4月17日（火）13：30～15：00 太陽系小天体セミナー 南棟２階会議室
Apr 17 Tue Solar System Minor Body Seminar Conference Room, South Bldg.2F
4月17日（火）13：30～14：30 理論コロキウム 講義室
Apr 17 Tue DTA colloquium Lecture-room
4月20日（金）16：00～17：00 国立天文台談話会 大セミナー室
Apr 20 Fri NAOJ Seminar Large Seminar Room
詳細は以下をご覧下さい。
4月17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
- 4月17日（火曜日）13時30分～15時
- 場所
- 南棟２階会議室
- 講演者
- 大坪貴文
- 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
4月17日（火）
- Campus
- Mitaka
- Seminar
- DTA colloquium
Regularly Scheduled - Date and time
- April 17, 2017, 13:30-14:30
- Place
- Lecture room
- Speaker
- Yoshiaki Kato
- Affiliation
- Riken
- Title
- Radiation MHD Simulations of Waves and Vortices on the Sun and beyond
- Abstract
-
One of the long-standing problems in solar physics is to understand a
mechanism which maintains the solar atmosphere. The chromosphere, a
layer between the photosphere and the corona, is a key to unveiling
the mystery of the solar atmosphere. It is yet to be revealed
entirely by observations because the chromosphere has complex
structure and rapid variability. Therefore, radiation
magnetohydrodynamic (RMHD) simulations play a major role for
understanding such a complexity, which is difficult to interpret
physical processes.
I introduce my recent publications on the effect of MHD waves
associated with an isolated magnetic flux concentration (or a flux
tube), which is anchored in the photosphere and extended over the
corona. This is a classical problem which is extensively discussed in
many literatures and probably the best example to understanding MHD
waves. While all studies so far relied on inflicting driving forces
in the photosphere, only a self-consistent RMHD simulation of the
solar atmospheric layers from the surface convection zone to the
corona can resolve the realistic nature of MHD waves.
First, I present the generation and propagation of mostly slow mode
waves, driven by magneto-convective processes in the deep photosphere
and beneath it. This is so-called magnetic pumping process which
generates slow modes that propagate upward and develop into shock
waves in the chromosphere. The magnetic pumping is a robust mechanism
for generating shock waves in the vicinity of strong flux tube at the
chromospheric height and therefore it’s most likely to sustain the
chromosphere. Second, I present the identification of torsional waves
in the chromosphere and the corona. Vortical flows in the upper
convection zone and the photosphere force magnetic field structures to
rotate and thus produce so-called solar “magnetic tornadoes”, which
extend into the corona. Unlike slow modes, large portions of
torsional modes can reach the corona without suffering significant
dissipation and therefore it’s capable of sustaining the corona.
Third, I present the detection of physical phenomena in the flux tube
by magnetic pumping imprinted on the spectral lines. Thanks to the
rapidly advancing solar observations over the past decades, we will
have an unique opportunity to grasp the quantitative nature of MHD
waves in the near future. It will enable us to extend our knowledge
of plasma into those of the other astrophysical objects. Finally, I
will briefly talk about the future perspective on my research in the
next decades. - Facilitator
- -Name：Tomoya Takiwaki
- Comment
- in English
4月20日（金）
- キャンパス
- 三鷹
- セミナー名
- 談話会
- 定例・臨時の別
- 定例
- 日時
- ４月20日（金曜日）16時～17時
- 場所
- 大セミナー室
- 講演者
- 佐藤 真一
- 所属
- 国立情報学研究所
- タイトル
- 「画像認識の歴史と深層学習」
- Abstract
-
計算機による画像認識の研究は50年以上検討されているが、長らく顕著な進展
が見えなかった。それが、ここほんの数年で、特に深層学習の出現により、画
像認識の精度が大幅に向上し、様々な応用が検討されるようになってきた。本
講演では、画像認識研究の歴史と深層学習の出現を振り返り、できるようになっ
たこと、まだできないこと、新たに発生した問題等について議論したい。 - 連絡先
- -名前：矢野太平