ȥå   Խ ʬ Хåå ź ʣ ̾ѹ   ñ측 ǽ   إ   ǽRSS

Planet

Last-modified: 2023-05-30 () 09:52:00 (2d)
Top / Planet

Planet Seminar 2023

Planet seminar is held at 15:00 every Thursday (Organizers: Yuichi Ito, Kenji Furuya)
Planet journal clup is held at 12:00 every MondayOrganizers: Yuji Matsumoto, Kazumasa Ohno, Chanoul Seo

Schedule & History

FY2022 FY2021 FY2020 FY2019 FY2018 FY2017 FY2016 FY2015 FY2014

DateSpeakerTitleRemarksPerson in charge
4/4 15:00-15:30Shantanu Basu (University of Western Ontario)The Magnetic Field versus Density relation in Molecular CloudsFumitaka Nakamura
4/17 13:00-13:30Lizxandra Flores Rivera (University of Copenhagen)Gas dynamics and forbidden emission lines from outflows, jets, and disk winds in protoplanetary disksAkimasa Kataoka
4/17 13:30-14:00Marcelo Barraza-Alfaro (MIT)Predicting kinematical signatures of turbulence in ALMA high-resolution observations of CO rotational linesAkimasa Kataoka
4/18 11:00-11:30Raffaele Rani (ԢΩԻ)TBDKazunari Iwasaki
4/19 13:00-13:30Quentin Changeat (STScI)Exo-atmospheres in the era of JWST and ArielYuichi Ito
4/19 13:30-14:00Sushuang Ma (UCL)An Exoplanet Cloud Simulation and Retrieval PackageYuichi Ito
4/20 13:00-13:30Taichi Uyama (NAOJ/Caltech)Invitation to high-contrast hydrogen emission observations: detecting and characterizing accreting protoplanets in the context of planet formationYuka Fujii
4/20 13:30-14:00Dipen Sahu (Physical Research Laboratory)Density Structure of Centrally Condensed Prestellar Cores from Multi-scale ObservationsKenji Furuya
4/20 14:00-14:30Chen-Hau HsiehThe Evolution of Protostellar Outflow Cavities, Kinematics, and Angular Distribution of Momentum and Energy in Orion A: Evidence for Dynamical CoresFumitaka Nakamura
4/27 15:00-16:00Yuhiko Aoyama (̵)Type II planet-disk interaction in windy protoplanetary disksYuichi Ito
5/11 15:00-16:00Sho Shibata (University of Zurich)Accretion of refractory materials on forming hot-JupitersYuichi Ito
5/18 15:00-16:00Kazunari Iwasaki (NAOJ)A Constraint on the Amount of Hydrogen from the CO Chemistry in Debris DisksPaper introductionKenji Furuya
6/1 15:00-16:00Kanako Seki (The University of Tokyo)Effects of the planetary intrinsic magnetic field on the atmospheric escape and space environment around terrestrial planetsܸYuichi Ito
6/22 15:00-16:00Matías Gárate (MPIA)The synergy between photoevaporation, dead zones, and substructures can explain transition disks
4/4 Shantanu Basu (University of Western Ontario), The Magnetic Field versus Density relation in Molecular Clouds
I present recent three-dimensional nonideal MHD simulations of the evolution of the magnetic field strength versus density in turbulent magnetically-dominated clouds. The results show a natural transition from a relatively flat regime into a power-law regime that is approximately described by magnetic flux freezing. We develop an analytic model that matches the main features of the simulations, and shows that there is a natural transition density from the flat to the power law regime, and that it depends on the ambient Alfven Mach number. I also review some recent DCF observations of magnetic fields in dense star-forming regions and show that an apparent B-rho exponent of 2/3 can be understood in the context of strong magnetic fields, unlike some common interpretations of that exponent.
4/19 Quentin Changeat (STScI), Exo-atmospheres in the era of JWST and Ariel
For the last decade, exoplanet atmospheres have been observed from space using transits, eclipses and phase-curves with the Hubble and Spitzer Space Telescopes. About a hundred exoplanets were characterised, providing crutial clues about their nature and formation. However, due to the narrow wavelength coverage and low signal-to-noise, inference of complex properties at the population level have remained challenging. Promising higher quality data for thousands of exoplanets, the NASA/ESA/CSA-JWST and the ESA-Ariel missions mark the new era of exo-atmospheric characterization. In this presentation, we will discuss some of the observational constraints that can be obtained by this next generation of space telescopes as well as some of the challenges associated with the analysis of this new data.
4/19 Sushuang Ma (UCL), An Exoplanet Cloud Simulation and Retrieval Package
The existence of cloud has been prevalent in the transit study of exoplanetary atmospheres. However, the cloud models for transit spectroscopy from the last decade are waiting for optimisation for the data from the next-generation telescopes. Here we present YunMa, a cloud simulation and retrieval package for retrieval study of cloudy atmospheres of exoplanets in transit spectroscopy. It is integrated into TauREx retrieval platform and has a flexible API for taking cloud or haze models coded in Python. The current YunMa has an inbuilt Ackerman & Marley cloud microphysics model. We simulate the vertical cloud particle size distribution from cloud microphysics and further the cloud contribution in the radiative transfer. YunMa integrated in Taurex is capable of retrieving the cloud microphysics parameters and showed huge improvement in the retrieval performance compared with the grey cloud model which is commonly used in the last decade. YunMa is applied in the population study of different tiers in the Ariel Dry-Run to follow up the observation tier selection of Ariel targets to provide a better consideration of cloud impact on the selection strategy.
