30 results on '"Takayoshi Sano"'
Search Results
2. Hugoniot and released state of calcite above 200 GPa with implications for hypervelocity planetary impacts
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Yuhei Umeda, Keiya Fukui, Toshimori Sekine, Marco Guarguaglini, Alessandra Benuzzi-Mounaix, Nobuki Kamimura, Kento Katagiri, Ryosuke Kodama, Takeshi Matsuoka, Kohei Miyanishi, Alessandra Ravasio, Takayoshi Sano, Norimasa Ozaki, Osaka University, Okayama University, Kyoto University, Laboratoire pour l'utilisation des lasers intenses (LULI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), RIKEN SPring-8 Center [Hyogo] (RIKEN RSC), and RIKEN - Institute of Physical and Chemical Research [Japon] (RIKEN)
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Space and Planetary Science ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,Astronomy and Astrophysics - Abstract
International audience; Carbonate minerals, for example calcite and magnesite, exist on the planetary surfaces of the Earth, Mars, and Venus, and are subjected to hypervelocity collisions. The physical properties of planetary materials at extreme conditions are essential for understanding their dynamic behaviors at hypervelocity collisions and the mantle structure of rocky planets including Super-Earths. Here we report laboratory investigations of laser-shocked calcite at pressures of 200-960 GPa (impact velocities of 12-30 km/s and faster than escape velocity from the Earth) using decay shock techniques. Our measured temperatures above 200 GPa indicated a large difference from the previous theoretical models. The present shock Hugoniot data and temperature measurements, compared with the previous reports, indicate melting without decomposition at pressures of ~110 GPa to ~350 GPa and a bonded liquid up to 960 GPa from the calculated specific heat. Our temperature calculations of calcite at 1 atm adiabatically released from the Hugoniot points suggest that the released products vary depending on the shock pressures and affect the planetary atmosphere by the degassed species. The present results on calcite newly provide an important anchor for considering the theoretical EOS at the extreme conditions, where the model calculations show a significant diversity at present.
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- 2022
3. Laser astrophysics experiment on the amplification of magnetic fields by shock-induced interfacial instabilities
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Michel Koenig, Youichi Sakawa, P. Mabey, Bruno Albertazzi, Masakatsu Murakami, Takayoshi Sano, M. Ota, Seung Ho Lee, R. Kumar, S. Egashira, Kazuki Matsuo, Alexis Casner, Taichi Morita, Shohei Tamatani, Y. Hara, Keisuke Shigemori, Shinsuke Fujioka, Shohei Sakata, Thibault Michel, H. Shimogawara, G. Rigon, King Fai Farley Law, Research Applications Laboratory [Boulder] (RAL), National Center for Atmospheric Research [Boulder] (NCAR), Laboratoire pour l'utilisation des lasers intenses (LULI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Lasers Intenses et Applications (CELIA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB), and Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)
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FOS: Physical sciences ,7. Clean energy ,01 natural sciences ,Instability ,010305 fluids & plasmas ,law.invention ,law ,0103 physical sciences ,010306 general physics ,ComputingMilieux_MISCELLANEOUS ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,[PHYS]Physics [physics] ,Turbulence ,Plasma ,Laser ,Physics - Plasma Physics ,[PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph] ,Shock (mechanics) ,Magnetic field ,Computational physics ,Plasma Physics (physics.plasm-ph) ,Interstellar medium ,Supernova ,13. Climate action ,Astrophysics - High Energy Astrophysical Phenomena ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] - Abstract
Laser experiments are becoming established as a new tool for astronomical research that complements observations and theoretical modeling. Localized strong magnetic fields have been observed at a shock front of supernova explosions. Experimental confirmation and identification of the physical mechanism for this observation are of great importance in understanding the evolution of the interstellar medium. However, it has been challenging to treat the interaction between hydrodynamic instabilities and an ambient magnetic field in the laboratory. Here, we developed an experimental platform to examine magnetized Richtmyer-Meshkov instability (RMI). The measured growth velocity was consistent with the linear theory, and the magnetic-field amplification was correlated with RMI growth. Our experiment validated the turbulent amplification of magnetic fields associated with the shock-induced interfacial instability in astrophysical conditions for the first time. Experimental elucidation of fundamental processes in magnetized plasmas is generally essential in various situations such as fusion plasmas and planetary sciences., 17 pages, 12 figures, 3 tables, accepted for publication in PRE
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- 2021
4. Nonlinear interfacial motion in magnetohydrodynamic flows
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Katsunobu Nishihara, Takayoshi Sano, and Chihiro Matsuoka
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Physics ,Convection ,Nuclear and High Energy Physics ,Radiation ,Magnetic energy ,電磁流体 ,Mechanics ,Instability ,Magnetic field ,Vortex ,Physics::Fluid Dynamics ,リヒトマイヤー・メシュコフ不安定性 ,Physics::Plasma Physics ,Vortex sheet ,Physics::Space Physics ,電流渦層 ,Astrophysics::Solar and Stellar Astrophysics ,ケルビン・ヘルムホルツ不安定性 ,Current-vortex sheet ,Magnetohydrodynamic drive ,Magnetohydrodynamics ,MHD Richtmyer–Meshkov instability ,MHD Kelvin–Helmholtz instability - Abstract
Nonlinear motion of vortex sheets with non-uniform current is investigated taking the magnetohydrodynamic Richtmyer–Meshkov instability (MHD RMI) and the magnetohydrodynamic Kelvin–Helmholtz instability (MHD KHI) as the examples. As the ratio of the magnetic force to the convective force increases, Alfven oscillations appear and the nonlinear growth of the interface as a vortex sheet is suppressed. We show that the turbulent energy possessing the interface flows into the magnetic energy, which causes the strong magnetic field amplification for both instabilities. We also discuss the difference of the temporal evolution of the interface between MHD RMI and MHD KHI.
