総合解析セミナー

総合解析セミナーは基本的に、毎週木曜日の16:30から行われます。
場所は研究所共同館 3階 講義室です。

開催日時 講演者 講演タイトル
4/13 草野 完也 (教授)
Kanya Kusano
Overview of the Integrated Studies Division and the Project for Solar-Terrestrial Environment Prediction (PSTEP)
Abstract : The solar-terrestrial environment is a complex system that consists of nonlinear, non-equilibrium, and multi-scale interacting processes. The research in the Integrated Studies Division aims at improving our understanding of the dynamics of various phenomena in the solar-terrestrial environment through data analyses and modeling studies. The Integrated Studies Division is now playing the leading role for the Project for Solar-Terrestrial Environment Prediction (PSTEP) that is a Japanese-wide research collaborative project aiming to develop a synergistic interaction between predictive and scientific studies of the solar-terrestrial environment and to establish the basis for next-generation space weather forecasting. In this talk, we will talk about the overview of the Integrated Studies Division and the PSTEP, and also discuss about what kind of strategy we should take in order to develop our reseach in future. In particular, I would like to emphasize how important is the interdisciplinary aspect to open up new research based on my personal experience.
4/20 町田 忍 (教授)
Shinobu Machida
Frontier of Substorm Study
Abstract : Since Prof. Akasofu first proposed the concept of substorm in 1964 based on the all-sky auroral network observations on the ground, the study on substorm has been extended to understand the nature and causal relationship of various variations and disturbances appear on the ground, ionosphere and magnetosphere associated with the enhancement of auroral activity. At the same time, the study of the triggering and driving mechanisms of substorm has also progressed, and numbers of substorm models have been proposed so far, but no final conclusion has been obtained yet. Under such circumstances, the recent work done by Fukui et al. [2017] in which the data from THEMIS probes were analyzed, and they found that the spatial gradient of the plasma pressure around X ~ -7.5 Re is nearly 1.4 times higher in substorms compared to the pseudo-substorms around their onsets although the magnetic reconnection occurs in both cases. This result seems to have a primary importance. Also recently, Ebihara and Tanaka [2015] performed a large scale 3D global MHD simulation, and succeeded in reproducing the development of aurora expansion during the substorm in their calculation. Interestingly, their results do not show the occurrence of turbulent oscillations corresponding to the current disruption at the time of auroral expansion. In this sense, the assessment of their model comparing with actual observational data is so significant. In this talk, the status of recent substorm study including those works will be reported.
4/27 松本 琢磨 (研究員)
Matsumoto Takuma
Connecting the Sun and the solar wind: the self-consistent transition of heating mechanisms
Abstract : We have performed a 2.5-dimensional magnetohydrodynamic simulation that resolves the propagation and dissipation of Alfv´en waves in the solar atmosphere. Alfv´enic fluctuations are introduced on the bottom boundary of the extremely large simulation box that ranges from the photosphere to far above the solar wind acceleration region. Our model is ab initio in the sense that no corona and no wind are assumed initially. The numerical experiment reveals the quasi-steady solution that has the transition from the cool to the hot atmosphere and the emergence of the high speed wind. The global structure of the resulting hot wind solution fairly well agrees with the coronal and the solar wind structure inferred from observations. The purpose of this study is to complement the previous paper by Matsumoto & Suzuki and describe the more detailed results and the analysis method. These results include the dynamics of the transition region and the more precisely measured heating rate in the atmosphere. Particularly, the spatial distribution of the heating rate helps us to interpret the actual heating mechanisms in the numerical simulation. Our estimation method of heating rate turned out to be a good measure for dissipation of Alfv´en waves and low beta fast waves.
5/9 金子 岳史 (研究員)
Kaneko Takafumi
Numerical study of solar prominence formation
Abstract: We propose a model in which magnetic reconnection triggers radiative condensation for solar prominence formation and demonstrate it by three-dimensional magnetohydrodynamic (MHD) simulations including anisotropic nonlinear thermal conduction and optically thin radiative cooling. Solar prominences are cool dense plasma clouds in the hot tenuous corona. Prominences have potential to give an impact on the solar-terrestrial plasma environment because they suddenly erupt to interplanetary space and evolve into coronal mass ejections. Not only the mechanism of eruptions, the formation mechanism of prominence is still unclear. We propose a reconnection–condensation model in which the topological change of a coronal magnetic field via reconnection triggers radiative condensation for prominence formation. Previous observational studies suggested that reconnection at a polarity inversion line of a coronal arcade field creates a flux rope sustaining a prominence, however, the origin of the cool dense plasmas of a prominence was not clear. Using three-dimensional MHD simulations including anisotropic nonlinear thermal conduction and optically thin radiative cooling, we demonstrate that reconnection leads not only to flux rope formation but also to radiative condensation under a certain condition. This critical condition in our model is described by the Field length (introduced by George B. Field, 1965), which is defined as the scale length for thermal balance between radiative cooling and thermal conduction. The multi-wavelength extreme ultraviolet emissions synthesized with our simulation results have good agreement with observational signatures in prominence formation events.
