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Solar and Space Plasma (SSP) Seminar Archive


Nov 24 Wed 15:30~17:00  NAOJ Science Colloquium            zoom

Nov 26 Fri 13:30~15:00   Solar and Space Plasma Seminar            zoom



Seminar:NAOJ Science Colloquium
Regularly Scheduled/Sporadic:Every Wednesday
Date and time:2021 Nov. 24, 15:30-17:00
Speaker:Takemura Hideaki
Title:The possibility of core growth with mass accretion and the core mass calculation method for continuum observations
Abstract:Stars are formed in dense regions which are called dense cores in the molecular clouds. Thus, it is crucial to understand how dense cores form from parental molecular clouds to reveal star formation processes. Since the evolution process of a star strongly depends on the mass, the mass is one of the most important properties of a dense core as well. The mass functions of dense cores (CMFs), the mass spectrum of dense cores, are expected to have information of the core evolution and star formation processes. Many previous studies of CMFs toward nearby star-forming regions with single-dish telescopes have suggested that the CMFs resemble the stellar IMFs. However, top-heavy CMFs are reported from recent ALMA observations toward distant high-mass star-forming regions. Therefore, the processes that link CMF and IMF have not been revealed. In this presentation, I will discuss the possibility of core growth suggested from the comparison of CMF and IMF in the Orion Nebula Cluster region and the core mass calculation method for dust continuum observation of ALMA.

Speaker:Kashiwagi Raiga
Title:The Role of Filament-Filament Collision in Star Formation
Abstract:Filamentary structures are recognized as a fundamental component of interstellar molecular clouds in observations made by the Herschel satellite. In addition, most of the prestellar cores that will become protostars in the future have been found along gravitationally unstable filaments. Based on these observational results, the relationship between filaments and star formation has attracted much attention. Recently, some observations imply that star formation is caused by filament-filament collisions. However, theoretical predictions are still insufficient: how they will evolve and which physical parameters change their evolution. Thus, We are challenging the theoretical understanding of filament-filament collisions by using numerical calculation. In this seminar, I will report the first result of a 2d-hydrodynamical simulation that investigated evolutions of filament-filament collisions and what parameters controlled their evolution.

-Name:Akimasa Kataoka


Campus: Mitaka
Seminar: Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic: Scheduled
Date and time:26 November (Fri), 13:30-15:00
Place: zoom

-Name:Takayoshi oba
Comment:in English




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Oct 19 Tue 10:00~11:30  太陽系小天体セミナー / Solar System Minor Body Seminar zoom

Oct 20 Wed 15:30~17:00  NAOJ Science Colloquium      zoom

Oct 22 Thu 13:00~14:30   Solar and Space Plasma Seminar    zoom


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Oct 5 Tue 10:00~11:30  太陽系小天体セミナー / Solar System Minor Body Seminar zoom

Oct 6 Wed 15:30~17:00  NAOJ Science Colloquium      zoom

Oct 8 Fri 13:30~15:00  Solar and Space Plasma Seminar    zoom

Oct 8 Fri 16:00~17:00   談話会 / NAOJSeminar       zoom       


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Sep 21 Tue 10:00~11:30  太陽系小天体セミナー        zoom

Sep 24 Fri 13:30~15:00  Solar and Space Plasma Seminar    zoom 






Campus: Mitaka
Seminar: Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic: Scheduled
Date and time:24 September (Fri), 13:30-15:00
Place: zoom
Speaker:Daiki Yamasaki
Affiliation: Kyoto University
Title:Numerical modeling of three-dimensional coronal magnetic field in the flare-productive solar active region NOAA 12673

Solar flares are the rapid energy release in the solar outer atmosphere, solar corona. The energy source of the solar flares is widely considered as the magnetic energy accumulated in solar active regions (ARs). Due to the observational limitation, however, it is hard to obtain the coronal vector magnetic field, and thus, we cannot directly detect the formation process of the magnetic flux ropes (MFRs). Hence, it is helpful to understand the formation and the evolution of the flare-productive ARs that the numerical modeling of the three-dimensional coronal magnetic field using an observable photospheric vector magnetic field. In our study, we focus on the AR 12673, which has produced many M-class and several X-class flares, one of which being an X9.3 flare, which is recorded as the largest solar flare in solar cycle 24. We studied the evolution of the three-dimensional flare-productive magnetic field within AR 12673, using a time series of nonlinear force-free field extrapolations of every 12 hr from 2017 September 4 00:00 UT to 6 00:00 UT. Our analysis found that three MFRs formed by September 4, one of which produced the X9.3 flare on September 6. One MFR has positive magnetic twist, which is a different sign from the other two MFRs. Since the temporal evolution of the magnetic flux of the MFR accumulating the positive twist is consistent with the profile of the GOES X-ray flux well observed from September 4 to 6, we suggest that the formation of the MFR having the positive twist is closely related to the occurrence of the M-class flares, including an M5.5 flare. We further found a magnetic null in the magnetic field surrounding the MFRs, in particular above the MFR having positive twist before the M5.5 flare, which is the largest M-flare observed during this period. By comparing with Atmospheric Imaging Assembly 1600 Å images, we found that the footpoints of the overlying field lines are anchored to the area where the brightening was initially observed. Therefore, we suggest that reconnection induced by the torus instability of the positively twisted MFR at the null possibly drove the M5.5 flare. In my presentation, I would also like to discuss the difference of the CME association between two homologous M-class flares observed in the AR 12673.

-Name:Munehito Shoda
Comment:in English,


Sep 1 Wed 15:00~16:00   ALMA-J seminar         zoom

Sep 3 Fri 13:30~15:00   Solar and Space Plasma Seminar  zoom

Sep 3 Fri 14:00~15:00   Tea Talk    zoom

Sep 3 Fri 16:00~17:00   NAOJ Seminar      zoom       


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