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- 2019
5. Rayleigh-Taylor instability experiments on the LULI2000 laser in scaled conditions for young supernova remnants
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Norimasa Ozaki, Alexis Casner, G. Rigon, J. Ballet, S. A. Pikuz, Yasuhiro Kuramitsu, Bruno Albertazzi, M. P. Valdivia, A. Faenov, D. Q. Lamb, Petros Tzeferacos, Emeric Falize, Tatiana Pikuz, Takayoshi Sano, Yoichi Sakawa, P. Mabey, M. Koenig, L. Van Box Som, Th. Michel, Laboratoire pour l'utilisation des lasers intenses (LULI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Lasers Intenses et Applications (CELIA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB), University of Oxford [Oxford], Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Joint Institute for High Temperatures of the RAS (JIHT), Russian Academy of Sciences [Moscow] (RAS), Institute of laser Engineering, Osaka University [Osaka], Japan Atomic Energy Agency, Graduate School of Engineering, Department of Physics [Oxford], Department of Mathematics [Jeddah], King Abdulaziz University, ANR-15-CE30-0011, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Graduate School of Engineering [Suita, Osaka], Osaka University, Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn] ,Astrophysics::High Energy Astrophysical Phenomena ,Resolution (electron density) ,Astrophysics ,Laser ,01 natural sciences ,Instability ,010305 fluids & plasmas ,law.invention ,Supernova ,law ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,0103 physical sciences ,Radiative transfer ,[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex] ,Rayleigh–Taylor instability ,010306 general physics - Abstract
International audience; We describe a platform developed on the LULI2000 laser facility to investigate the evolution of Rayleigh-Taylor instability (RTI) in scaled conditions relevant to young Supernovae Remnant (SNR) up to 200 years. An RT unstable interface is imaged with a short-pulse laser-driven (PICO2000) x-ray source, providing an unprecedented simultaneous high spatial (24 µm) and temporal (10 ps) resolution. This experiment provides relevant data to compare with astrophysical codes, as observational data on the development of RTI at the early stage of the SNR expansion are missing. A comparison is also performed with FLASH radiative magneto-hydrodynamic simulations.
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- 2019
6. From ICF to laboratory astrophysics: ablative and classical Rayleigh–Taylor instability experiments in turbulent-like regimes
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Igor V. Igumenshchev, N. Izumi, D. Q. Lamb, Shahab Khan, G. Rigon, Laurent Masse, J. M. Di Nicola, Vladimir Tikhonchuk, J. Ballet, Takayoshi Sano, C. Mailliet, P. Di Nicola, Youichi Sakawa, David Martinez, S. Liberatore, V. A. Smalyuk, E. Le Bel, Emeric Falize, T. Michel, M. Koenig, Bruno Albertazzi, Daniel H. Kalantar, Petros Tzeferacos, Bruce Remington, Alexis Casner, Centre d'Etudes Lasers Intenses et Applications (CELIA), Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire pour l'utilisation des lasers intenses (LULI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ANR-15-CE30-0011,TurbOHEDP,Expériences d'Hydrodynamique turbulente dans des plasmas denses et chauds(2015), and Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB)
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Physics ,Nuclear and High Energy Physics ,Turbulence ,Visible radiation ,Condensed Matter Physics ,01 natural sciences ,Electromagnetic radiation ,Instability ,010305 fluids & plasmas ,Computational physics ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,0103 physical sciences ,Ablative case ,Energy density ,Rayleigh–Taylor instability ,010306 general physics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2019
7. Laser-driven shock compression of 'synthetic planetary mixtures' of water, ethanol, and ammonia
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Ryosuke Kodama, Alessandra Ravasio, J.-A. Hernandez, Norimasa Ozaki, Kohei Miyanishi, M. Koenig, Alessandra Benuzzi-Mounaix, Martin French, Takayoshi Sano, Erik Brambrink, Yasunori Fujimoto, R. Bolis, Yuhei Umeda, F. Lefevre, Mandy Bethkenhagen, Takuo Okuchi, P. Barroso, Tommaso Vinci, Ronald Redmer, M. Guarguaglini, Laboratoire pour l'utilisation des lasers intenses (LULI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut Polytechnique de Paris (IP Paris), Okayama University, Observatoire de Paris, Université Paris sciences et lettres (PSL), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Universität Rostock, Institut für Physik [Rostock], Osaka University [Osaka], ANR POMPEI (Grant No. ANR-16-CE31-0008), and ANR-16-CE31-0008,POMPEI,Propriétés de Mélanges de H2ONH3CH4 d'interet pour les intérieurs planétaires et les exoplanètes.(2016)
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0301 basic medicine ,Materials science ,Thermodynamic state ,Chemical physics ,Science ,Article ,03 medical and health sciences ,0302 clinical medicine ,Neptune ,Planet ,Giant planets ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,Adiabatic process ,Multidisciplinary ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,Exoplanets ,Uranus ,Laser-produced plasmas ,Computational physics ,Shock (mechanics) ,Boundary layer ,030104 developmental biology ,13. Climate action ,Medicine ,Astrophysics::Earth and Planetary Astrophysics ,030217 neurology & neurosurgery ,Ice giant - Abstract
Water, methane, and ammonia are commonly considered to be the key components of the interiors of Uranus and Neptune. Modelling the planets’ internal structure, evolution, and dynamo heavily relies on the properties of the complex mixtures with uncertain exact composition in their deep interiors. Therefore, characterising icy mixtures with varying composition at planetary conditions of several hundred gigapascal and a few thousand Kelvin is crucial to improve our understanding of the ice giants. In this work, pure water, a water-ethanol mixture, and a water-ethanol-ammonia “synthetic planetary mixture” (SPM) have been compressed through laser-driven decaying shocks along their principal Hugoniot curves up to 270, 280, and 260 GPa, respectively. Measured temperatures spanned from 4000 to 25000 K, just above the coldest predicted adiabatic Uranus and Neptune profiles (3000–4000 K) but more similar to those predicted by more recent models including a thermal boundary layer (7000–14000 K). The experiments were performed at the GEKKO XII and LULI2000 laser facilities using standard optical diagnostics (Doppler velocimetry and optical pyrometry) to measure the thermodynamic state and the shock-front reflectivity at two different wavelengths. The results show that water and the mixtures undergo a similar compression path under single shock loading in agreement with Density Functional Theory Molecular Dynamics (DFT-MD) calculations using the Linear Mixing Approximation (LMA). On the contrary, their shock-front reflectivities behave differently by what concerns both the onset pressures and the saturation values, with possible impact on planetary dynamos.