5/11 寺本 万里子 (特任助教)
Mariko Teramoto
ULF waves interaction with energetic electron during a relativistic electron loss event
Abstract: During the main phase of a geomagnetic storm, flux decrease in the outer radiation belt. Radial transport of the electron via drift resonance of ULF waves is consider as one important process for this radiation belt losses. We focus on a moderate geomagnetic storm during 13-22 September 2014 which were associated with high speed solar wind (~600 km/s) and strongly northward IMF. The electron flux level in the outer zone with energy raging from 1 MeV to 5.6 MeV decreased on stating 12 September 2014. We compared the disturbance in the flux of the electron with ULF waves in the magnetic filed data from the Van Allen Probes and estimated the electron resonant energies, which indicate strong drift resonant interaction occurring between the energetic electron and the ULF waves. We found that the resonant energy is much lower than the relativistic electron associated with the losses in the outer belt. We conclude that ULF waves might not play a key role of outward diffusion of electron to help drive radiation belt losses in this event.
5/18 井上 諭 (特任助教)
Inoue Satoshi
Formation and Dynamics of Solar Eruptive Flux Tube.
Abstract: We perform a magnetohydrodynamic simulation to reveal the dynamics of the solar eruption accompanied with M6.6 class flare observed in the solar active region 11158. In order to shorten a distance between the theoretical models and observations, our simulation takes into account the observed photospheric magnetic field from which a non-linear force-free field is reconstructed to employ the initial state. In our simulation we confirmed that the tether-cutting reconnection occurring locally above the polarity inversion line makes twisted flux tube which destroys the equilibrium magnetic field and drives the eruption. Then the eruption, surprisingly, can be driven even in the stable area of the torus instability. We suggested that the reconnection between the twisted lines during the eruption is essential to make more highly twisted flux tube which further drives away from the equilibrium state. Then the dynamics is no longer controlled by the decay index, rather by its nonlinear process.
6/1 家田 章正 (助教)
Akimasa Ieda
6/6 伊集 朝哉 (研究員)
Tomoya Iju
6/8 神谷 慶 (D2)
Kei Kamiya
6/15 Jie Ren (研究員)
6/22 石黒 直行 (D2)
Naoyuki Ishiguro
6/29 Muhamad Johan (D2)
7/6 柴山 拓也 (D2)
Takuya Shibayama
7/13 Inchun Park (D2)
7/20 三谷 憲司 (D2)
Kenji Mitani
7/27 小山 響平 (D3)
Kyohei Koyama
9/7 三好 由純 (准教授)
Yoshizumi Miyoshi
9/14 堀 智昭 (特任准教授)
Tomoaki Hori
9/19 川嶋 貴大 (M2)
Takahiro Kawashima
9/21 旭 友希 (M2)
Yuuki Asahi
9/28 藤山 雅士 (M2)
Masashi Fujiyama
10/3 水野 雄太 (M2)
Yuta Mizuno
10/5 三浦 翼 (M2)
Tsubasa Miura
10/12 與那覇 公泰 (M2)
Kimiyasu Yonaha
10/26 淺野 貴紀 (M2)
Takaki Asano
11/2 上村 亮弥 (M2)
Ryoya Uemura
11/9 林 昌広 (M2)
Masahiro Hayashi
11/16 福井 健人(M2)
Kento Fukui
11/21 増田 智 (准教授)
Satoshi Masuda
11/30 梅田 隆行 (講師)
Takayuki Umeda
12/5 近藤 克哉 (M1)
Katsuya Kondo
12/7 箕浦 桜子 (M1)
Sakurako Minoura
12/21 小林 勇貴 (M1)
Yuuki Kobayashi
1/11 小路 真史 (特任助教)
Masafumi Shoji
1/18 飯島 陽久(研究員)
Haruhisa Iijima
1/23 Sung-Hong Park(研究員)
1/25 松田 昇也 (研究員)
Shoya Matsuda
2/1 齊藤 慎司 (特任助教)
Shinji Saito
2/6 Tzu-Fang Chang(特任助教)
2/8 栗田 怜 (研究員)
Satoshi Kurita
2/15 今田 晋亮 (助教)
Shinsuke Imada
2/22 津川 靖基(研究員)
Yasunori Tsugawa