study for understanding of
the convection-related phenomena in the solar atmosphere.
Facilitator
-Name：Munehito Shoda
5月14日（金）
Campus：Mitaka
Seminar：NAOJ Seminar
Regularly Scheduled/Sporadic：Scheduled
Date and time：2021 May 14, 16:00～17:00
Place：zoom
Speaker：生駒 大洋 / Ikoma, Masahiro
Affiliation：科学研究部 / Division of Science
Title：地球型水惑星の形成と進化と多様性：太陽系外惑星の大気観測時代に向けた理論予測
Abstract：
ケプラー宇宙望遠鏡等の太陽系外惑星サーベイによって、太陽系以外にも惑星系が普遍的に存在することが判明した．一方で、惑星の数や質量、成分、軌道周期等に関して惑星系が実に多様であることも明らかになった．それによって、太陽系の構造を説明するために開発された惑星系形成モデルに対して、近年、大幅な改良がなされてきた．こうしたなかで、太陽系外惑星観測はいよいよ地球型惑星等の小型惑星をターゲットとし、また、分光観測によって大気特性を制約する時代に入った．こうした動向の中で、ハビタブル惑星候補である地球型水惑星の形成と進化、さらに、気候の安定性をどう考えるべきか．また、2020年代の観測計画を通してどのように検証していくのか．我々の最近の理論研究とその検証に向けた計画について紹介する．
Facilitator
-Name：浜名 崇 / Hamana, Takashi