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- 2019
8. Magnetic reconnection driven by electron dynamics
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Youichi Sakawa, Takayoshi Sano, Christopher D. Gregory, Shuichi Matsukiyo, Y. L. Liu, Toseo Moritaka, Taichi Morita, Hideaki Takabe, Yasuhiro Kuramitsu, M. Koenig, Masahiro Hoshino, Kentaro Tomita, Nigel Woolsey, Shih Hung Chen, Osaka University [Osaka], National Central University [Taiwan] (NCU), Laboratoire pour l'utilisation des lasers intenses (LULI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), University of York [York, UK], Kyushu University [Fukuoka], The University of Tokyo (UTokyo), and Kyushu University
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Astrophysical plasmas ,Science ,General Physics and Astronomy ,Plasmoid ,Electron ,01 natural sciences ,7. Clean energy ,Article ,General Biochemistry, Genetics and Molecular Biology ,010305 fluids & plasmas ,Ion ,Physics::Plasma Physics ,[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph] ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Magnetic pressure ,lcsh:Science ,010306 general physics ,Physics ,Solar physics ,Multidisciplinary ,Magnetic energy ,Magnetic reconnection ,General Chemistry ,Plasma ,Laser-produced plasmas ,equipment and supplies ,[PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,Computational physics ,Magnetic field ,Physics::Space Physics ,Magnetospheric physics ,lcsh:Q ,human activities - Abstract
Magnetic reconnections play essential roles in space, astrophysical, and laboratory plasmas, where the anti-parallel magnetic field components re-connect and the magnetic energy is converted to the plasma energy as Alfvénic out flows. Although the electron dynamics is considered to be essential, it is highly challenging to observe electron scale reconnections. Here we show the experimental results on an electron scale reconnection driven by the electron dynamics in laser-produced plasmas. We apply a weak-external magnetic field in the direction perpendicular to the plasma propagation, where the magnetic field is directly coupled with only the electrons but not for the ions. Since the kinetic pressure of plasma is much larger than the magnetic pressure, the magnetic field is distorted and locally anti-parallel. We observe plasma collimations, cusp and plasmoid like features with optical diagnostics. The plasmoid propagates at the electron Alfvén velocity, indicating a reconnection driven by the electron dynamics., Magnetic reconnection is the process of releasing energy by magnetized and space plasma. Here the authors report experimental observation of magnetic reconnection in laser-produced plasma and the role of electron scaling on reconnection.
- Published
- 2018
9. Spontaneous Formation of Surface Magnetic Structure from Large-scale Dynamo in Strongly-stratified Convection
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Takayoshi Sano and Youhei Masada
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Convection ,Convective heat transfer ,FOS: Physical sciences ,01 natural sciences ,Atmosphere ,Physics::Fluid Dynamics ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010306 general physics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Physics ,Sunspot ,Magnetic structure ,Fluid Dynamics (physics.flu-dyn) ,Astronomy and Astrophysics ,Mechanics ,Physics - Fluid Dynamics ,equipment and supplies ,Physics - Plasma Physics ,Magnetic field ,Plasma Physics (physics.plasm-ph) ,Convection zone ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,human activities ,Dynamo - Abstract
We report the first successful simulation of spontaneous formation of surface magnetic structures from a large-scale dynamo by strongly-stratified thermal convection in Cartesian geometry. The large-scale dynamo observed in our strongly-stratified model has physical properties similar to those in earlier weakly-stratified convective dynamo simulations, indicating that the $\alpha^2$-type mechanism is responsible for it. Additionally to the large-scale dynamo, we find that large-scale structures of the vertical magnetic field are spontaneously formed in the convection zone surface only for the case of strongly-stratified atmosphere. The organization of the vertical magnetic field proceeds in the upper convection zone within tens of convective turn-over time and band-like bipolar structures are recurrently-appeared in the dynamo-saturated stage. We examine possibilities of several candidates as the origin of the surface magnetic structure formation, and then suggest the existence of an as-yet-unknown mechanism for the self-organization of the large-scale magnetic structure, which should be inherent in the strongly-stratified convective atmosphere., Comment: Accepted for Publication in ApJ Letters (7 pages, 5 figure)
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- 2016
10. Spherical shock in the presence of an external magnetic field
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H. Takabe, R. Shimoda, Kazunori Nagamine, Jiayong Zhong, A. Pelka, R. Fujino, Yuta Yamaura, Naofumi Ohnishi, Shogo Isayama, Nigel Woolsey, R. Crowston, Kiichiro Uchino, Taichi Morita, T. Ishikawa, Kentaro Tomita, Y. T. Li, C. L. Yin, Youichi Sakawa, D. Harada, Hisao Yoneda, Shuichi Matsukiyo, Fudi Wang, Yasuhiro Kuramitsu, Yuta Sato, Gianluca Gregori, Toseo Moritaka, Takayoshi Sano, Kai Zhang, M. Koenig, Dawei Yuan, and T. Oyama
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Physics ,History ,Shock (fluid dynamics) ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics ,Plasma ,Shadowgraphy ,equipment and supplies ,Computer Science Applications ,Education ,Magnetic field ,Stellar wind ,Supernova ,Solar wind ,Physics::Plasma Physics ,Physics::Space Physics ,Anisotropy ,human activities ,Astrophysics::Galaxy Astrophysics - Abstract
We investigate spherical collisionless shocks in the presence of an external magnetic field. Spherical collisionless shocks are common resultant of interactions between a expanding plasma and a surrounding plasma, such as the solar wind, stellar winds, and supernova remnants. Anisotropies often observed in shock propagations and their emissions, and it is widely believed a magnetic field plays a major role. Since the local observations of magnetic fields in astrophysical plasmas are not accessible, laboratory experiments provide unique capability to investigate such phenomena. We model the spherical shocks in the universe by irradiating a solid spherical target surrounded by a plasma in the presence of a magnetic field. We present preliminary results obtained by shadowgraphy.
