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Solar Seminar (13:30-15:00 Monday, Room 504 5th floor building NO.4) Access

Next presenters

Date	Time	Section	Speaker	File
11/11	13:30-15:00		Shirato	upload or download

Please upload your presentation file!!

Date	Section	Speaker	File
4/8		Asai	upload or download

For Speakers

Presentation time for speaker is: 60 minutes as a guide, and 30 minuites discussion.
(A speaker can use the full time of one seminar.)
Contents of talk are: :about your study
:review of recent interesting paper and share information of recent study of the Sun.
Language of slide and talks: Master cource students : Language of slide and talk could be Japanese
Doctor cource students and over : Slide must be English, and talking language could be Japanese
(If those who could not understand Japanese attend the seminar, it is preferable that you talk in English)
Title and Abstract: Please send the title and abstract of your presentation by the day before.
Presentation files: Please upload your presentation files by the start of the seminar.
If the presentation file has very large volume, please zip the file before uploading.
If you do not want to make public your unpublished results, please delete the relevant part before submission.

For Audiences

Honoring speakers: Plase clap your hands as a closure of a presentation to express your respection to a speaker.

For everyone

Publication sharing: Please send a copy of the submitted version of any paper on which they are working to the zasshikai mailing list just after submission

Useful webpage list for solar observers.

