Solar Seminar home page (FY2020)

Solar Seminar (13:30-15:00 Monday, Room 504 5th floor building 4) Access

Next presenters

Date	Time	Section	Speaker	File
2-1	13:30-14:15	M2 presentation	H. Tanaka	upload or download
2-1	14:15-15:00	M2 presentation	N. Kimura	upload or download
2-1	15:00-15:45	M2 presentation	Y. Tomino	upload or download

Please upload your presentation file!!

Date	Section	Speaker	File
4-20	long	K. Ichimoto	upload or download
4-27	long	A. Asai	upload or download
6-15	main	A.D. Kawamura	upload or download
7-6	short	N. Kimura	upload or download
10-26	short	S. Nagata	upload or download
11-30	short	A. D. Kawamura	upload or download
1-12	D3 presentation	T. Sakaue	upload or download
1-12	D3 presentation	K. Namekata	upload or download

For Speakers

Presentation time for speaker is: main : 40 minutes as a guide, and 20 minutes discussion.
short : 20 minutes as a guide, and 10 minutes discussion.
Contents of talk are: main : about your study
short : 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 is very big, please zip the file before uploading.
If you do not want to make public your unpublished results, please delete the relevant part and submit it.

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
10-05	short	H. Tanaka		I want to introduce the paper, ‘MAGNETIC AND RADIATIVE VARIABILITY OF SOLAR SURFACE STRUCTURES. I. IMAGE DECOMPOSITION AND MAGNETIC-INTENSITY MAPPING’. In this paper, they isolated active regions, decaying active regions, the enhanced network, the network and quiet atmosphere. Then, they search relation between magnetic flux and Ca II K intensity (\|B\| vs δK). In the range 30-400 Mx cm^-2, the Ca II K residual intensity is proportional to the half-power of the magnetic flux density.	pptx
	main	K. Namekata	Stellar superflares on late-type stars - recent progress by space/ground-based survey -	Solar flares are explosive phenomena on the solar surface. They often produce high XUV radiations and mass ejections which have potential risks to damage human technologies. On other stars, such as M dwarfs and young stars, larger ‘superflares’ (more than ten times larger than the most energetic solar flares) are known to frequently occur, severely affecting the exoplanet. Recently, there is an increasing interest in stellar superflares in terms of the exoplanet habitability and possible superflares on the current Sun. The Kepler space telescope revealed that superflares actually occur on slowly rotating Sun-like stars, which supports a possibility of superflares on the current Sun (Maehara et al. 2012, Nature). We have investigated the photometric properties of the stellar superflares and large starspots with the Kepler data and found that its basic mechanism is common with solar phenomena (i.e. the release of magnetic energy). More recently, we have conducted optical spectroscopic observations of stellar superflares on G-/M-dwarfs with the 3.8-m Seimei Telescope and other space-/ground-based telescope. We found the first, conclusive evidence of stellar mass ejection, and also found the basic properties can be understood by solar physics (Namekata et al. submitted). These findings indicate the universal mechanism of solar and stellar flares and have enabled us to estimate its impacts on exoplanets. In this seminar, I will review the statistical properties of stellar superflares revealed by Kepler and also talk about my recent progress by Seimei Telescope.	pdf
10-12	short	Y. Tomino		In my short talk, I will introduce the following paper. "Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere" B. Snow and A. Hillier A&A 637, A97 (2020)	pptx MB
	main	K. Kihara	"Statistical Analysis of the Relation between Coronal Mass Ejections and Solar Energetic Particles" Kihara et al., 2020, ApJ, 900, 75	To improve the forecasting capability of impactful solar energetic particle (SEP) events, the relation between coronal mass ejections (CMEs) and SEP events needs to be better understood. Here we present a statistical study of SEP occurrences and timescales with respect to the CME source locations and speeds, considering all 257 fast (v_CME ≥ 900 km/s) and wide (angular width ≥60°) CMEs that occurred between 2006 December and 2017 October. We associate them with SEP events at energies above 10 MeV. Examination of the source region of each CME reveals that CMEs more often accompany a SEP event if they originate from the longitude of E20-W100 relative to the observer. However, an SEP event could still be absent if the CME is <2000 km/s. For the associated CME-SEP pairs, we compute three timescales for each of the SEP events, namely the timescale of the onset (TO), the rise time (TR), and the duration (TD). They are correlated with the longitude of the CME source region relative to the footpoint of the Parker spiral (∆Φ) and v_CME. The TO tends to be short for \|ΔΦ\| < 60°. This trend is weaker for TR and TD. The SEP timescales are only weakly correlated with v_CME. Positive correlations of both TR and TD with v_CME are seen in poorly connected (large \|ΔΦ\|) events. Additionally, TO appears to be negatively correlated with v_CME for events with small \|ΔΦ\|.	pdf MB
10-19	short	S. Ueno		I am planning to introduce the following paper about the relationship between recent prominence (filament) eruptions and CMEs, as my short talk of tomorrow. "Analysis of Large Deflections of Prominence-CME Events during the Rising Phase of Solar Cycle 24” by M. Valeria Sieyra, et al. Solar Physics, vol. 295, Article number: 126 (2020)	pdf
	main	Y. Kotani	Spectral analysis of rapid shift events observed by SMART/SDDI	Hida Observatory SMART/SDDI has found many blue (or red) shifts around Ha ± 1.5 Å for tens of seconds to a few minutes (rapid shift events). These blue (or red) shifts are thought to reflect some kind of sudden phenomena in the solar chromosphere, but it is not clear what they are. In this study, we attempted to clarify the nature of the rapid shift events by analyzing their spectra on days with good observation conditions. Spectral analysis and fitting with a cloud model confirmed that the rapid shift events are supersonic eruptions in the solar chromosphere. In this talk, I will present the results of the analysis to date and a possible theoretical model based on the results.	pptx
10-26	short	S. Nagata
	main	D. Yamasaki	Evolution of the non-potential magnetic field in the solar active region 12673 based on a nonlinear force-free modeling	Active region (AR) 12673 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 hours from September 4th 00:00 UT to 6th 00:00 UT. Our analysis found that three magnetic flux ropes (MFRs) are formed by September 4th, one of which produced the X9.3 flare on September 6th. One MFR has positive magnetic twist which is a different sign from 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 4th to 6th, 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 the AIA 1600 A 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 drived the M5.5 flare.	pdf
