Dec 12 Mon 15:30～17:00 Solar and Space Plasma Seminar Zoom
Dec 13 Tue 10:00～11:30 太陽系小天体セミナー Zoom
Dec 14 Wed 10:30～12:00 SOKENDAI Colloquium Zoom
Dec 14 Fri 15:30～17:00 NAOJ Science Colloquium Zoom / Instrument Development Bldg. 3
Dec 16 Fri 14:30～16:00 Solar and Space Plasma Seminar Zoom
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12月12日（月）
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：12th December (Mon), 15:30-17:00
Place： zoom
Speaker：Adur Pastor Yabar
Title : Stratified inversions of the solar photosphere: moving forward from hydrostatic equilibrium
Abstract:
The interpretation of solar spectropolarimetric observations are, arguably, the most insightful tool into the physical conditions of the solar atmosphere and specially the magnetic field that permeates it. This process relies on the assumption of some radiation- matter interaction model (radiative transfer equation ‒RTE) that, prescribed with some model parameters for the solar atmosphere, characterizes the outgoing radiation polarimetric properties. The inference of the model parameter from a set of observations is known as inversion, and some of the most advanced inversion codes (SIR, SPINOR, SNAPY, STiC, DESIRE, TIC) consider a thermodynamic and magnetic depth stratified atmosphere. An important issue that these inversion codes have to deal with is the fact that spectral lines are hardly sensitive to the gas pressure stratification, i.e. additional constraints are required in order to solve the thermodynamics of the atmospheric model. The most common one is to simplify the magneto-hydrodynamic (MHD) equation of motion to its simplest form, i.e., hydrostatic-equilibrium (HE), or consider only the term related to gravity. This approach leads to some limitations, among others, the inferred gas pressure stratification is as good as HE is representative of the real gas pressure and the physical properties of each pixel are retrieved independently of the neighbouring ones, i.e. there is no horizontal consistency.
Recently a variety of methods have been developed in order to deal with this limitation. One possibility that I will discuss in detail in this talk, is to use a less simplified MHD equation of motion than in HE. for instance by including the magnetic terms (the so-called magneto-hydrostatic approximation). In doing so, the inferred gas pressure is more consistent with the prediction from MHD and, for example, the Wilson-effect is retrieved in a consistent manner. In particular, I will consider the current status in the development of an spectropolarimetric inversion code (FIRTEZ-dz) that includes magneto-hydrostatic constraints in order to evaluate the gas pressure, validating its performance and application to real data.
Facilitator
-Name：Yusuke Kawabata
-Comment：in English,
12月13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：12月13日（火曜日）10時00分～11時30分
場所：zoom
講演者：吉川真
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
12月14日（水）
Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：December 14, 2022 10:30-12:00
Place：Zoom
Speaker : Takumi Kakimoto
Affiliation: SOKENDAI 1st year (m1) (Supervisor: Masayuki Tanaka, Daisuke Iono)
Title: Observations of Quenching Galaxies at High Redshifts (𝑧>4) and their properties
Speaker: Shubham Bhardwaj
Affiliation: SOKENDAI 3rd year (D1) (Supervisor: Maria Dainotti, Nozomu Tominaga, Kazunari Iwasaki)
Title: GRB Redshift Classification using Machine Learning
Facilitator
-Name：Matsuda, Graduate Student Affairs Unit
12月14日（水）
Campus：Mitaka
Seminar：NAOJ Science Colloquium
Regularly Scheduled/Sporadic：Every Wednesday
Date and time：2022 Dec. 14, 15:30-17:00
Place：zoom / Instrument Development Bldg. 3 (hybrid)
Speaker：Tadafumi Matsuno
Affiliation：University of Groningen
Title：Building blocks of the Milky Way revealed from the chemodynamics of halo stars
Abstract：Since galaxy merger and accretion are fundamental processes in galaxy evolution, reconstructing the accretion history is key to understanding the evolution of a galaxy. In the Milky Way, we can study ancient accretion events from kinematics and chemical abundances of halo stars. In this talk, I will first summarize the discovery of candidates for past galaxy accretions to the Milky Way, which are made from the analysis of stellar kinematics available thanks to the Gaia mission. I will then talk about our follow-up observation programs to chemically characterize their members, allowing us to confirm the accretion events and characterize the accreted galaxies’ properties. I will finally summarize the new opportunities that these found accreted galaxies bring to the study of nucleosynthesis processes.
Facilitator
-Name：Akimasa Kataoka
12月16日（金）
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：16th Dec (Fri), 14:30-16:00
Place： Zoom
Speaker：Kyuhyoun Cho
Affiliation：Lockheed Martin Solar & Astrophysics Laboratory
Title：Oscillations, waves, and convection inside sunspots
Recent observational studies suggested a possibility that small-scale magnetoconvection inside umbra may generate umbral oscillations. It is reported that the velocity oscillations inside the umbrae were spatially and temporally associated with active umbral dots, which is regarded as a manifestation of the small-scale magnetoconvection. It implies that the wave generations are closely connected to the magnetoconvection. In addition, propagations of the oscillation patterns tell us the depth of the wave source by modeling fast wave propagations. These studies give us hints about the subsurface structures of sunspots. I will present the spatial information of the source of the umbral oscillations and discuss their implication in the aspect of the magnetoconvection inside sunspots.
Facilitator
-Name：Takayoshi oba
-Comment：in English