May 30 Tue 10:30-11:30 太陽系小天体セミナー Zoom
May 31 Wed 10:30-12:00 SOKENDAI Colloquium Zoom / the large seminar room (hybrid)
May 31 Wed 13:30-15:00 Solar and Space Plasma Seminar Zoom
May 31 Wed 15:30-17:00 NAOJ Science Colloquium Zoom / the large seminar room (hybrid)
詳細は下記からご覧ください。
=============== May 30 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：5月30日（火曜日）10時00分～11時30分
場所：zoom
講演者：鈴木文二
世話人の連絡先
名前：渡部潤一
=============== May 31 Wed===============
Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：May 31, 2023 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom
Speaker: Takumi Kakimoto
Affiliation: SOKENDAI 2nd year (M2) (Supervisor: Masayuki Tanaka, Daisuke Iono, Kiyoto Yabe)
Title: Spectroscopic observation of massive quiescent galaxy at z=4.53
Speaker : Itsuki Ogami
Affiliation: SOKENDAI 4th year (D2) (Supervisor: Wako Aoki, Hisanori Furusawa, Miho Ishigaki)
Title: Unveiling the NGC5466 tidal tail explored by the wide and deep HSC photometry
Facilitator
-Name：Matsuda, Graduate Student Affairs Unit
=============== May 31 Wed===============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：31st May (Wed), 13:30-15:00
Place： Zoom
Speaker：Yoshiki Hatta
Affiliation：Nagoya University / JSPS research fellow
Title：Noise estimation for travel time measurements in future solar polar missions
Abstract：Solar meridional circulation (MC) in the deep convection zone is a crucial component
for a better understanding of the solar dynamo mechanism.
This is the reason why there have been a number of local helioseismic studies
aiming at inferring the solar internal MC flow field.
However, the detection of the solar internal MC has been elusive
due to the fact that its signals are significantly smaller than the realization noise in travel time measurements
which originates from the stochastic nature of the turbulent convection.
In order to achieve the firm detection of the solar internal MC,
we are currently planning to propose a solar polar mission as a next-generation solar observation mission.
In this talk, I will give you a progress report on noise estimation in travel time measurements.
After I give you a brief introduction to the time-distance helioseismology
and present a motivation for the solar polar mission,
I show you to what extent we can reduce the realization noise in travel time measurements
by conducting the two-vantage-point observation of the Sun.
I also would like to discuss future prospects for assessing observational conditions required
to allow for travel time measurements with uncertainties small enough
for us to significantly detect the solar MC in the deep convection zone.
Facilitator
-Name：Takayoshi oba
Comment：in English
=============== May 31 Wed===============
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2023 May 31, 15:30-17:00
Place：zoom / the large seminar room (hybrid)
Speaker：Takeru Suzuki
Affiliation：The University of Tokyo
Title：MHD in a cylindrical shearing box
Abstract：By performing magnetohydrodynamical (MHD) simulations with weak
vertical magnetic fields in unstratified cylindrical and Cartesian
shearing boxes, we investigate basic properties of MHD turbulence
excited by magnetorotational instability. While both cylindrical and
Cartesian cases give a similar level of the time-averaged saturated
magnetic field strengths, the cylindrical setup exhibits extremely large
time-variability. Detailed analysis of the terms describing
magnetic-energy evolution with “triangle diagrams” surprisingly
reveals that in the cylindrical simulations, including a case with small
curvature, the compression of toroidal magnetic field is unexpectedly as
important as the winding due to differential rotation in the
amplification of the magnetic field, which is not seen in the Cartesian
simulation. This suggests that the physical properties of magnetic
evolution in the Cartesian shearing box simulation is fundamentally
different even from those in the nearly Cartesian simulation in the
cylindrical setup. In addition, the compressible amplification plays a
substantial role in triggering intermittent bursty enhancements in
magnetic energy observed in the cylindrical simulations. We discuss that
{\it the radial gradient of epicycle frequency}, which cannot be handled
in the normal Cartesian shearing box model, significantly contributes to
the bursty magnetic activity due to compressible amplification. We also
introduce a modified prescription for the cylindrical shearing boundary
condition.
Facilitator
-Name：Hiroki Nagakura
-Comment：English