11-02	short	H. Isobe		I will introduce a paper on historical sunspot observation just before the Maunder minimum. "Sunspot Characteristics at the Onset of the Maunder Minimum Based on the Observations of Hevelius” Carrasco et al., ApJ, 866:18 (2019)	pptx
	main	N. Kimura	Determination of 3D velocity fields of the erupting solar filament on 2016 August 9 using SMART/SDDI at Hida Observatory	Space weather means the environmental changes around the earth due to solar activity. When a flare, explosion on the surface of the sun, occurs, the earth is affected by magnetic storms and increasing radiation and infrastructures are damaged by high energy particles, therefore it is needed to forecast a space weather. In particular, filament eruption and disappearance, the event that cooler plasma floating on the atmosphere of the sun erupt into the interplanetary space, highly related to the coronal mass ejection which is the emission of large amounts of solar plasma into the interplanetary space. It is thought to be one of the reason of magnetic storms, however, the relationship between filament eruption and disappearance, coronal mass ejection, magnetic storms has not yet been clarified. This is because it is necessary to accurately measure the velocity field of the plasma of the filament in order to determine whether the plasma is actually ejected into the interplanetary space. It is impossible to obtain field of the filament plasma only by H-alpha line(6562.808 Angstrom), so we use the SDDI (Solar Dynamics Doppler Imager) installed in SMART (Solar Magnetic Activity Research Telescope) in Hida observatory that can take the solar chromospheric full-disk dataset with 0.25 Angstrom step between -9 to +9 Angstrom centered at H-alpha line. In this study, Becker’s “cloud model” is applied to the filament observation at 73 wavelengths and we can get the line of sight velocity. We calculated the line of sight velocities of the filament observed on 2016 August 9th to 10th. This event is occurred at the coordinates (x, y) = (-825,319) around the east limb of the sun and CME was occurred immediately after that. It was possible to track the three dimensional shape change of the filament structure entirely from the pre-ejection stage to the ejection finish by combining the gaze direction velocity field and the visual motion on the AIA images. This filament erupted to 150km/s, the maximum speed from the surface of the sun, and the large CME had occurred to 370km/s in Aug 10th 4:00UT, after the eruption. We compared those two velocities and try to find the transient from of them. We also traced the time variations of the directions of the filament movement by observing the plasma blobs in the filament in detail. In my talk, I will report about the time variation of fine structure of the filament.	pdf MB
11-09	short	T. T. Ishii		Today, I would like to talk about 'White light flare and red asymmetry observed with SMART (Solar Magnetic Activity Research Telescope) / SDDI (Solar Dynamics Doppler Imager) and FISCH (Flare Imaging System in Continuum and H-alpha) on 2017-Sep-05'.	pptx
	main	H. Tanaka			pptx MB
11-16	short	K. Nishida		In today's solar seminar, I will talk about "3-dimensional MHD simulations of Solar jets". This is part of the following paper in preparation: K.A.P. Singh, Keisuke Nishida & Kazunari Shibata, Launching of small-scale successive jets from calcium bright knots and formation of chromospheric anemone jets .	pdf
	main	Y. Tomino	Magnetic reconnection in partially ionized plasma	Magnetic reconnection is the important process of energy release of solar flares and flare-like phenom- ena and the physical process occurs ubiquitously in the solar atmosphere, even in the chromosphere. The chromosphere consists of partially ionized plasma (ions, electrons and neutrals), and hence we should understand the magnetic reconnection in a partially ionized plasma. There are two methods to investigate the physical process in partially ionized plasma. One is to perform numerical simulations with single fluid equation including ambipolar diffusivity. On the other hand, the other is to run calculations with two-fluid equations, assuming that partially ionized plasma consists of plasma and neutral fluid. We investigate Petschek-type reconnection of partially ionized plasma by running 2D numerical simulation and compare simulation results of single fluid with those of two-fluid. We reveal that the single fluid simulation results and two-fluid simulation results are different in the case of large ambipolar diffusivity, and that there is no sharp discontinuity of gas pressure in single fluid simulations but a shock wave structure which reflects slow shock of plasma exists in two-fluid simulations. Also, the velocity difference between two species is about three times smaller than expected in single fluid approximation. In addition, we calculate reconnection rate in each case. There is about 10% difference between single fluid results and two-fluid results.	pptx MB
11-30	short	A. D. Kawamura		As for the tomorrow's short talk, I will briefly introduce the following proceeding paper. N. Gopalswamy+ (2020) Effect of the Weakened Heliosphere in Solar Cycle 24 on the Properties of Coronal Mass Ejections https://iopscience.iop.org/article/10.1088/1742-6596/1620/1/012005/meta	MB
	main	D. Inoue		太陽大気中では、約10eV以下の第一電離ポテンシャル(First Ionization Potential, FIP)をもつ元素の割合がコロナ中で光球中と比べ大きくなる、という現象(FIP効果)が知られている。 FIP効果は彩層プラズマの部分電離性によって引き起こされると考えられている。 FIP効果の現れ方は、活動領域からのアウトフローや太陽風など、比較的定常的な現象については様々な研究がなされている(Brooks and Warren 2011など)。太陽大気での太陽フレアやジェットといった突発的に起こる現象についてはFIP効果の強さが定常現象のものと異なる振る舞いをしていることはわかっているものの（Dennis et al. 2015など)、典型的な強さや統一的な見解は得られていない。とくにFIP効果の時間的・空間的変動について研究したものはほとんどなく、彩層プラズマのダイナミクスやジェットの起源の解明を考える上で、より詳細な研究が必要とされている。本研究では「ひので」衛星の極端紫外線撮像分光装置の分光観測により得られた2017年4月2日に起きたジェット現象についてFIP効果の時間的・空間的変動を調べた。Ca XIVとNi XVIの輝線強度をFIPが低い元素の寄与、 Ar XIVの輝線強度をFIPが高い元素の寄与として採用し、ジェット現象とその周辺で強度比がどのように分布しているのかを確かめた。その結果、ジェットが見られる時間帯にジェット領域でFIP効果の表れがあることが分かった。	pptx MB
12-07	short	C. Denis		I will briefly introduce the following paper entitled: Spectral diagnostics of cool flare loops observed by SST: I. Inversion of the Ca II 8542A and H-beta lines. J. Koza et. al 2019. ApJ 885, 154. https://ui.adsabs.harvard.edu/abs/2019ApJ...885..154K/abstract	pdf MB
	main	H. Shirato		太陽コロナの温度は光球よりも数百万Kも高い。エネルギー源が太陽内部にあるにも関わらず、彩層から遷移領域を経てコロナに至る僅かな高度差の間になぜこんなに温度が上がるのかという疑問はコロナ加熱問題と呼ばれる。未だ統一的な理解はされておらず、太陽物理学における大きな謎のひとつである。これまでいくつかの理論が提唱されているが、中でも「波動説」に注目する。波動説とは、光球で励起された波が上方に伝播し減衰することでエネルギーを上層に注入するというものである。周期の長い波は重力の影響でエバネッセントになると一般的に考えられているが、強磁場が存在する領域では長周期の波も彩層に漏れ出て行く可能性があることが指摘されている（Michalitsanos 1973; Bel & Leroy 1977; Suematsu1990）。また、磁場の強さだけでなく、波の磁力線への入射角によっても透過および反射の割合が異なるという議論も行われている（Kontogiannis et al. 2010a, b, 2014）。本研究では、飛騨天文台のSMART/SDDIで観測したＨαコアのデータから、disc centerでの、速度場や光度などのパワースペクトルや位相変化、ネットワーク領域との空間的な位置関係を調べ、長周期波と磁場との関係を探った。今回の発表ではその研究報告を行う。	pptx MB
01-12	D3 presentation	T. Sakaue
01-12	D3 presentation	K. Namekata
01-26	D3 presentation	D. Seki			pdf
02-01	M2 presentation	H. Tanaka
	M2 presentation	N. Kimura
	M2 presentation	Y. Tomino