Date		Name	Title	Abstract	File
4/8		Asai	Solar Seminar 2024
4/15		Nagata	Near Infrared Tunable Filter for DIKIST		pptx 67.3 MB
4/22		Ishii	Filament eruptions and two ribbon flares at quiet regions	Today, I would like to introduce the following paper and SMART/SDDI observations of filament eruptions and two ribbon flares at quiet regions. A STUDY OF FAST FLARELESS CORONAL MASS EJECTIONS, H. Q. Song et al, 2013, ApJ, 773, 129.	pptx 10.5 MB
5/13		Mishra	Successive Emerging Flux Triggers Persistent Reconnection Jets in the Solar Atmosphere and Associated Heating	The dynamics of the solar atmosphere, including mass and energy circulation, coronal heating, and the initiation of eruptions both small and large, are governed by magnetic fields. High-resolution observational techniques and computational models are essential for unraveling these intricate phenomena. In my presentation, I will discuss how the successive emergence of magnetic flux influences various phases of jet activity in the solar atmosphere, contributing to the heating of the solar corona. Utilizing AIA multiwavelength imaging and SMART/SDDI spectroscopic observations, we categorized the observation period into three phases: initial, developing, and eruptive. The initial phase featured small-scale jets with velocities between 175-255 km/s. The developing phase was characterized by bidirectional plasma flows within the fan plane, while the eruptive phase saw three homologous jets within the fan-spine magnetic topology. We examined the topological alterations caused by magnetic reconnection and its persistent role in coronal heating. Differential Emission Measure (DEM) analysis indicated the existence of super-hot plasma, around 8-10 MK, which led to the ejection of hot and multithermal plasma into the overlying solar corona.	pptx 94.2 MB
5/20	@ Room 328	Dai	Simultaneous Horizontal and Vertical Oscillation of a Quiescent Filament Observed by CHASE and SDO	In this study, we present the imaging and spectroscopic observations of the simultaneous horizontal and vertical large-amplitude oscillation of a quiescent filament triggered by an extreme-ultraviolet (EUV) wave on 2022 October 2. Particularly, the filament oscillation involved winking phenomenon in H-alpha images and horizontal motions in EUV images. Here we focus on the EUV (Moreton) wave and the filament oscillation.	pdf 3.4 MB
6/3		Shirato	Overview of the IHOP 0473 observation using EIS/Hinode, IRIS and DST/Hida	Today I would like to talk about my rescent observation, through IHOPs (IRIS/Hinode Operations Plans) observation. This is a joint observation using IRIS, Hinode and other instruments. I conducted IHOP observation twice using Domeless Solar Telescope (DST) at Hida Observatory, on November 2023, and on April and May 2024. In today’s talk, I will provide an overview of these observations and the progress made so far, and the future plan.	pdf 18.1 MB
6/10		Otsu	Comparison of Sun-as-a-star and Spatially-resolved Velocity of Prominence Eruptions	Solar and stellar flares are explosive phenomena in atmospheres of the sun and cool stars. As known from imaging observations, solar flares are sometimes associated with filament/prominence eruptions which can lead to coronal mass ejections (CMEs). Such plasma eruptions and CMEs are thought to also accompany some stellar flares and affect exoplanet environments (e.g., Airapetian+ 2020). In stellar cases, Doppler shifted components observed in chromospheric lines such as H-alpha are often interpreted as plasma eruptions. Although most studies reported shifted components with velocities lower than the escape velocities of stars, some studies showed greatly high velocity components which can escape from stars and lead to CMEs (e.g., Inoue+ 2023). Also, some studies made direct comparison of stellar shifted components and solar H-alpha data of filament/prominence eruptions using Sun-as-a-star analyses, and confirmed their qualitative similarities (Namekata+ 2022, 2024, Leitzinger+ 2024). Thus, the existence of stellar plasma eruptions is becoming more certain. To clarify the quantitative relations between stellar activities and exoplanet environments, it’s required to investigate detailed dynamics of stellar plasma eruptions such as kinematic and thermal evolutions. In this study, I focused on kinematic evolution of plamsa eruptions in spatially integrated data. In order to clarify the relation between velocity distribution in resolved data and Sun-as-a-star velocity of plasma (prominence) eruptions, I conducted cloud model fitting for spatially resolved H-alpha data of SMART/SDDI and compare the fitting results with velocities obtained from Sun-as-a-star H-alpha spectra. I’d like to introduce some preliminary results and future plans.	pptx 9.9 MB
6/17		Shimada	Mean-Field Study of Stellar Activity-Rotation Relationship	This study explores the relationship between stellar surface magnetic fields and rotation rates. Previous observations (e.g., Wright+ 2011, 2018) have established a connection between stellar activity and rotation rates, with recent observations by Reiners (2022) indicating a parallel trend in surface magnetic fields. Observations suggest an anti-correlation between the magnetic field and Ro within the moderate Ro range (0.1 $<$ Ro $<$ 1), reaching saturation at extremely low Ro. Here, the Rossby number (Ro) is a crucial measure in assessing the impact of rotation on dynamics defined as the rotation period over convective turnover time. While global magnetohydrodynamic (MHD) simulations, such as those by Brun+ (2022), successfully replicate the anticorrelation in moderate Ro, the saturation phenomenon at extremely low Ro remains beyond the reach of current global simulations, and its driving mechanism remains unclear. To elucidate the saturation of the stellar magnetic field at extremely low Ro, We perform non-kinematic mean-field dynamo simulations by extending the solar case by Rempel (2006). Our findings reveal that the magnetic field strength is influenced by both stellar rotation rates and the assumed turbulent angular momentum (AM) transport process. Through detailed analysis, we demonstrate that the dependence of the magnetic field on Ro is intricately determined by the balance between AM transport by turbulence and the magnetic field. Notably, our results, in conjunction with recent insights into turbulence properties at low Ro (e.g. Kapyla 2024), align closely with observed magnetic field saturation patterns reported by Reiners (2022). We are also going to discuss the methods to justify the assumed turbulent effects.	pptx 9.9 MB
6/24		Yoshihisa	Non-thermal velocities in Corona and Coronal Rain	The coronal heating problem of why the corona reaches a million K relative to 6000 K at the photosphere is one of the key open questions in the stellar physics. From an observational perspective, non-thermal line broadening are observed and considered to be the indicator of heating properties. However, previous numerical simulations have not explained this observation. This work attempt to reproduce observed non-thermal vel. by taking into account turbulent heating. We also investigate the non-thermal vel. in the coronal rain.	pptx 12.9 MB
7/1		Kida	Canceled
7/8		Natsume	Comparison of multiple chromospheric lines for post-flare loop		pdf 3.3 MB
7/8	Guest Seminar 15:30-17:00	Prof. Petr Heinzel (Astronomical Institute, Czech Academy of Sciences and University of Wroclaw, Center of Excellence 'Solar and Stellar Activity')	Radiative transfer in solar prominences: A historical overview and current trends	Similarly as in other branches of solar atmospheric spectroscopy, development of the non-LTE (i.e. departures from Local Thermodynamic Equilibrium) physics and related numerical tools in 60-ties and 70-ties of the last century largely influenced also the prominence research. First 1D prominence models have been constructed showing the critical importance of an external illumination in the relevant spectral lines and continua. Later on the effects of 2D geometry and partial redistribution have been investigated and the modeling turned to problems of heterogeneous media, multithread structures and finally studies of the energy balance. In parallel, new multi-wavelength spectral data became available at higher spatial and temporal resolution. We will review the progress from 70-ties till now and finally summarise the current modern trends in numerical non-LTE radiative-transfer modeling, focusing on both quiescent as well as eruptive prominences. Namely the coupling of up-to-date MHD simulations with optically-thick radiative transfer will be highlighted.
7/22		Suzuki	Observation of M dwarf's magnetic fields	Understanding details of the stellar winds of M-type stars is important for study of exoplanetary atmospheres. In order to simulate stellar winds, knowledge of magnetic fields of M dwarfs is required as a numerical setup. Here, I will summarize observational studies of magnetic fields of M dwarfs. They clarified magnetic field strength and geometries.	pdf 1.0 MB

