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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
6/16	13:30-15:00		Mishra	upload or download

Please upload your presentation file!!

Date	Section	Speaker	File
4/14		Asai	upload or download
4/21		Ueno	upload or download
4/28		Ishii	upload or download
5/12		Dai	upload or download
5/12		Shirato	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If you do not want to make public your unpublished results, please delete the relevant part before submission.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
4/14		Asai
4/21		Ueno	Multi-wavelength 2D Spectroscopy of the Solar Flare at δ-type Sunspot Region	At the ASJ Annual Meeting last month, I reported on results of the analysis of multi-wavelength spectroheliograph data (H-alpha, H-beta, H-gamma and CaII K) on the M-class flare that occurred on November 25, 2024 and a dark filament, plage around δ-type sunspot region (AR13906). However, since I couldn't make time for discussion at the ASJ meeting, I would like to introduce these analyses again in this Solar Seminar with adding some additional slides.
4/28		Ishii		Today, I would like to introduce following paper, Identifying Coronal Mass Ejection Active Region Sources: An Automated Approach Julio Hernandez Camero(1), Lucie M. Green(1), and Alex Pinel Neparidze(2) (1)Mullard Space Science Laboratory, University College London, UK (2)University College London, UK ApJ, 973, 63, 2025 https://ui.adsabs.harvard.edu/abs/2025ApJ...979...63H/abstract
5/12		Dai	End-view Observations of longitudinal oscillations of a quiescent prominence	Combining the Doppler velocities derived from the spectroscopic data provided by CHASE/HIS and SDO/AIA EUV data, we present the end-view Observations of longitudinal oscillations of a quiescent prominence, Based on the 3D velocity (values and directions) variations of the oscillation, we confirmed that the direction of the oscillations was longitudinal, and the geometry of the magnetic dip could be accurately described: the curvature radius of the magnetic dip was the smallest at its bottom and increased towards the sides, with a range of values of 87-258 Mm. Compared to the general pendulum model (Semicircular geometry), the calculations based on the variation of V3D are more realistic and accurate.
5/19		Shirato	Report on the re-analysis of full-disk oscillation data	In addressing the chromospheric and coronal heating problem, it is essential to clarify the relationship between wave propagation in the solar atmosphere and magnetic field structures in order to understand the mechanisms of energy transport to the upper layers from the perspective of wave dynamics. In particular, in quiet-Sun regions, a key focus is how low-frequency acoustic waves propagate into the upper atmosphere and dissipate their energy. It has been proposed that when relatively strong, inclined magnetic fields are present, the acoustic cutoff frequency is reduced, allowing low-frequency waves to leak into the chromosphere (De Pontieu et al. 2004). Indeed, observational studies have reported that magnetic elements and chromospheric mottles often exhibit oscillations with periods of 5–7 minutes, whereas 3-minute oscillations are more common within the internetwork regions (Jess et al. 2023). However, most of the observational studies conducted thus far have been limited to small areas near the disk center and short time spans of only 2–3 hours at most. In this study, we analyzed over 12 hours of full-disk spectroscopic imaging data in the Hα line obtained on May 4, 2022, with the SMART/SDDI instrument at Hida Observatory, Kyoto University. We investigated the spatial distribution of oscillation power in Doppler velocity and intensity through time-series analysis. As a result, in addition to the commonly observed 3- and 5-minute chromospheric oscillations, we found the presence of oscillations with a 20-minute period across the entire solar disk. Notably, the 20-minute oscillation power showed a remarkable spatial correlation with inclined magnetic fields in quiet regions, as well as with strong magnetic field regions such as enhanced network, plage, and active regions. We also observed that the oscillation power tended to be stronger closer to the limb. Due to the short duration of past observations, there have been very few reports of such 20-minute oscillations, and their nature remains unclear. Furthermore, we focused on quiet-Sun regions to examine the center-to-limb variation of oscillation power and phase difference, and explored the relationship with network structures. In this presentation, we report these findings and discuss their implications.
6/2		Otsu	Broadening of Hydrogen Balmer lines during flares ~Simple Model Using SPECTRA code~	Solar and stellar flares often exhibit line broadenings in Balmer lines such as Hα during their impulsive pahses. Such broadeningsare thought to come from chromospheric condensation, and they give infomation of elecron density of condensation region. In Suemoto&Hiei 1959, they observed a solar flare with Balmer lines from Hα (H2) to H14 and obtained Full Width at Half Maximum (FWHM). The relation between FWHM and quantum number of upper level showed 'dip' structure, which can be explained with self-absorption and Stark broadening. Moreover, this relation can be used to obtain electron density at condensation region. Recently, I have been working on reconstructing the results of Suemto&Hiei 1959 to deepen my understanding of line broadening related to self absorption and Stark effect. In today's talk, I will share some reconstructed results. I will also mention line strength ratios of Balmer lines. Suemoto&Hiei 1959: Balmer Series Lines of the Flare and its Structure - Astrophysics Data System
6/9	Guest Seminar	Yamasaki	Magnetic field diagnostic of solar filaments with spectropolarimetric observations in He I 10830 Å	Solar filaments are dense cool plasma in the solar corona. They are supported in a dip of coronal magnetic field. There are two classical models of magnetic field configuration of solar filaments; one is the normal polarity model proposed by Kippenhahn & Schlueter (1957), and the other is the reverse polarity model proposed by Kuperus & Raadu (1974). These two models are identified by the tilt direction between the magnetic field of the filament and polarity inversion line (PIL). To understand the mechanism that makes filaments unstable before their eruptions and/or solar flares, it is critical to confirm the magnetic field configuration of solar filaments. Previously, we have performed the He I 10830 Å spectropolarimetric observation targeting on quiet sun filaments with the Domeless Solar Telescope (DST) at Hida Observatory. We found that the magnetic field strength was 8-35 G and majority of the magnetic field configuration was reverse polarity (Yamasaki et al. 2023). In this study, we performed the same observation but targeting on an active region filament, which appeared in AR NOAA 13092 on September 5, 2022. The observation was carried out one hour after C class flare. As a result of our analysis of full Stokes profiles, we found the followings: deviation of the filament position from the PIL of about 10000 km, magnetic field strength of the filaments of 101±33 G, and counter-streaming flow along the filament axis with about 10 km/s. By comparing the direction of the magnetic field in filaments and the global distribution of the photospheric magnetic field, we suggested that the magnetic field configuration of the filament was intermediate of the two classical models, i.e., magnetic field of the filament was almost parallel to the PIL. In our presentation, we will also discuss the interpretation of strong Zeeman-like Stokes profiles found in linear polarization, and disambiguation method in our Stokes inversion. Furthermore, we will present the DST observation plan for this year.
6/16		Mishra
6/23		Shimada
6/30		Natsume
7/7		Yoshihisa
7/14		Ichihara