Date

Name

Title

Abstract

File

10-05

short

H. Tanaka

I want to introduce the paper, ‘MAGNETIC AND RADIATIVE VARIABILITY OF SOLAR SURFACE STRUCTURES. I. IMAGE DECOMPOSITION AND MAGNETIC-INTENSITY MAPPING’. In this paper, they isolated active regions, decaying active regions, the enhanced network, the network and quiet atmosphere. Then, they search relation between magnetic flux and Ca II K intensity (|B| vs δK). In the range 30-400 Mx cm^-2, the Ca II K residual intensity is proportional to the half-power of the magnetic flux density.

pptx

main

K. Namekata

Stellar superflares on late-type stars - recent progress by space/ground-based survey -

Solar flares are explosive phenomena on the solar surface. They often produce high XUV radiations and mass ejections which have potential risks to damage human technologies. On other stars, such as M dwarfs and young stars, larger ‘superflares’ (more than ten times larger than the most energetic solar flares) are known to frequently occur, severely affecting the exoplanet. Recently, there is an increasing interest in stellar superflares in terms of the exoplanet habitability and possible superflares on the current Sun. The Kepler space telescope revealed that superflares actually occur on slowly rotating Sun-like stars, which supports a possibility of superflares on the current Sun (Maehara et al. 2012, Nature). We have investigated the photometric properties of the stellar superflares and large starspots with the Kepler data and found that its basic mechanism is common with solar phenomena (i.e. the release of magnetic energy). More recently, we have conducted optical spectroscopic observations of stellar superflares on G-/M-dwarfs with the 3.8-m Seimei Telescope and other space-/ground-based telescope. We found the first, conclusive evidence of stellar mass ejection, and also found the basic properties can be understood by solar physics (Namekata et al. submitted). These findings indicate the universal mechanism of solar and stellar flares and have enabled us to estimate its impacts on exoplanets. In this seminar, I will review the statistical properties of stellar superflares revealed by Kepler and also talk about my recent progress by Seimei Telescope.

pdf

10-12

short

Y. Tomino

In my short talk, I will introduce the following paper.

"Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere" B. Snow and A. Hillier A&A 637, A97 (2020)

pptx
MB

main

K. Kihara

"Statistical Analysis of the Relation between Coronal Mass Ejections and Solar Energetic Particles"

Kihara et al., 2020, ApJ, 900, 75

To improve the forecasting capability of impactful solar energetic particle (SEP) events, the relation between coronal mass ejections (CMEs) and SEP events needs to be better understood. Here we present a statistical study of SEP occurrences and timescales with respect to the CME source locations and speeds, considering all 257 fast (v_CME ≥ 900 km/s) and wide (angular width ≥60°) CMEs that occurred between 2006 December and 2017 October. We associate them with SEP events at energies above 10 MeV. Examination of the source region of each CME reveals that CMEs more often accompany a SEP event if they originate from the longitude of E20-W100 relative to the observer. However, an SEP event could still be absent if the CME is <2000 km/s. For the associated CME-SEP pairs, we compute three timescales for each of the SEP events, namely the timescale of the onset (TO), the rise time (TR), and the duration (TD). They are correlated with the longitude of the CME source region relative to the footpoint of the Parker spiral (∆Φ) and v_CME. The TO tends to be short for |ΔΦ| < 60°. This trend is weaker for TR and TD. The SEP timescales are only weakly correlated with v_CME. Positive correlations of both TR and TD with v_CME are seen in poorly connected (large |ΔΦ|) events. Additionally, TO appears to be negatively correlated with v_CME for events with small |ΔΦ|.

pdf
MB

10-19

short

S. Ueno

I am planning to introduce the following paper about the relationship between recent prominence (filament) eruptions and CMEs, as my short talk of tomorrow.

"Analysis of Large Deflections of Prominence-CME Events during the Rising Phase of Solar Cycle 24” by M. Valeria Sieyra, et al. Solar Physics, vol. 295, Article number: 126 (2020)

pdf

main

Y. Kotani

Spectral analysis of rapid shift events observed by SMART/SDDI

Hida Observatory SMART/SDDI has found many blue (or red) shifts around Ha ± 1.5 Å for tens of seconds to a few minutes (rapid shift events). These blue (or red) shifts are thought to reflect some kind of sudden phenomena in the solar chromosphere, but it is not clear what they are. In this study, we attempted to clarify the nature of the rapid shift events by analyzing their spectra on days with good observation conditions. Spectral analysis and fitting with a cloud model confirmed that the rapid shift events are supersonic eruptions in the solar chromosphere. In this talk, I will present the results of the analysis to date and a possible theoretical model based on the results.

pptx

10-26

short

S. Nagata

main

D. Yamasaki

Evolution of the non-potential magnetic field in the solar active region 12673 based on a nonlinear force-free modeling

Active region (AR) 12673 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 hours from September 4th 00:00 UT to 6th 00:00 UT. Our analysis found that three magnetic flux ropes (MFRs) are formed by September 4th, one of which produced the X9.3 flare on September 6th. One MFR has positive magnetic twist which is a different sign from 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 4th to 6th, 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 the AIA 1600 A 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 drived the M5.5 flare.

pdf

11-02

short

H. Isobe

I will introduce a paper on historical sunspot observation just before the Maunder minimum.