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- 2016
11. Magnetic Coupling in the Disks Around Young Gas Giant Planets
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Neal J. Turner, Takayoshi Sano, and Man Hoi Lee
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Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,Ambipolar diffusion ,Gas giant ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Plasma ,Accretion (astrophysics) ,Atmosphere ,Space and Planetary Science ,Planet ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Magnetohydrodynamics ,Formation and evolution of the Solar System ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We examine the conditions under which the disks of gas and dust orbiting young gas giant planets are sufficiently conducting to experience turbulence driven by the magneto-rotational instability. By modeling the ionization and conductivity in the disk around proto-Jupiter, we find that turbulence is possible if the X-rays emitted near the Sun reach the planet's vicinity and either (1) the gas surface densities are in the range of the minimum-mass models constructed by augmenting Jupiter's satellites to Solar composition, while dust is depleted from the disk atmosphere, or (2) the surface densities are much less, and in the range of gas-starved models fed with material from the Solar nebula, but not so low that ambipolar diffusion decouples the neutral gas from the plasma. The results lend support to both minimum-mass and gas-starved models of the protojovian disk: (1) The dusty minimum-mass models have internal conductivities low enough to prevent angular momentum transfer by magnetic forces, as required for the material to remain in place while the satellites form. (2) The gas-starved models have magnetically-active surface layers and a decoupled interior "dead zone". Similar active layers in the Solar nebula yield accretion stresses in the range assumed in constructing the circumjovian gas-starved models. Our results also point to aspects of both classes of models that can be further developed. Non-turbulent minimum-mass models will lose dust from their atmospheres by settling, enabling gas to accrete through a thin surface layer. For the gas-starved models it is crucial to learn whether enough stellar X-ray and ultraviolet photons reach the circumjovian disk. Additionally the stress-to-pressure ratio ought to increase with distance from the planet, likely leading to episodic accretion outbursts., 35 pages, 8 figures. Chemical network description expanded in sec. 4.1. Turbulent mixing discussion reorganized in secs. 6.3-6.4. Accepted to ApJ
- Published
- 2013
12. Laboratory investigations on the origins of cosmic rays
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Yt T. Li, H. Aoki, Jie Zhang, T. Ide, M. Koenig, S. Dono, K. Mima, Nigel Woolsey, A. Pelka, H. Tanji, Yosuke Matsumoto, Ka A. Tanaka, Jy Y. Zhong, Taichi Morita, Toseo Moritaka, Kotaro Kondo, Yoichi Sakawa, Sa A. Pikuz, Yasuhiro Kuramitsu, Gianluca Gregori, Cd D. Gregory, Hideaki Takabe, Eisuke Miura, A. Diziere, Takayoshi Sano, Yoshitaka Mori, Y. Kitagawa, Alessandra Ravasio, Masahiro Hoshino, Nobuhiko Nakanii, Yi Zhang, K. Nishio, Hiroshi Azechi, Akira Mizuta, Naofumi Ohnishi, Ryosuke Kodama, Berenice Loupias, Jn N. Waugh, and Xianjie Liu
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Physics ,Shock wave ,High power lasers ,media_common.quotation_subject ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy ,Cosmic ray ,Transport theory ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Condensed Matter Physics ,Universe ,Shock waves in astrophysics ,Particle acceleration ,Nuclear Energy and Engineering ,Astrophysical Phenomena ,media_common - Abstract
We report our recent efforts on the experimental investigations related to the origins of cosmic rays. The origins of cosmic rays are long standing open issues in astrophysics. The galactic and extragalactic cosmic rays are considered to be accelerated in non-relativistic and relativistic collisionless shocks in the universe, respectively. However, the acceleration and transport processes of the cosmic rays are not well understood, and how the collisionless shocks are created is still under investigation. Recent high-power and high-intensity laser technologies allow us to simulate astrophysical phenomena in laboratories. We present our experimental results of collisionless shock formations in laser-produced plasmas. © 2012 IOP Publishing Ltd.