Date

Name

Title

Abstract

File

4/14

Asai

4/21

Ueno

Multi-wavelength 2D Spectroscopy of the Solar Flare at δ-type Sunspot Region

At the ASJ Annual Meeting last month, I reported on results of the analysis of multi-wavelength spectroheliograph data (H-alpha, H-beta, H-gamma and CaII K) on the M-class flare that occurred on November 25, 2024 and a dark filament, plage around δ-type sunspot region (AR13906). However, since I couldn't make time for discussion at the ASJ meeting, I would like to introduce these analyses again in this Solar Seminar with adding some additional slides.

4/28

Ishii

Today, I would like to introduce following paper,

Identifying Coronal Mass Ejection Active Region Sources: An Automated Approach
Julio Hernandez Camero(1), Lucie M. Green(1), and Alex Pinel Neparidze(2)
(1)Mullard Space Science Laboratory, University College London, UK
(2)University College London, UK
ApJ, 973, 63, 2025
https://ui.adsabs.harvard.edu/abs/2025ApJ...979...63H/abstract

5/12

Dai

End-view Observations of longitudinal oscillations of a quiescent prominence

Combining the Doppler velocities derived from the spectroscopic data provided by CHASE/HIS and SDO/AIA EUV data, we present the end-view Observations of longitudinal oscillations of a quiescent prominence, Based on the 3D velocity (values and directions) variations of the oscillation, we confirmed that the direction of the oscillations was longitudinal, and the geometry of the magnetic dip could be accurately described: the curvature radius of the magnetic dip was the smallest at its bottom and increased towards the sides, with a range of values of 87-258 Mm. Compared to the general pendulum model (Semicircular geometry), the calculations based on the variation of V3D are more realistic and accurate.