"Sunspot Characteristics at the Onset of the Maunder Minimum Based on the Observations of Hevelius” Carrasco et al., ApJ, 866:18 (2019)

pptx

main

N. Kimura

Determination of 3D velocity fields of the erupting solar filament on 2016 August 9 using SMART/SDDI at Hida Observatory

Space weather means the environmental changes around the earth due to solar activity. When a flare, explosion on the surface of the sun, occurs, the earth is affected by magnetic storms and increasing radiation and infrastructures are damaged by high energy particles, therefore it is needed to forecast a space weather. In particular, filament eruption and disappearance, the event that cooler plasma floating on the atmosphere of the sun erupt into the interplanetary space, highly related to the coronal mass ejection which is the emission of large amounts of solar plasma into the interplanetary space. It is thought to be one of the reason of magnetic storms, however, the relationship between filament eruption and disappearance, coronal mass ejection, magnetic storms has not yet been clarified. This is because it is necessary to accurately measure the velocity field of the plasma of the filament in order to determine whether the plasma is actually ejected into the interplanetary space. It is impossible to obtain field of the filament plasma only by H-alpha line(6562.808 Angstrom), so we use the SDDI (Solar Dynamics Doppler Imager) installed in SMART (Solar Magnetic Activity Research Telescope) in Hida observatory that can take the solar chromospheric full-disk dataset with 0.25 Angstrom step between -9 to +9 Angstrom centered at H-alpha line. In this study, Becker’s “cloud model” is applied to the filament observation at 73 wavelengths and we can get the line of sight velocity. We calculated the line of sight velocities of the filament observed on 2016 August 9th to 10th. This event is occurred at the coordinates (x, y) = (-825,319) around the east limb of the sun and CME was occurred immediately after that. It was possible to track the three dimensional shape change of the filament structure entirely from the pre-ejection stage to the ejection finish by combining the gaze direction velocity field and the visual motion on the AIA images. This filament erupted to 150km/s, the maximum speed from the surface of the sun, and the large CME had occurred to 370km/s in Aug 10th 4:00UT, after the eruption. We compared those two velocities and try to find the transient from of them. We also traced the time variations of the directions of the filament movement by observing the plasma blobs in the filament in detail. In my talk, I will report about the time variation of fine structure of the filament.

pdf
MB

11-09

short

T. T. Ishii

Today, I would like to talk about 'White light flare and red asymmetry observed with SMART (Solar Magnetic Activity Research Telescope) / SDDI (Solar Dynamics Doppler Imager) and FISCH (Flare Imaging System in Continuum and H-alpha) on 2017-Sep-05'.

pptx

main

H. Tanaka

pptx
MB

11-16

short

K. Nishida

In today's solar seminar, I will talk about "3-dimensional MHD simulations of Solar jets". This is part of the following paper in preparation: K.A.P. Singh, Keisuke Nishida & Kazunari Shibata, Launching of small-scale successive jets from calcium bright knots and formation of chromospheric anemone jets .

pdf

main

Y. Tomino

Magnetic reconnection in partially ionized plasma

Magnetic reconnection is the important process of energy release of solar flares and flare-like phenom- ena and the physical process occurs ubiquitously in the solar atmosphere, even in the chromosphere. The chromosphere consists of partially ionized plasma (ions, electrons and neutrals), and hence we should understand the magnetic reconnection in a partially ionized plasma. There are two methods to investigate the physical process in partially ionized plasma. One is to perform numerical simulations with single fluid equation including ambipolar diffusivity. On the other hand, the other is to run calculations with two-fluid equations, assuming that partially ionized plasma consists of plasma and neutral fluid. We investigate Petschek-type reconnection of partially ionized plasma by running 2D numerical simulation and compare simulation results of single fluid with those of two-fluid. We reveal that the single fluid simulation results and two-fluid simulation results are different in the case of large ambipolar diffusivity, and that there is no sharp discontinuity of gas pressure in single fluid simulations but a shock wave structure which reflects slow shock of plasma exists in two-fluid simulations. Also, the velocity difference between two species is about three times smaller than expected in single fluid approximation. In addition, we calculate reconnection rate in each case. There is about 10% difference between single fluid results and two-fluid results.

pptx
MB

11-30

short

A. D. Kawamura

As for the tomorrow's short talk, I will briefly introduce the following proceeding paper.

N. Gopalswamy+ (2020) Effect of the Weakened Heliosphere in Solar Cycle 24 on the Properties of Coronal Mass Ejections https://iopscience.iop.org/article/10.1088/1742-6596/1620/1/012005/meta

main

D. Inoue

太陽大気中では、約10eV以下の第一電離ポテンシャル(First Ionization Potential, FIP)をもつ元素の割合がコロナ中で光球中と比べ大きくなる、という現象(FIP効果)が知られている。 FIP効果は彩層プラズマの部分電離性によって引き起こされると考えられている。 FIP効果の現れ方は、活動領域からのアウトフローや太陽風など、比較的定常的な現象については様々な研究がなされている(Brooks and Warren 2011など)。太陽大気での太陽フレアやジェットといった突発的に起こる現象についてはFIP効果の強さが定常現象のものと異なる振る舞いをしていることはわかっているものの（Dennis et al. 2015など)、典型的な強さや統一的な見解は得られていない。とくにFIP効果の時間的・空間的変動について研究したものはほとんどなく、彩層プラズマのダイナミクスやジェットの起源の解明を考える上で、より詳細な研究が必要とされている。本研究では「ひので」衛星の極端紫外線撮像分光装置の分光観測により得られた2017年4月2日に起きたジェット現象についてFIP効果の時間的・空間的変動を調べた。Ca XIVとNi XVIの輝線強度をFIPが低い元素の寄与、 Ar XIVの輝線強度をFIPが高い元素の寄与として採用し、ジェット現象とその周辺で強度比がどのように分布しているのかを確かめた。その結果、ジェットが見られる時間帯にジェット領域でFIP効果の表れがあることが分かった。

pptx
MB

12-07

short

C. Denis

I will briefly introduce the following paper entitled:

Spectral diagnostics of cool flare loops observed by SST: I. Inversion of the Ca II 8542A and H-beta lines. J. Koza et. al 2019. ApJ 885, 154.

https://ui.adsabs.harvard.edu/abs/2019ApJ...885..154K/abstract

pdf
MB

main

H. Shirato

太陽コロナの温度は光球よりも数百万Kも高い。エネルギー源が太陽内部にあるにも関わらず、彩層から遷移領域を経てコロナに至る僅かな高度差の間になぜこんなに温度が上がるのかという疑問はコロナ加熱問題と呼ばれる。未だ統一的な理解はされておらず、太陽物理学における大きな謎のひとつである。これまでいくつかの理論が提唱されているが、中でも「波動説」に注目する。波動説とは、光球で励起された波が上方に伝播し減衰することでエネルギーを上層に注入するというものである。周期の長い波は重力の影響でエバネッセントになると一般的に考えられているが、強磁場が存在する領域では長周期の波も彩層に漏れ出て行く可能性があることが指摘されている（Michalitsanos 1973; Bel & Leroy 1977; Suematsu1990）。また、磁場の強さだけでなく、波の磁力線への入射角によっても透過および反射の割合が異なるという議論も行われている（Kontogiannis et al. 2010a, b, 2014）。本研究では、飛騨天文台のSMART/SDDIで観測したＨαコアのデータから、disc centerでの、速度場や光度などのパワースペクトルや位相変化、ネットワーク領域との空間的な位置関係を調べ、長周期波と磁場との関係を探った。今回の発表ではその研究報告を行う。