- Published
- 2012
13. Magnetic Field Amplification Associated with the Richtmyer-Meshkov Instability
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Takayoshi Sano, Tsuyoshi Inoue, Katsunobu Nishihara, and Chihiro Matsuoka
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Shock (fluid dynamics) ,Field (physics) ,Richtmyer–Meshkov instability ,FOS: Physical sciences ,Astronomy and Astrophysics ,Instability ,Physics - Plasma Physics ,Computational physics ,Magnetic field ,Plasma Physics (physics.plasm-ph) ,symbols.namesake ,Mach number ,Space and Planetary Science ,Computer Science::Multimedia ,symbols ,Magnetic pressure ,Magnetohydrodynamics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
The amplification of a magnetic field due to the Richtmyer-Meshkov instability (RMI) is investigated by two-dimensional MHD simulations. Single-mode analysis is adopted to reveal definite relation between the nonlinear evolution of RMI and the field enhancement. It is found that an ambient magnetic field is stretched by fluid motions associated with the RMI, and the strength is amplified significantly by more than two orders of magnitude. The saturation level of the field is determined by a balance between the amplified magnetic pressure and the thermal pressure after shock passage. This effective amplification can be achieved in a wide range of the conditions for the RMI such as the Mach number of an incident shock and the density ratio at a contact discontinuity. The results suggest that the RMI could be a robust mechanism of the amplification of interstellar magnetic fields and cause the origin of localized strong fields observed at the shock of supernova remnants., 16 pages, 9 figures, accepted for publication in ApJ
- Published
- 2012
14. Axisymmetric Magnetorotational Instability in Viscous Accretion Disks
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Youhei Masada and Takayoshi Sano
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Physics ,Magnetic energy ,Condensed matter physics ,Turbulence ,Astrophysics (astro-ph) ,Reynolds number ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Physics::Fluid Dynamics ,symbols.namesake ,Space and Planetary Science ,Magnetorotational instability ,symbols ,Lundquist number ,Magnetic Prandtl number ,Magnetic diffusivity ,Energy (signal processing) - Abstract
Axisymmetric magnetorotational instability (MRI) in viscous accretion disks is investigated by linear analysis and two-dimensional nonlinear simulations. The linear growth of the viscous MRI is characterized by the Reynolds number defined as $R_{\rm MRI} \equiv v_A^2/\nu\Omega $, where $v_A$ is the Alfv{\'e}n velocity, $\nu$ is the kinematic viscosity, and $\Omega$ is the angular velocity of the disk. Although the linear growth rate is suppressed considerably as the Reynolds number decreases, the nonlinear behavior is found to be almost independent of $R_{\rm MRI}$. At the nonlinear evolutionary stage, a two-channel flow continues growing and the Maxwell stress increases until the end of calculations even though the Reynolds number is much smaller than unity. A large portion of the injected energy to the system is converted to the magnetic energy. The gain rate of the thermal energy, on the other hand, is found to be much larger than the viscous heating rate. Nonlinear behavior of the MRI in the viscous regime and its difference from that in the highly resistive regime can be explained schematically by using the characteristics of the linear dispersion relation. Applying our results to the case with both the viscosity and resistivity, it is anticipated that the critical value of the Lundquist number $S_{\rm MRI} \equiv v_A^2/\eta\Omega$ for active turbulence depends on the magnetic Prandtl number $S_{{\rm MRI},c} \propto Pm^{1/2}$ in the regime of $Pm \gg 1$ and remains constant when $Pm \ll 1$, where $Pm \equiv S_{\rm MRI}/R_{\rm MRI} = \nu/\eta$ and $\eta$ is the magnetic diffusivity., Comment: Accepted for publication in ApJ -- 18 pages, 9 figures, 1 table
- Published
- 2008
15. Turbulent Mixing and the Dead Zone in Protostellar Disks
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Neal J. Turner, N. Dziourkevitch, and Takayoshi Sano
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Physics ,Turbulence ,Astrophysics (astro-ph) ,Stratification (water) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Cosmic ray ,Astrophysics ,Molecular physics ,Magnetic field ,Space and Planetary Science ,Electrical resistivity and conductivity ,Ionization ,Magnetorotational instability ,Astrophysics::Earth and Planetary Astrophysics ,Magnetohydrodynamics ,Astrophysics::Galaxy Astrophysics - Abstract
We investigate the conditions for the presence of a magnetically inactive dead zone in protostellar disks, using 3-D shearing-box MHD calculations including vertical stratification, Ohmic resistivity and time-dependent ionization chemistry. Activity driven by the magnetorotational instability fills the whole thickness of the disk at 5 AU, provided cosmic ray ionization is present, small grains are absent and the gas-phase metal abundance is sufficiently high. At 1 AU the larger column density of 1700 g/cm^2 means the midplane is shielded from ionizing particles and remains magnetorotationally stable even under the most favorable conditions considered. Nevertheless the dead zone is effectively eliminated. Turbulence mixes free charges into the interior as they recombine, leading to a slight coupling of the midplane gas to the magnetic fields. Weak, large-scale radial fields diffuse to the midplane where they are sheared out to produce stronger azimuthal fields. The resulting midplane accretion stresses are just a few times less than in the surface layers on average., to appear in the Astrophysical Journal; 25 pages, 10 figures
- Published
- 2006
16. Nonaxisymmetric Magnetorotational Instability in Proto-Neutron Stars
- Author
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Hideaki Takabe, Youhei Masada, and Takayoshi Sano
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Physics ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Angular velocity ,Astrophysics ,Instability ,Computational physics ,Magnetic field ,Neutron star ,Stars ,Space and Planetary Science ,Magnetorotational instability ,Wavenumber ,Astrophysics::Solar and Stellar Astrophysics ,Magnetohydrodynamics - Abstract
We investigate the stability of differentially rotating proto-neutron stars (PNSs) with a toroidal magnetic field. Stability criteria for nonaxisymmetric MHD instabilities are derived using a local linear analysis. PNSs are expected to have much stronger radial shear in the rotation velocity compared to normal stars. We find that nonaxisymmetric magnetorotational instability (NMRI) with a large azimuthal wavenumber $m$ is dominant over the kink mode ($m=1$) in differentially rotating PNSs. The growth rate of the NMRI is of the order of the angular velocity $\Omega$ which is faster than that of the kink-type instability by several orders of magnitude. The stability criteria are analogous to those of the axisymmetric magnetorotational instability with a poloidal field, although the effects of leptonic gradients are considered in our analysis. The NMRI can grow even in convectively stable layers if the wavevectors of unstable modes are parallel to the restoring force by the Brunt-V\"ais\"al\"a oscillation. The nonlinear evolution of NMRI could amplify the magnetic fields and drive MHD turbulence in PNSs, which may lead to enhancement of the neutrino luminosity., Comment: 24pages, 7figures, Accepted for publication in the Astrophysical Journal (December 12, 2005)