Date

Name

Title

Abstract

File

4/8

Asai

Solar Seminar 2024

4/15

Nagata

Near Infrared Tunable Filter for DIKIST

pptx
67.3 MB

4/22

Ishii

Filament eruptions and two ribbon flares at quiet regions

Today, I would like to introduce the following paper and SMART/SDDI observations of filament eruptions and two ribbon flares at quiet regions.
A STUDY OF FAST FLARELESS CORONAL MASS EJECTIONS, H. Q. Song et al, 2013, ApJ, 773, 129.

pptx
10.5 MB

5/13

Mishra

Successive Emerging Flux Triggers Persistent Reconnection Jets in the Solar Atmosphere and Associated Heating

The dynamics of the solar atmosphere, including mass and energy circulation, coronal heating, and the initiation of eruptions both small and large, are governed by magnetic fields. High-resolution observational techniques and computational models are essential for unraveling these intricate phenomena. In my presentation, I will discuss how the successive emergence of magnetic flux influences various phases of jet activity in the solar atmosphere, contributing to the heating of the solar corona. Utilizing AIA multiwavelength imaging and SMART/SDDI spectroscopic observations, we categorized the observation period into three phases: initial, developing, and eruptive. The initial phase featured small-scale jets with velocities between 175-255 km/s. The developing phase was characterized by bidirectional plasma flows within the fan plane, while the eruptive phase saw three homologous jets within the fan-spine magnetic topology. We examined the topological alterations caused by magnetic reconnection and its persistent role in coronal heating. Differential Emission Measure (DEM) analysis indicated the existence of super-hot plasma, around 8-10 MK, which led to the ejection of hot and multithermal plasma into the overlying solar corona.

pptx
94.2 MB

5/20

@ Room 328

Dai

Simultaneous Horizontal and Vertical Oscillation of a Quiescent Filament Observed by CHASE and SDO

In this study, we present the imaging and spectroscopic observations of the simultaneous horizontal and vertical large-amplitude oscillation of a quiescent filament triggered by an extreme-ultraviolet (EUV) wave on 2022 October 2. Particularly, the filament oscillation involved winking phenomenon in H-alpha images and horizontal motions in EUV images. Here we focus on the EUV (Moreton) wave and the filament oscillation.

pdf
3.4 MB

6/3

Shirato

Overview of the IHOP 0473 observation using EIS/Hinode, IRIS and DST/Hida

Today I would like to talk about my rescent observation, through IHOPs (IRIS/Hinode Operations Plans) observation. This is a joint observation using IRIS, Hinode and other instruments. I conducted IHOP observation twice using Domeless Solar Telescope (DST) at Hida Observatory, on November 2023, and on April and May 2024. In today’s talk, I will provide an overview of these observations and the progress made so far, and the future plan.

pdf
18.1 MB

6/10

Otsu

Comparison of Sun-as-a-star and Spatially-resolved Velocity of Prominence Eruptions

Solar and stellar flares are explosive phenomena in atmospheres of the sun and cool stars. As known from imaging observations, solar flares are sometimes associated with filament/prominence eruptions which can lead to coronal mass ejections (CMEs). Such plasma eruptions and CMEs are thought to also accompany some stellar flares and affect exoplanet environments (e.g., Airapetian+ 2020). In stellar cases, Doppler shifted components observed in chromospheric lines such as H-alpha are often interpreted as plasma eruptions. Although most studies reported shifted components with velocities lower than the escape velocities of stars, some studies showed greatly high velocity components which can escape from stars and lead to CMEs (e.g., Inoue+ 2023). Also, some studies made direct comparison of stellar shifted components and solar H-alpha data of filament/prominence eruptions using Sun-as-a-star analyses, and confirmed their qualitative similarities (Namekata+ 2022, 2024, Leitzinger+ 2024). Thus, the existence of stellar plasma eruptions is becoming more certain. To clarify the quantitative relations between stellar activities and exoplanet environments, it’s required to investigate detailed dynamics of stellar plasma eruptions such as kinematic and thermal evolutions. In this study, I focused on kinematic evolution of plamsa eruptions in spatially integrated data. In order to clarify the relation between velocity distribution in resolved data and Sun-as-a-star velocity of plasma (prominence) eruptions, I conducted cloud model fitting for spatially resolved H-alpha data of SMART/SDDI and compare the fitting results with velocities obtained from Sun-as-a-star H-alpha spectra. I’d like to introduce some preliminary results and future plans.