pptx
MB

01-12

D3 presentation

T. Sakaue

01-12

D3 presentation

K. Namekata

01-26

D3 presentation

D. Seki

pdf

02-01

M2 presentation

H. Tanaka

M2 presentation

N. Kimura

M2 presentation

Y. Tomino

Date		Name	Title	Abstract	File
04-20	Long	K. Ichimoto			MB
04-27	Long	A. Asai			MB
05-11	short	Y.W. Huang		In this short presentation, I will introduce the following paper. Title : Spectro-polarimetric observations at the NVST: I. instrumental polarization calibration and primary measurements Authors : Jun-Feng Hou, Zhi Xu, Shu Yuan, Yu-Chao Chen, Jian-Guo Peng, Dong-Guang Wang, Jun Xu, Yuan-Yong Deng, Zhen-Yu Jin, Kai-Fan Ji and Zhong Liu DOI : https://doi.org/10.1088/1674-4527/20/4/45	pdf MB
	main	S. Ueno	Observational activities and a result of our researches in FY2019	This time, I would like to report observational activities and a result of our researches in FY2019, by using presentation slides for the joint meeting planned to be held on Apr-17 and the 4th PSTEP international symposium on Jan-30. Specifically, I introduce use-situation of the Domeless Solar Telescope for this one year, the recent condition of the CHAIN project, and the result of solar UV reproduction using long-term chromospheric (CaII K) full-disk data.	pdf MB
05-18	short	D. Seki	“SMART/SDDI Filament Disappearance Catalogue”	This paper describes a new “SMART/SDDI Filament Disappearance Catalogue,” in which we listed almost all the filament disappearance events that the Solar Dynamics Doppler Imager (SDDI) has observed since its installation on the Solar Magnetic Activity Research Telescope (SMART) in May 2016. Our aim is to build a database that can help predict the occurrence and severity of coronal mass ejections (CMEs). The catalogue contains miscellaneous information associated with filament disappearance such as flare, CME, active region, three-dimensional trajectory of erupting filaments, detection in Interplanetary Scintillation (IPS), occurrence of interplanetary CME (ICME) and Dst index. We also provide statistical information on the catalogue data. URL: https://www.kwasan.kyoto-u.ac.jp/observation/event/sddi-catalogue/ (or you can google “sddi catalogue”)	pdf MB
	main	S. Nagata			pptx MB
05-25	main	H. Isobe		Today I will talk about FIP and i-FIP effects based on following two papers: "Inverse First Ionization Potential Effects in Giant Solar Flares Found from Earth X-Ray Albedo with Suzaku/XIS” Katsuda, S. et al. (2020) The Astrophysical Journal, Volume 891, Issue 2, id.126 and "The FIP and Inverse FIP Effects in Solar and Stellar Coronae” Laming J. M. (2015), Living Reviews in Solar Physics, Volume 12, Issue 1, article id. 2	pptx MB
06-01	main	T.T. Ishii		Today, I would like to introduce SMART/SDDI event report. https://www.hida.kyoto-u.ac.jp/SMART/SDDI/event_report/	pptx
06-08	short	K. Namekata		In the short talk, I will talk about "Summary of stellar flare observations in 2019 by Seimei Telescope/OISTER".	pdf
	main	K. Nishida		In today's solar seminar, I will introduce the following paper: Tingyu Gou, Rui Liu, Bernhard Kliem, Yuming Wang, and Astrid M. Veronig The birth of a coronal mass ejection Science Advances 06 Mar 2019: Vol. 5, no. 3, eaau7004 https://advances.sciencemag.org/content/5/3/eaau7004	pptx
06-15	short	Y. Kotani		In tomorrow's solar seminar, I will introduce the following paper: Drews, Ainar & Rouppe van der Voort, Luc (2020) “A multi-diagnostic spectral analysis of penumbral microjets" https://ui.adsabs.harvard.edu/abs/2020arXiv200502608D/abstract	pptx
	main	A. D. Kawamura	"Updates on our CME statistics study: 150-year proxy of geo-effective flares & solar flare frequency”		MB
06-22	short	K. Kihara		I will introduce following paper. “Inferring Vector Magnetic Fields from Stokes profiles of GST/NIRIS Using a Convolutional Neural Network” https://ui.adsabs.harvard.edu/abs/2020ApJ...894...70L/abstract	pdf
	main	C. Denis	"A fast-filament eruption observed in the H-alpha line by SMART/SDDI: Imaging and spectroscopy diagnostic"	I will report on a filament eruption detected by SMART/SDDI on 2017 April 23. The eruption was observed in a wide spectral window around the H-alpha center. We investigated the dynamics of the filament eruption by applying the Cloud model and also the spectral analysis. The spectral analysis reveals strongly blue-shifted plasma up to -8.0Å from the line center, meaning that erupting material was ejected in direction to the Earth with a velocity of about 365 km/s. On the other hand, the estimated apparent velocity and acceleration at the filament apex, is about 800 km/s and 3.5 km/s2, respectively, which exhibit an exponential-like evolution. In my presentation I will give details of my analysis and also I will show some updates of my calculations.	pdf
06-29	M2 interim report	H. Tanaka	太陽のCaK線撮像分光観測による紫外線放射の推定	太陽活動は、 11 年で極大期と極小期をむかえる周期変動をしており、太陽活動が地球の気候に与える影響について研究されている (宇宙気候学)。太陽紫外線放射は、太陽活動と同期して、可視光 (太陽総放射量) に比べて大きく変動しており、特に地球の電離層に影響を与えている。しかし、紫外線は地上に届かず、人工衛星による観測が必須なので、継続的な観測は 1990 年代以降に限られる。そのため、長期の紫外線放射の変動は明らかにされていない。そこで、紫外線と CaK 線は、どちらも太陽の彩層が起原であり、相関が強いと考えられていることを利用する。 CaK 線は、地上からの過去の観測結果が残されている。 [観測波長幅と観測開始年が、それぞれ京都大学(0.74 Å、 1928 年)、国立天文台 (0.5 Å、 1917 年)、 Kodaikanal(0.5 Å、 1907 年)、 Mt.Wilson(0.2 Å、 1915年)] 本研究では、飛騨天文台ドームレス太陽望遠鏡 (DST) の水平分光器による 2010 年 8 月 22 日、 2012 年 8 月1 日、 2018 年 5 月 5 日の CaK 線の画像データと、人工衛星 SDO の紫外線観測装置 AIA による同日の紫外線 304 Å、 1600 Å、 1700 Åの画像データを用いた。 DST の波長分解能を生かし、 CaK 線の積分する波長幅を変え、どの波長幅が紫外線放射強度と相関がいいのかを調べた。その結果、紫外線の波長が長くなると、相関のいい波長幅は広くなることが分かった。また、波長幅が広いとき、明るい領域では、 CaK 強度の増加に比べて、紫外線強度の増加が大きいことが分かった。輝線や短い波長の紫外線を再現するには、 Mt.Wilson などの波長幅が狭いデータ、長い波長の紫外線を再現するには、Kyoto などの波長幅が広いデータを使う必要があると考えられる。修士論文に向けて、静穏領域と活動領域での違いを調べる、scatter plotの振る舞いの差から分かることを導き出すなどを行いたい	pptx MB
	M2 interim report	Y. Tomino	部分電離プラズマ中で起きる磁気リコネクションの数値的研究	約一万度の太陽彩層には部分電離プラズマが存在し、ジェット現象などの突発的なエネルギー解放現象が頻繁に起こっている。これらの現象のエネルギー解放過程では磁力線のつなぎ替え(磁気リコネクション)が重要な役割を果たし、それに伴って生じる衝撃波がプラズマの運動に大きく影響していると考えられている。そのため、磁気リコネクションで生じる衝撃波や磁場の構造を理解するための数値的研究(例 Yokoyama & Shibata 1998)は以前から行われてきた。また、部分電離プラズマの存在する彩層でのジェット現象に関しても同様に数値計算(例 Martínez-Sykora et al. 2017)によって盛んに研究されてきた。それらの研究では電離成分(イオンと電子)と中性成分(中性粒子)の混在する彩層を簡単のため一流体の電磁流体と近似している。しかし、電離成分と中性成分が混在している彩層を一流体として扱うことの妥当性は十分に検証されていない。実際に部分電離プラズマ中での衝撃波の発展に関して、一流体として計算した場合と二流体(電離成分と中性成分)で計算した場合に磁場の構造や圧力の分布が異なる結果になることが一次元の数値計算では示されている(Snow & Hillier 2019)。本研究では部分電離プラズマ中で磁気リコネクションが起きた際に、一流体で計算した場合と二流体方程式で計算した場合の結果の違いを二次元の数値シミュレーションを用いて調べた。計算の設定はZenitani & Miyoshi (2011)を参考にし、ペチェック型のリコネクションが起きるようにした。結果として電離成分の圧力にのみ衝撃波構造が生じることで、一流体での計算と二流体計算の結果に違いが生まれることが確認された。本発表ではこれまでの結果と今後の修士課程における研究の展望を報告する。	pptx