5/19

Shirato

Report on the re-analysis of full-disk oscillation data

In addressing the chromospheric and coronal heating problem, it is essential to clarify the relationship between wave propagation in the solar atmosphere and magnetic field structures in order to understand the mechanisms of energy transport to the upper layers from the perspective of wave dynamics. In particular, in quiet-Sun regions, a key focus is how low-frequency acoustic waves propagate into the upper atmosphere and dissipate their energy. It has been proposed that when relatively strong, inclined magnetic fields are present, the acoustic cutoff frequency is reduced, allowing low-frequency waves to leak into the chromosphere (De Pontieu et al. 2004). Indeed, observational studies have reported that magnetic elements and chromospheric mottles often exhibit oscillations with periods of 5–7 minutes, whereas 3-minute oscillations are more common within the internetwork regions (Jess et al. 2023). However, most of the observational studies conducted thus far have been limited to small areas near the disk center and short time spans of only 2–3 hours at most.
In this study, we analyzed over 12 hours of full-disk spectroscopic imaging data in the Hα line obtained on May 4, 2022, with the SMART/SDDI instrument at Hida Observatory, Kyoto University. We investigated the spatial distribution of oscillation power in Doppler velocity and intensity through time-series analysis. As a result, in addition to the commonly observed 3- and 5-minute chromospheric oscillations, we found the presence of oscillations with a 20-minute period across the entire solar disk. Notably, the 20-minute oscillation power showed a remarkable spatial correlation with inclined magnetic fields in quiet regions, as well as with strong magnetic field regions such as enhanced network, plage, and active regions. We also observed that the oscillation power tended to be stronger closer to the limb. Due to the short duration of past observations, there have been very few reports of such 20-minute oscillations, and their nature remains unclear. Furthermore, we focused on quiet-Sun regions to examine the center-to-limb variation of oscillation power and phase difference, and explored the relationship with network structures. In this presentation, we report these findings and discuss their implications.

6/2

Otsu

Broadening of Hydrogen Balmer lines during flares ~Simple Model Using SPECTRA code~

Solar and stellar flares often exhibit line broadenings in Balmer lines such as Hα during their impulsive pahses. Such broadeningsare thought to come from chromospheric condensation, and they give infomation of elecron density of condensation region. In Suemoto&Hiei 1959, they observed a solar flare with Balmer lines from Hα (H2) to H14 and obtained Full Width at Half Maximum (FWHM). The relation between FWHM and quantum number of upper level showed 'dip' structure, which can be explained with self-absorption and Stark broadening. Moreover, this relation can be used to obtain electron density at condensation region.
Recently, I have been working on reconstructing the results of Suemto&Hiei 1959 to deepen my understanding of line broadening related to self absorption and Stark effect. In today's talk, I will share some reconstructed results. I will also mention line strength ratios of Balmer lines.

Suemoto&Hiei 1959:
Balmer Series Lines of the Flare and its Structure - Astrophysics Data System

6/9

Guest Seminar

Yamasaki

Magnetic field diagnostic of solar filaments with spectropolarimetric observations in He I 10830 Å

Solar filaments are dense cool plasma in the solar corona. They are supported in a dip of coronal magnetic field. There are two classical models of magnetic field configuration of solar filaments; one is the normal polarity model proposed by Kippenhahn & Schlueter (1957), and the other is the reverse polarity model proposed by Kuperus & Raadu (1974). These two models are identified by the tilt direction between the magnetic field of the filament and polarity inversion line (PIL). To understand the mechanism that makes filaments unstable before their eruptions and/or solar flares, it is critical to confirm the magnetic field configuration of solar filaments. Previously, we have performed the He I 10830 Å spectropolarimetric observation targeting on quiet sun filaments with the Domeless Solar Telescope (DST) at Hida Observatory. We found that the magnetic field strength was 8-35 G and majority of the magnetic field configuration was reverse polarity (Yamasaki et al. 2023). In this study, we performed the same observation but targeting on an active region filament, which appeared in AR NOAA 13092 on September 5, 2022. The observation was carried out one hour after C class flare. As a result of our analysis of full Stokes profiles, we found the followings: deviation of the filament position from the PIL of about 10000 km, magnetic field strength of the filaments of 101±33 G, and counter-streaming flow along the filament axis with about 10 km/s. By comparing the direction of the magnetic field in filaments and the global distribution of the photospheric magnetic field, we suggested that the magnetic field configuration of the filament was intermediate of the two classical models, i.e., magnetic field of the filament was almost parallel to the PIL. In our presentation, we will also discuss the interpretation of strong Zeeman-like Stokes profiles found in linear polarization, and disambiguation method in our Stokes inversion. Furthermore, we will present the DST observation plan for this year.

6/16

Mishra

6/23

Shimada

6/30

Natsume

7/7

Yoshihisa

7/14

Ichihara

Date

Name

Title

Abstract

File

10/6

Nagata

10/20

10/27

11/10

11/17

12/1

12/8

12/15

12/22

1/5

1/19

1/26