- Published
- 2005
17. Dynamic X-ray diffraction observation of shocked solid iron up to 170 GPa.
- Author
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Denoeud, Adrien, Norimasa Ozaki, Benuzzi-Mounaix, Alessandra, Hiroyuki Uranishi, Yoshihiko Kondo, Ryosuke Kodama, Brambrink, Erik, Ravasio, Alessandra, Bocoum, Maimouna, Boudenne, Jean-Michel, Harmand, Marion, Guyot, François, Mazevet, Stephane, Riley, David, Makita, Mikako, Takayoshi Sano, Youichi Sakawa, Yuichi Inubushi, Gregori, Gianluca, and Koenig, Michel
- Subjects
X-ray diffraction ,SEISMOLOGY ,MAGNETIC fields ,POLYCRYSTALS ,VELOCIMETRY - Abstract
Investigation of the iron phase diagram under high pressure and temperature is crucial for the determination of the composition of the cores of rocky planets and for better understanding the generation of planetary magnetic fields. Here we present X-ray diffraction results from laser-driven shock-compressed single-crystal and polycrystalline iron, indicating the presence of solid hexagonal close-packed iron up to pressure of at least 170 GPa along the principal Hugoniot, corresponding to a temperature of 4,150 K. This is confirmed by the agreement between the pressure obtained from the measurement of the iron volume in the sample and the inferred shock strength from velocimetry deductions. Results presented in this study are of the first importance regarding pure Fe phase diagram probed under dynamic compression and can be applied to study conditions that are relevant to Earth and super-Earth cores. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
18. Impact experiments with a new technique for acceleration of projectiles to velocities higher than Earth's escape velocity of 11.2 km/s
- Author
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Ryosuke Kodama, Toshihiko Kadono, Yasuhito Sekine, T. Fujiwara, Norimasa Ozaki, A. Shiroshita, Seiji Sugita, Keisuke Shigemori, Sohsuke Ohno, Shinsuke Fujioka, W. Nishikanbara, Masahiko Arakawa, Kazuto Otani, T. Matsui, T. Sakaiya, Y. Hironaka, Takayoshi Sano, Kohei Miyanishi, Akiko M. Nakamura, Kosuke Kurosawa, and T. Mochiyama
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Physics ,Atmospheric Science ,Ecology ,business.industry ,Projectile ,Streak camera ,Streak ,Paleontology ,Soil Science ,Forestry ,Escape velocity ,Aquatic Science ,Oceanography ,Geophysics ,Optics ,Impact crater ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Hypervelocity ,Terrestrial planet ,Emission spectrum ,business ,Earth-Surface Processes ,Water Science and Technology - Abstract
[1] The impact velocities of asteroids on Earth and other terrestrial planets can be greater than 10 km/s, and impacts at these high velocities can produce significant effects on the planetary surfaces. However, since macroscopic (>∼0.1 mm) projectiles with an aspect ratio of ∼1 are not easily accelerated to more than 10 km/s in laboratories, there are few detailed experimental studies. In this paper, we demonstrate that impact velocities greater than 10 km/s can be achieved with glass and aluminum projectiles of 0.1–0.3 mm in diameter using a high-power laser, GEKKO XII-HIPER at Institute of Laser Engineering, Osaka University. The velocity of the projectiles is estimated based on the images taken by high-speed X-ray streak and framing cameras. Projectiles collide into copper or LiF plate targets. The copper plates are recovered for analysis. The sizes of craters on the copper plates are not far from the extrapolations from previous work with lower velocities. A tantalum witness plate placed near the copper plates records a large number of secondary craters from each impact. In the case of the impacts of the LiF plates, we observe two emission lines of Li gas using a spectrometer with a streak camera. Thus, we can simulate the hypervelocity impacts with velocities higher than 10 km/s in laboratories.
- Published
- 2010
19. Critical Magnetic Field Strength for Suppression of the Richtmyer-Meshkov Instability in Plasmas.
- Author
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Takayoshi Sano, Tsuyoshi Inoue, and Katsunobu Nishihara
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CRITICAL magnetic field , *VORTEX motion , *RICHTMYER-Meshkov instability , *MAGNETOHYDRODYNAMICS , *MACH number - Abstract
The critical strength of a magnetic field required for the suppression of the Richtmyer-Meshkov instability (RMI) is investigated numerically by using a two-dimensional single-mode analysis. For the cases of magnetohydrodynamic parallel shocks, the RMI can be stabilized as a result of the extraction of vorticity from the interface. A useful formula describing a critical condition for magnetohydrodynamic RMI is introduced and is successfully confirmed by direct numerical simulations. The critical field strength is found to be largely dependent on the Mach number of the incident shock. If the shock is strong enough, even low-β plasmas can be subject to the growth of the RMI. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