07-06	short	N. Kimura	Determination of 3D velocity fields of the erupting solar filament on 2016 August 9 using SMART/SDDI at Hida Observatory	Space weather means the environmental changes around the earth due to solar activity. When a flare, explosion on the surface of the sun, occurs, the earth is affected by magnetic storms and increasing radiation and infrastructures are damaged by high energy particles, therefore it is needed to forecast a space weather. In particular, filament eruption and disappearance, the event that cooler plasma floating on the atmosphere of the sun erupt into the interplanetary space, highly related to the coronal mass ejection which is the emission of large amounts of solar plasma into the interplanetary space. It is thought to be one of the reason of magnetic storms, however, the relationship between filament eruption and disappearance, coronal mass ejection, magnetic storms has not yet been clarified. This is because it is necessary to accurately measure the velocity field of the plasma of the filament in order to determine whether the plasma is actually ejected into the interplanetary space. It is impossible to obtain the line of sight velocity field of the filament plasma only by H-alpha line(6562.808 Angstrom), so we use the SDDI (Solar Dynamics Doppler Imager) installed in SMART (Solar Magnetic Activity Research Telescope) in Hida observatory that can take the solar chromospheric full-disk dataset with 0.25 Angstrom step between -9 to +9 Angstrom centered at H-alpha line. In this study, Becker’s “cloud model” is applied to the filament observation at 73 wavelengths and we can get the line of sight velocity. We calculated the line of sight velocities of the filament observed on 2016 August 9th to 10th. This event is occurred at the coordinates (x, y) = (-825,319) around the east limb of the sun and CME was occurred immediately after that. It was possible to track the three dimensional shape change of the filament structure entirely from the pre-ejection stage to the ejection finish by combining the gaze direction velocity field and the visual motion on the AIA images. This filament erupted to 150km/s, the maximum speed from the surface of the sun, and the large CME had occurred to 370km/s in Aug 10th 4:00UT, after the eruption. We traced the time variations of the directions of the filament movement by observing the plasma blobs in the filament in detail. Today, I will report about the time variation of fine structure of the filament.	MB
	main	Y.W. Huang			pdf MB
07-20	short	D. Yamasaki	Signatures of ubiquitous magnetic reconnection in the lower solar atmosphere	Ellerman Bomb-like brightenings of the hydrogen Balmer line wings in the quiet Sun (QSEBs) are a signature of the fundamental process of magnetic reconnection at the smallest observable scale in the solar lower atmosphere. We analyze high spatial resolution observations (0.1 arcsec) obtained with the Swedish 1-m Solar Telescope to explore signatures of QSEBs in the Hβ line. We find that QSEBs are ubiquitous and uniformly distributed throughout the quiet Sun, predominantly occurring in intergranular lanes. We find up to 120 QSEBs in the FOV for a single moment in time; this is more than an order of magnitude higher than the number of QSEBs found in earlier Hα observations. This suggests that about half a million QSEBs could be present in the lower solar atmosphere at any given time. The QSEB brightening found in the Hβ line wings also persist in the line core with a temporal delay and spatial offset towards the nearest solar limb. Our results suggest that QSEBs emanate through magnetic reconnection along vertically extended current sheets in the solar lower atmosphere. The apparent omnipresence of small-scale magnetic reconnection may play an important role in the energy balance of the solar chromosphere. https://ui.adsabs.harvard.edu/abs/2020arXiv200614975J/abstract	pptx MB
	main	D. Seki	Three dimensional velocities of filaments and their CME associations	Coronal Mass Ejections (CMEs) have been paid much attention to as one of the main drivers of geomagnetic storms. Since major geomagnetic storms could bring adverse socioeconomic impacts such as blackouts, the prediction and monitor of CMEs are important. A filament is one of the key proxies to predict CME occurrence because it is widely believed that the core of a CME originates from a filament. In a statistical sense, the CME association of a filament disappearance has been widely studied, but the association rates vary in studies from a few % to ~90%. The aim of this study is to clarify the relationships between some physical parameters of filaments and their CME associations for better prediction of CMEs. Using SMART/SDDI Filament Disappearance Catalogue, we gathered three dimensional velocities, lengths and directions of 23 filaments with their association with CMEs and found that (1) 89% of the filaments whose final radial velocities were negative were not associated with CMEs, (2) using the maximum radial velocity of a filament enables us to predict CME association better than using its apparent velocity, (3) if the product of Vr_max and length of a filament is larger than 1.26*10^6 km^2 s-1, the filament will become a CME with a probability of 90\% and that (4) for 91\% of the CME-associated events, the direction of filament disappearances inclined for less than 45 deg. Our results suggest that it is possible to judge in advance whether a filament eruption will become a CME or not based on its length and its maximum radial velocity and the importance of the three dimensional velocity of a filament in respect of the prediction of its CME association.	pdf MB

Date

Name

Title

Abstract

File

04-20

Long

K. Ichimoto

04-27

Long

A. Asai

05-11

short

Y.W. Huang

In this short presentation, I will introduce the following paper.