pptx
9.9 MB

6/17

Shimada

Mean-Field Study of Stellar Activity-Rotation Relationship

This study explores the relationship between stellar surface magnetic fields and rotation rates. Previous observations (e.g., Wright+ 2011, 2018) have established a connection between stellar activity and rotation rates, with recent observations by Reiners (2022) indicating a parallel trend in surface magnetic fields. Observations suggest an anti-correlation between the magnetic field and Ro within the moderate Ro range (0.1 $<$ Ro $<$ 1), reaching saturation at extremely low Ro. Here, the Rossby number (Ro) is a crucial measure in assessing the impact of rotation on dynamics defined as the rotation period over convective turnover time. While global magnetohydrodynamic (MHD) simulations, such as those by Brun+ (2022), successfully replicate the anticorrelation in moderate Ro, the saturation phenomenon at extremely low Ro remains beyond the reach of current global simulations, and its driving mechanism remains unclear. To elucidate the saturation of the stellar magnetic field at extremely low Ro, We perform non-kinematic mean-field dynamo simulations by extending the solar case by Rempel (2006). Our findings reveal that the magnetic field strength is influenced by both stellar rotation rates and the assumed turbulent angular momentum (AM) transport process. Through detailed analysis, we demonstrate that the dependence of the magnetic field on Ro is intricately determined by the balance between AM transport by turbulence and the magnetic field. Notably, our results, in conjunction with recent insights into turbulence properties at low Ro (e.g. Kapyla 2024), align closely with observed magnetic field saturation patterns reported by Reiners (2022). We are also going to discuss the methods to justify the assumed turbulent effects.

pptx
9.9 MB

6/24

Yoshihisa

Non-thermal velocities in Corona and Coronal Rain

The coronal heating problem of why the corona reaches a million K relative to 6000 K at the photosphere is one of the key open questions in the stellar physics. From an observational perspective, non-thermal line broadening are observed and considered to be the indicator of heating properties. However, previous numerical simulations have not explained this observation. This work attempt to reproduce observed non-thermal vel. by taking into account turbulent heating. We also investigate the non-thermal vel. in the coronal rain.

pptx
12.9 MB

7/1

Kida

Canceled

7/8

Natsume

Comparison of multiple chromospheric lines for post-flare loop

pdf
3.3 MB

7/8

Guest
Seminar
15:30-17:00

Prof. Petr Heinzel
(Astronomical Institute, Czech Academy of Sciences and University of Wroclaw, Center of Excellence 'Solar and Stellar Activity')

Radiative transfer in solar prominences: A historical overview and current trends

Similarly as in other branches of solar atmospheric spectroscopy, development of the non-LTE (i.e. departures from Local Thermodynamic Equilibrium) physics and related numerical tools in 60-ties and 70-ties of the last century largely influenced also the prominence research. First 1D prominence models have been constructed showing the critical importance of an external illumination in the relevant spectral lines and continua. Later on the effects of 2D geometry and partial redistribution have been investigated and the modeling turned to problems of heterogeneous media, multithread structures and finally studies of the energy balance. In parallel, new multi-wavelength spectral data became available at higher spatial and temporal resolution. We will review the progress from 70-ties till now and finally summarise the current modern trends in numerical non-LTE radiative-transfer modeling, focusing on both quiescent as well as eruptive prominences. Namely the coupling of up-to-date MHD simulations with optically-thick radiative transfer will be highlighted.

7/22

Suzuki

Observation of M dwarf's magnetic fields

Understanding details of the stellar winds of M-type stars is important for study of exoplanetary atmospheres. In order to simulate stellar winds, knowledge of magnetic fields of M dwarfs is required as a numerical setup. Here, I will summarize observational studies of magnetic fields of M dwarfs. They clarified magnetic field strength and geometries.

pdf
1.0 MB

Date

Name

Title

Abstract

File

10/7

Ueno

Compensation of the Instrumental Polarization of the Adaptive Optics (AO) on the Hida/DST and Improvement of the Accuracy of Spectro-polarimetry

In the instruments session of the ASJ 2024 fall meeting, I talked about compensation of the instrumental polarization of the permanently installed AO on the Hida/DST and improvement of the accuracy of spectro-polarimetry by AO. I think that many of members of the Solar Sminar didn't attend the instruments session. Therefore, I would like to explain the contents of that talk in this seminar again with adding some other information, such as instrumental polarization of the telescope itself, and future plans of the spectro-polarimetry with the DST.

pdf
6.6 MB

10/21

Ishii

Flares observed by SMART/SDDI in this year

Today, I would like to talk about flares observed by SMART/SDDI in this year. https://www.kwasan.kyoto-u.ac.jp/topics/kako.html
Iju-san will introduce the categories and examples of event report in 'observation log'. ex.) https://www.hida.kyoto-u.ac.jp/SMART/daily/24Oct/log/20241015_smart.log

pptx
4.3 MB

10/28

Special Seminar

11/11

Shirato

11/18

interim report

Otsu

11/25

Suzuki

12/2

Mishra

12/9

Guest Seminar

Annan

12/16

Dai

12/23

Shimada

1/6

Ichihara

1/20

Natsume

1/27

Yoshihisa