20. Enhancement of Ablative Rayleigh-Taylor Instability Growth by Thermal Conduction Suppression in a Magnetic Field.
- Author
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Kazuki Matsuo, Takayoshi Sano, Hideo Nagatomo, Toshihiro Somekawa, King Fai Farley Law, Hiroki Morita, Yasunobu Arikawa, and Shinsuke Fujioka
- Subjects
- *
RAYLEIGH-Taylor instability , *MAGNETIC fields , *THERMAL instability , *LARMOR radius , *THERMAL electrons , *ELECTRON transport - Abstract
Ablative Rayleigh-Taylor instability growth was investigated to elucidate the fundamental physics of thermal conduction suppression in a magnetic field. Experiments found that unstable modulation growth is faster in an external magnetic field. This result was reproduced by a magnetohydrodynamic simulation based on a Braginskii model of electron thermal transport. An external magnetic field reduces the electron thermal conduction across the magnetic field lines because the Larmor radius of the thermal electrons in the field is much shorter than the temperature scale length. Thermal conduction suppression leads to spatially nonuniform pressure and reduced thermal ablative stabilization, which in turn increases the growth of ablative Rayleigh-Taylor instability. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
21. Suppression of the Richtmyer-Meshkov instability due to a density transition layer at the interface.
- Author
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Takayoshi Sano, Kazuki Ishigure, and Cobos-Campos, Francisco
- Subjects
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RICHTMYER-Meshkov instability , *KINETIC energy , *DENSITY , *VELOCITY , *COMPUTER simulation - Abstract
We have investigated the effects of a smooth transition layer at the contact discontinuity on the growth of the Richtmyer-Meshkov instability (RMI) by hydrodynamic numerical simulations, and we derived an empirical condition for the suppression of the instability. The transition layer has little influence on the RMI when the thickness L is narrower than the wavelength of an interface modulation λ. However, if the transition layer becomes broader than λ, the perturbed velocity associated with the RMI is reduced considerably. The suppression condition is interpreted as the cases in which the shock transit time through the transition layer is longer than the sound crossing time of the modulation wavelength. The fluctuation kinetic energy decreases as L-p with p=2.5, which indicates that the growth velocity of the RMI decreases in proportion to L-p/2 by the presence of the transition layer. This feature is found to be quite universal and appeared in a wide range of shock-interface interactions. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
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22. Thermonuclear fusion triggered by collapsing standing whistler waves in magnetized overdense plasmas.
- Author
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Takayoshi Sano, Shinsuke Fujioka, Yoshitaka Mori, Kunioki Mima, and Yasuhiko Sentoku
- Subjects
- *
STANDING waves , *THERMONUCLEAR fusion , *ION acoustic waves , *LASER fusion , *NUCLEAR fusion , *INERTIAL confinement fusion , *ICE nuclei - Abstract
Thermal fusion plasmas initiated by standing whistler waves are investigated numerically by two- and one-dimensional particle-in-cell simulations. When a standing whistler wave collapses due to the wave breaking of ion plasma waves, the energy of the electromagnetic waves transfers directly to the ion kinetic energy. Here we find that ion heating by use of standing whistler waves is operational even in multidimensional simulations of multi-ion species targets, such as deuterium-tritium (DT) ices and solid ammonia borane (H6BN). The energy conversion efficiency to ions becomes as high as 15% of the injected laser energy, which depends significantly on the target thickness and laser pulse duration. The ion temperature could reach a few tens of keV or much higher if appropriate laser-plasma conditions are selected. DT fusion plasmas generated by this method must be useful as efficient neutron sources. Our numerical simulations suggest that the neutron generation efficiency exceeds 109 n/J per steradian, which is beyond the current achievements of the state-of-the-art laser experiments. Standing whistler-wave heating would expand the experimental possibility for an alternative ignition design of magnetically confined laser fusion and also for more difficult fusion reactions, including the aneutronic proton-boron reaction. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
23. Plasma expansion accompanying superthermal electrons in over-picosecond relativistic laser-foil interactions.
- Author
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Natsumi Iwata, Yasuhiko Sentoku, Takayoshi Sano, and Kunioki Mima
- Subjects
RELATIVISTIC electrons ,PLASMA density ,LASER plasmas ,PLASMA dynamics ,PLASMA instabilities ,ULTRASHORT laser pulses - Abstract
We study the plasma expansion dynamics in over-picosecond relativistic laser-foil interactions using one-dimensional particle-in-cell (PIC) simulations. A new expansion mode 'isofield expansion' appears after the well-known isothermal expansion due to the continuous energy input from the laser light to the plasma. The blowout of the heated plasma at the front surface triggers the transition from the isothermal mode to the new mode. In the new expansion mode, electrons and ions expand quasi-neutrally with a constant sheath electric field, and a large scale low density plasma is formed where superthermal electrons are produced efficiently. A two-dimensional PIC simulation confirms the appearance of the isofield expansion mode after the plasma blowout for a large focal spot laser. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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- View/download PDF
24. Ultrafast wave-particle energy transfer in the collapse of standing whistler waves.
- Author
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Takayoshi Sano, Masayasu Hata, Daiki Kawahito, Kunioki Mima, and Yasuhiko Sentoku
- Subjects
- *
STANDING waves , *ENERGY transfer , *PLASMA waves , *FORCE & energy , *SPACE plasmas - Abstract
Efficient energy transfer from electromagnetic waves to ions has been demanded to control laboratory plasmas for various applications and could be useful to understand the nature of space and astrophysical plasmas. However, there exists the severe unsolved problem that most of the wave energy is converted quickly to electrons but not to ions. Here, an energy-to-ion conversion process in overdense plasmas associated with whistler waves is investigated by numerical simulations and a theoretical model. Whistler waves propagating along a magnetic field in space and laboratories often form standing waves by the collision of counter-propagating waves or through the reflection. We find that ions in standing whistler waves acquire a large amount of energy directly from the waves over a short time scale comparable to the wave oscillation period. The thermalized ion temperature increases in proportion to the square of the wave amplitude and becomes much higher than the electron temperature in a wide range of wave-plasma conditions. This efficient ion-heating mechanism applies to various plasma phenomena in space physics and fusion energy sciences. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
25. Broadening of cyclotron resonance conditions in the relativistic interaction of an intense laser with overdense plasmas.