Title : Spectro-polarimetric observations at the NVST: I. instrumental polarization calibration and primary measurements

Authors : Jun-Feng Hou, Zhi Xu, Shu Yuan, Yu-Chao Chen, Jian-Guo Peng, Dong-Guang Wang, Jun Xu, Yuan-Yong Deng, Zhen-Yu Jin, Kai-Fan Ji and Zhong Liu

DOI : https://doi.org/10.1088/1674-4527/20/4/45

pdf
MB

main

S. Ueno

Observational activities and a result of our researches in FY2019

This time, I would like to report observational activities and a result of our researches in FY2019, by using presentation slides for the joint meeting planned to be held on Apr-17 and the 4th PSTEP international symposium on Jan-30. Specifically, I introduce use-situation of the Domeless Solar Telescope for this one year, the recent condition of the CHAIN project, and the result of solar UV reproduction using long-term chromospheric (CaII K) full-disk data.

pdf
MB

05-18

short

D. Seki

“SMART/SDDI Filament Disappearance Catalogue”

This paper describes a new “SMART/SDDI Filament Disappearance Catalogue,” in which we listed almost all the filament disappearance events that the Solar Dynamics Doppler Imager (SDDI) has observed since its installation on the Solar Magnetic Activity Research Telescope (SMART) in May 2016. Our aim is to build a database that can help predict the occurrence and severity of coronal mass ejections (CMEs). The catalogue contains miscellaneous information associated with filament disappearance such as flare, CME, active region, three-dimensional trajectory of erupting filaments, detection in Interplanetary Scintillation (IPS), occurrence of interplanetary CME (ICME) and Dst index. We also provide statistical information on the catalogue data.

URL: https://www.kwasan.kyoto-u.ac.jp/observation/event/sddi-catalogue/

(or you can google “sddi catalogue”)

pdf
MB

main

S. Nagata

pptx
MB

05-25

main

H. Isobe

Today I will talk about FIP and i-FIP effects based on following two papers:

"Inverse First Ionization Potential Effects in Giant Solar Flares Found from Earth X-Ray Albedo with Suzaku/XIS” Katsuda, S. et al. (2020) The Astrophysical Journal, Volume 891, Issue 2, id.126

and

"The FIP and Inverse FIP Effects in Solar and Stellar Coronae” Laming J. M. (2015), Living Reviews in Solar Physics, Volume 12, Issue 1, article id. 2

pptx
MB

06-01

main

T.T. Ishii

Today, I would like to introduce SMART/SDDI event report.

https://www.hida.kyoto-u.ac.jp/SMART/SDDI/event_report/

pptx

06-08

short

K. Namekata

In the short talk, I will talk about "Summary of stellar flare observations in 2019 by Seimei Telescope/OISTER".

pdf

main

K. Nishida

In today's solar seminar, I will introduce the following paper:

Tingyu Gou, Rui Liu, Bernhard Kliem, Yuming Wang, and Astrid M. Veronig

The birth of a coronal mass ejection

Science Advances 06 Mar 2019: Vol. 5, no. 3, eaau7004

https://advances.sciencemag.org/content/5/3/eaau7004

pptx

06-15

short

Y. Kotani

In tomorrow's solar seminar, I will introduce the following paper:

Drews, Ainar & Rouppe van der Voort, Luc (2020)

“A multi-diagnostic spectral analysis of penumbral microjets"

https://ui.adsabs.harvard.edu/abs/2020arXiv200502608D/abstract

pptx

main

A. D. Kawamura

"Updates on our CME statistics study: 150-year proxy of geo-effective flares & solar flare frequency”

06-22

short

K. Kihara

I will introduce following paper.

“Inferring Vector Magnetic Fields from Stokes profiles of GST/NIRIS Using a Convolutional Neural Network”

https://ui.adsabs.harvard.edu/abs/2020ApJ...894...70L/abstract

pdf

main

C. Denis

"A fast-filament eruption observed in the H-alpha line by SMART/SDDI: Imaging and spectroscopy diagnostic"

I will report on a filament eruption detected by SMART/SDDI on 2017 April 23. The eruption was observed in a wide spectral window around the H-alpha center. We investigated the dynamics of the filament eruption by applying the Cloud model and also the spectral analysis. The spectral analysis reveals strongly blue-shifted plasma up to -8.0Å from the line center, meaning that erupting material was ejected in direction to the Earth with a velocity of about 365 km/s. On the other hand, the estimated apparent velocity and acceleration at the filament apex, is about 800 km/s and 3.5 km/s2, respectively, which exhibit an exponential-like evolution. In my presentation I will give details of my analysis and also I will show some updates of my calculations.

pdf

06-29

M2 interim report

H. Tanaka

太陽のCaK線撮像分光観測による紫外線放射の推定

太陽活動は、 11 年で極大期と極小期をむかえる周期変動をしており、太陽活動が地球の気候に与える影響について研究されている (宇宙気候学)。太陽紫外線放射は、太陽活動と同期して、可視光 (太陽総放射量) に比べて大きく変動しており、特に地球の電離層に影響を与えている。しかし、紫外線は地上に届かず、人工衛星による観測が必須なので、継続的な観測は 1990 年代以降に限られる。そのため、長期の紫外線放射の変動は明らかにされていない。そこで、紫外線と CaK 線は、どちらも太陽の彩層が起原であり、相関が強いと考えられていることを利用する。 CaK 線は、地上からの過去の観測結果が残されている。 [観測波長幅と観測開始年が、それぞれ京都大学(0.74 Å、 1928 年)、国立天文台 (0.5 Å、 1917 年)、 Kodaikanal(0.5 Å、 1907 年)、 Mt.Wilson(0.2 Å、 1915年)] 本研究では、飛騨天文台ドームレス太陽望遠鏡 (DST) の水平分光器による 2010 年 8 月 22 日、 2012 年 8 月1 日、 2018 年 5 月 5 日の CaK 線の画像データと、人工衛星 SDO の紫外線観測装置 AIA による同日の紫外線 304 Å、 1600 Å、 1700 Åの画像データを用いた。 DST の波長分解能を生かし、 CaK 線の積分する波長幅を変え、どの波長幅が紫外線放射強度と相関がいいのかを調べた。その結果、紫外線の波長が長くなると、相関のいい波長幅は広くなることが分かった。また、波長幅が広いとき、明るい領域では、 CaK 強度の増加に比べて、紫外線強度の増加が大きいことが分かった。輝線や短い波長の紫外線を再現するには、 Mt.Wilson などの波長幅が狭いデータ、長い波長の紫外線を再現するには、Kyoto などの波長幅が広いデータを使う必要があると考えられる。修士論文に向けて、静穏領域と活動領域での違いを調べる、scatter plotの振る舞いの差から分かることを導き出すなどを行いたい