4/27 Yuhiko Aoyama (̵), Type II planet-disk interaction in windy protoplanetary disks
Recent studies have established magnetized disk winds as the primary mechanism driving accretion and evolution in protoplanetary disks, which can co-exist with turbulence from the magneto-rotational instability (MRI) in the outer disk. We conduct 3D global non-ideal magnetohydrodynamic (MHD) simulations of type-II planet-disk interaction that properly resolves the MRI turbulence and accommodates the MHD disk wind. We found that the planet triggers the poloidal magnetic flux concentration around its orbit, likely associated with spiral density shocks. The concentrated magnetic flux strongly enhances angular momentum removal in the gap region and alters the torque balance, making the planet-induced gap shape more similar to an inviscid disk, while being much deeper. The gap region is characterized by a fast trans-sonic accretion flow that is asymmetric in azimuth about the planet and lacks the horseshoe turns. The formation of a magnetized circumplanetary disk will also be discussed.
5/11 Sho Shibata (University of Zurich),Accretion of refractory materials on forming hot-Jupiters
The origin of Hot Jupiters is still unknown. These planets may have reached their observed short periods through disk migration or high-eccentricity migration. Each formation path is expected to lead to a different final planetary composition, especially in refractory to volatile ratio. In this talk, we compare solid accretion processes during disk migration and high-eccentricity migration. Using N-body simulations, we investigate the accretion rate of solid materials and the achieved refractory to volatile ratio in each formation pathway. Finally, we discuss how these results can be used to constrain the formation pathways of hot Jupiters.
6/1 Seki Kanako (University of Tokyo),Effects of the planetary intrinsic magnetic field on the atmospheric escape and space environment around terrestrial planets
Planets in the solar system are constantly exposed to supersonic plasma flows (solar wind) from the sun, and the interaction of the solar wind with planetary atmosphere and/or magnetic fields determines the space environment around the planets. This interaction is also closely related to atmospheric escape to space and in some cases, determines whether a terrestrial planet can retain its atmosphere, which is essential for surface habitable environment. Comparison between solar-system terrestrial planets has given as various insights about the problem. For example, understanding of atmospheric escape mechanisms to space is one of important problems to understand drastic climate change from a wet habitable environment to the dry current one in the ancient Mars. The geological studies suggest that the climate change occurred from 4 to 3.5 billion years (Ga) ago. It is known that the time period interestingly corresponds to the period just after the ancient Mars lost its global intrinsic field between 4 and 4.1 Ga ago. Observations by NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) have provided new insights about the atmospheric escape processes in operation at Mars. Among them, the cold ion escape is a promising candidate to enable a large number of heavy ions to escape from the ionosphere. In this presentation, an overview of the results of a statistical analysis of the ion composition measurements by MAVEN as well as global multi-species MHD simulations of solar wind-Mars interactions with a focus in effects of the intrinsic magnetic field will be presented. Based on these results, we will discuss the effects of the intrinsic magnetic field on the atmospheric escape from terrestrial planets. If the time permits, some application of our knowledge about the solar-system planets to terrestrial exoplanets will be also presented.
6/22 Matías Gárate (MPIA)
The synergy between photoevaporation, dead zones, and substructures can explain transition disks| There are many physical processes that are believed to shape the evolution of protoplanetary disks. Among them we can count the viscous spreading caused by the angular momentum redistribution, the dead zones in the inner disk where the turbulence is so low that stalls gas accretion, inside-outphotoevarative dispersal which is driven by the X-ray and UV radiation from the central star, and finally local substructures that can trap large amounts of dust during the early stages of disk evolution. All of these processes have been studied separately and can explain specific aspects of disk evolution, however it is not yet clear how they interact with each other when consider simultaneously. With this talk I show how the synergy between these ingredients can explain the puzzling properties of transition disks. In a hybrid model we find that early substructures take care of retaining the large amounts of dust that lead to the bright emission in the millimeter continuum seen in transition disks. The photoevaporative dispersal takes care of expanding a cavity to larger sizes, dragging all the accumulated material further and further from the star. And finally, dead zones allow to decouple the inner and outer outer regions during the dispersal process, which results in a long lived inner disk capable of sustaining the high accretion rates seen in these objects.