- Author
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Takayoshi Sano, Yuki Tanaka, Natsumi Iwata, Masayasu Hata, Kunioki Mima, Masakatsu Murakami, and Yasuhiko Sentoku
- Subjects
- *
CYCLOTRON resonance , *RELATIVISTIC particles - Abstract
The interaction of dense plasmas with an intense laser under a strong external magnetic field has been investigated. When the cyclotron frequency for the ambient magnetic field is higher than the laser frequency, the laser's electromagnetic field is converted to the whistler mode that propagates along the field line. Because of the nature of the whistler wave, the laser light penetrates into dense plasmas with no cutoff density, and produces superthermal electrons through cyclotron resonance. It is found that the cyclotron resonance absorption occurs effectively under the broadened conditions, or a wider range of the external field, which is caused by the presence of relativistic electrons accelerated by the laser field. The upper limit of the ambient field for the resonance increases in proportion to the square root of the relativistic laser intensity. The propagation of a large-amplitude whistler wave could raise the possibility for plasma heating and particle acceleration deep inside dense plasmas. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
26. SPONTANEOUS FORMATION OF SURFACE MAGNETIC STRUCTURE FROM LARGE-SCALE DYNAMO IN STRONGLY STRATIFIED CONVECTION.
- Author
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Youhei Masada and Takayoshi Sano
- Published
- 2016
- Full Text
- View/download PDF
27. Nonlinear motion of a current-vortex sheet in MHD Richtmyer-Meshkov instability.
- Author
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Chihiro Matsuoka, Katsunobu Nishihara, and Takayoshi Sano
- Published
- 2016
- Full Text
- View/download PDF
28. DEPENDENCE OF THE SATURATION LEVEL OF MAGNETOROTATIONAL INSTABILITY ON GAS PRESSURE AND MAGNETIC PRANDTL NUMBER.
- Author
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Takashi Minoshima, Shigenobu Hirose, and Takayoshi Sano
- Subjects
TURBULENCE ,COMPUTER simulation ,PRANDTL number ,TEARING instability ,PLASMA instabilities - Abstract
A large set of numerical simulations of MHD turbulence induced by the magnetorotational instability is presented. Revisiting the previous survey conducted by Sano et al., we investigate the gas pressure dependence of the saturation level. In ideal MHD simulations, the gas pressure dependence is found to be very sensitive to the choice of numerical scheme. This is because the numerical magnetic Prandtl number varies according to the scheme as well as the pressure, which considerably affects the results. The saturation level is more sensitive to the numerical magnetic Prandtl number than the pressure. In MHD simulations with explicit viscosity and resistivity, the saturation level increases with the physical magnetic Prandtl number, and it is almost independent of the gas pressure when the magnetic Prandtl number is constant. This is indicative of the incompressible turbulence saturated by the secondary tearing instability. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
29. Shock Response of Full Density Nanopolycrystalline Diamond.
- Author
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Kento Katagiri, Norimasa Ozaki, Yuhei Umeda, Tetsuo Irifune, Nobuki Kamimura, Kohei Miyanishi, Takayoshi Sano, Toshimori Sekine, and Ryosuke Kodama
- Subjects
- *
YIELD strength (Engineering) , *DIAMONDS , *CRYSTAL grain boundaries , *DENSITY ,MECHANICAL shock measurement - Abstract
Hugoniot of full-dense nanopolycrystalline diamond (NPD) was investigated up to 1600 GPa. The Hugoniot elastic limit of NPD is 208 (±14) GPa, which is more than twice as high as that of single-crystal diamond. The Hugoniot of NPD is stiffer than that of single-crystal diamond up to 500 GPa, while no significant difference is observed at higher pressures where the elastic precursor is overdriven by a following plastic wave. These findings confirm that the grain boundary strengthening effect recognized in static compression experiments is also effective against high strain-rate dynamic compressions. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
30. Magnetohydrodynamics of laser-produced high-energy-density plasma in a strong external magnetic field.
- Author
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Kazuki Matsuo, Hideo Nagatomo, Zhe Zhang, Nicolai, Philippe, Takayoshi Sano, Shohei Sakata, Sadaoki Kojima, Seung Ho Lee, King Fai Farley Law, Yasunobu Arikawa, Youichi Sakawa, Taichi Morita, Yasuhiro Kuramitsu, Shinsuke Fujioka, and Hiroshi Azechi
- Subjects
- *
MAGNETOHYDRODYNAMICS , *ENERGY density , *MAGNETIC fields - Abstract
Recent progress in the generation in the laboratory of a strong (>100-T) magnetic field enables us to investigate experimentally unexplored magnetohydrodynamics phenomena of a high-energy-density plasma, which an external magnetic field of 200-300 T notably affects due to anisotropic thermal conduction, even when the magnetic field pressure is much lower than the plasma pressure. The external magnetic field reduces electron thermal conduction across the external magnetic field lines because the Larmor radius of the thermal electrons in the external magnetic field is much shorter than the mean free path of the thermal electrons. The velocity of a thin polystyrene foil driven by intense laser beams in the strong external magnetic field is faster than that in the absence of the external magnetic field. Growth of sinusoidal corrugation imposed initially on the laser-driven polystyrene surface is enhanced by the external magnetic field because the plasma pressure distribution becomes nonuniform due to the external magnetic-field structure modulated by the perturbed plasma flow ablated from the corrugated surface. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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