pptx
MB

M2 interim report

Y. Tomino

部分電離プラズマ中で起きる磁気リコネクションの数値的研究

約一万度の太陽彩層には部分電離プラズマが存在し、ジェット現象などの突発的なエネルギー解放現象が頻繁に起こっている。これらの現象のエネルギー解放過程では磁力線のつなぎ替え(磁気リコネクション)が重要な役割を果たし、それに伴って生じる衝撃波がプラズマの運動に大きく影響していると考えられている。そのため、磁気リコネクションで生じる衝撃波や磁場の構造を理解するための数値的研究(例 Yokoyama & Shibata 1998)は以前から行われてきた。また、部分電離プラズマの存在する彩層でのジェット現象に関しても同様に数値計算(例 Martínez-Sykora et al. 2017)によって盛んに研究されてきた。それらの研究では電離成分(イオンと電子)と中性成分(中性粒子)の混在する彩層を簡単のため一流体の電磁流体と近似している。しかし、電離成分と中性成分が混在している彩層を一流体として扱うことの妥当性は十分に検証されていない。実際に部分電離プラズマ中での衝撃波の発展に関して、一流体として計算した場合と二流体(電離成分と中性成分)で計算した場合に磁場の構造や圧力の分布が異なる結果になることが一次元の数値計算では示されている(Snow & Hillier 2019)。本研究では部分電離プラズマ中で磁気リコネクションが起きた際に、一流体で計算した場合と二流体方程式で計算した場合の結果の違いを二次元の数値シミュレーションを用いて調べた。計算の設定はZenitani & Miyoshi (2011)を参考にし、ペチェック型のリコネクションが起きるようにした。結果として電離成分の圧力にのみ衝撃波構造が生じることで、一流体での計算と二流体計算の結果に違いが生まれることが確認された。本発表ではこれまでの結果と今後の修士課程における研究の展望を報告する。

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07-06

short

N. Kimura

Determination of 3D velocity fields of the erupting solar filament on 2016 August 9 using SMART/SDDI at Hida Observatory

Space weather means the environmental changes around the earth due to solar activity. When a flare, explosion on the surface of the sun, occurs, the earth is affected by magnetic storms and increasing radiation and infrastructures are damaged by high energy particles, therefore it is needed to forecast a space weather. In particular, filament eruption and disappearance, the event that cooler plasma floating on the atmosphere of the sun erupt into the interplanetary space, highly related to the coronal mass ejection which is the emission of large amounts of solar plasma into the interplanetary space. It is thought to be one of the reason of magnetic storms, however, the relationship between filament eruption and disappearance, coronal mass ejection, magnetic storms has not yet been clarified. This is because it is necessary to accurately measure the velocity field of the plasma of the filament in order to determine whether the plasma is actually ejected into the interplanetary space. It is impossible to obtain the line of sight velocity field of the filament plasma only by H-alpha line(6562.808 Angstrom), so we use the SDDI (Solar Dynamics Doppler Imager) installed in SMART (Solar Magnetic Activity Research Telescope) in Hida observatory that can take the solar chromospheric full-disk dataset with 0.25 Angstrom step between -9 to +9 Angstrom centered at H-alpha line. In this study, Becker’s “cloud model” is applied to the filament observation at 73 wavelengths and we can get the line of sight velocity. We calculated the line of sight velocities of the filament observed on 2016 August 9th to 10th. This event is occurred at the coordinates (x, y) = (-825,319) around the east limb of the sun and CME was occurred immediately after that. It was possible to track the three dimensional shape change of the filament structure entirely from the pre-ejection stage to the ejection finish by combining the gaze direction velocity field and the visual motion on the AIA images. This filament erupted to 150km/s, the maximum speed from the surface of the sun, and the large CME had occurred to 370km/s in Aug 10th 4:00UT, after the eruption. We traced the time variations of the directions of the filament movement by observing the plasma blobs in the filament in detail. Today, I will report about the time variation of fine structure of the filament.

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Y.W. Huang

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07-20

short

D. Yamasaki

Signatures of ubiquitous magnetic reconnection in the lower solar atmosphere

Ellerman Bomb-like brightenings of the hydrogen Balmer line wings in the quiet Sun (QSEBs) are a signature of the fundamental process of magnetic reconnection at the smallest observable scale in the solar lower atmosphere. We analyze high spatial resolution observations (0.1 arcsec) obtained with the Swedish 1-m Solar Telescope to explore signatures of QSEBs in the Hβ line. We find that QSEBs are ubiquitous and uniformly distributed throughout the quiet Sun, predominantly occurring in intergranular lanes. We find up to 120 QSEBs in the FOV for a single moment in time; this is more than an order of magnitude higher than the number of QSEBs found in earlier Hα observations. This suggests that about half a million QSEBs could be present in the lower solar atmosphere at any given time. The QSEB brightening found in the Hβ line wings also persist in the line core with a temporal delay and spatial offset towards the nearest solar limb. Our results suggest that QSEBs emanate through magnetic reconnection along vertically extended current sheets in the solar lower atmosphere. The apparent omnipresence of small-scale magnetic reconnection may play an important role in the energy balance of the solar chromosphere.

https://ui.adsabs.harvard.edu/abs/2020arXiv200614975J/abstract

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D. Seki

Three dimensional velocities of filaments and their CME associations

Coronal Mass Ejections (CMEs) have been paid much attention to as one of the main drivers of geomagnetic storms. Since major geomagnetic storms could bring adverse socioeconomic impacts such as blackouts, the prediction and monitor of CMEs are important. A filament is one of the key proxies to predict CME occurrence because it is widely believed that the core of a CME originates from a filament. In a statistical sense, the CME association of a filament disappearance has been widely studied, but the association rates vary in studies from a few % to ~90%. The aim of this study is to clarify the relationships between some physical parameters of filaments and their CME associations for better prediction of CMEs. Using SMART/SDDI Filament Disappearance Catalogue, we gathered three dimensional velocities, lengths and directions of 23 filaments with their association with CMEs and found that (1) 89% of the filaments whose final radial velocities were negative were not associated with CMEs, (2) using the maximum radial velocity of a filament enables us to predict CME association better than using its apparent velocity, (3) if the product of Vr_max and length of a filament is larger than 1.26*10^6 km^2 s-1, the filament will become a CME with a probability of 90\% and that (4) for 91\% of the CME-associated events, the direction of filament disappearances inclined for less than 45 deg. Our results suggest that it is possible to judge in advance whether a filament eruption will become a CME or not based on its length and its maximum radial velocity and the importance of the three dimensional velocity of a filament in respect of the prediction of its CME association.

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