記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/PhysRevE.105.025203

Web of Science

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

At the Earth's low-latitude magnetopause, the Kelvin-Helmholtz instability (KHI), driven by the velocity shear between the magnetosheath and magnetosphere, has been frequently observed during northward interplanetary magnetic field (IMF) periods. However, the signatures of the KHI have been much less frequently observed during southward IMF periods, and how the KHI develops under southward IMF has been less explored. Here, we performed a series of realistic 2D and 3D fully kinetic simulations of a KH wave event observed by the Magnetospheric Multiscale (MMS) mission at the dusk-flank magnetopause during southward IMF on September 23, 2017. The simulations demonstrate that the primary KHI bends the magnetopause current layer and excites the Rayleigh-Taylor instability (RTI), leading to penetration of high-density arms into the magnetospheric side. This arm penetration disturbs the structures of the vortex layer and produces intermittent and irregular variations of the surface waves which significantly reduces the observational probability of the periodic KH waves. The simulations further demonstrate that in the non-linear growth phase of the primary KHI, the lower-hybrid drift instability (LHDI) is induced near the edge of the primary vortices and contributes to an efficient plasma mixing across the magnetopause. The signatures of the large-scale surface waves by the KHI/RTI and the small-scale fluctuations by the LHDI are reasonably consistent with the MMS observations. These results indicate that the multi-scale evolution of the magnetopause KH waves and the resulting plasma transport and mixing as seen in the simulations may occur during southward IMF.

DOI： 10.1063/5.0067391

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

Approximated forms of the third and fourth moments of a velocity distribution function are derived by using a perturbed velocity distribution function around a characteristic spatial scale on the gyroradius derived by Thompson [Rep. Prog. Phys. 24, 363-424 (1961)]. Then, they are evaluated by using a two-dimensional full kinetic Vlasov simulation result of the transverse Kelvin-Helmholtz instability. It is shown that the derived form of the fourth moment is in agreement with the one calculated from the distribution function data of the Vlasov simulation. On the other hand, the derived form of the third moment is quite different from the one (i.e., heat flux tensor) calculated from the distribution function data of the Vlasov simulation. The results suggest that the perturbed velocity distribution function of Thompson needs an improvement.

DOI： 10.1063/1.5139442

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1585/pfr.15.1401002

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review Letters  

A 3D fully kinetic simulation shows that the lower-hybrid drift instability disturbs the front of magnetic reconnection outflow jets and additionally causes energy dissipation. The result is very consistent with a disturbance observed at the dipolarization front (DF) in Earth's magnetotail by the Magnetospheric Multiscale (MMS) mission. A fully kinetic dispersion relation solver, validated by the MMS observations, further predicts that the disturbance of the reconnection jet front could occur over different parameter regimes in space plasmas including Earth's DF and solar flares.

DOI： 10.1103/PhysRevLett.123.235101

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.5129067

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

The stability of contact discontinuities formed by the relaxation of two Maxwellian plasmas with different number densities but the same plasma thermal pressure is studied by means of a one-dimensional electrostatic full Vlasov simulation. Our simulation runs with various combinations of ion-to-electron ratios of the high-density and low-density regions showed that transition layers of density and temperature without jump in the plasma thermal pressure are obtained when the electron temperatures in the high-density and low-density regions are almost equal to each other. However, the stable structure of the contact discontinuity with a sharp transition layer on the Debye scale is not maintained. It is suggested that non-Maxwellian velocity distributions are necessary for the stable structure of contact discontinuities.

DOI： 10.1063/1.5100314

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Computer Physics Communications  

A numerical procedure for integrating the rotation equations of electrically charged particles in magnetic fields with higher accuracy is provided. The proposed n-step rotation schemes have the same accuracy with the standard Boris rotation with 1∕2n−1 time step.

DOI： 10.1016/j.cpc.2018.11.001

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.5079906

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.5053760

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

A simple form of the Boris solver in particle-in-cell (PIC) simulation is proposed. It employs an exact solution of the Lorentz-force part, and it is equivalent to the Boris solver with a gyrophase correction. As a favorable property for stable schemes, this form preserves a volume in the phase space. Numerical tests of the Boris solvers are conducted by test-particle simulations and by PIC simulations. The proposed form provides better accuracy than the popular form, while it only requires few additional computation time.

DOI： 10.1063/1.5051077

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

A current across the magnetic field is formed in various situations in plasma. The relative drift between ions and electrons due to the cross-field current becomes a source of various microscopic instabilities. A fully electromagnetic and kinetic linear dispersion relation for plasma with a drift across magnetic field is derived by assuming a uniform background plasma. The dielectric permittivity tensor for shifted Maxwellian velocity distributions is also presented. Linear dispersion relations obtained by using the new dielectric permittivity tensor were confirmed by comparison with the previous studies and with particle-in-cell simulation results.

DOI： 10.1063/1.5050542

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Geophysical Research: Space Physics  

We examine Magnetospheric Multiscale observations of three ion-scale magnetic flux ropes (diameter ~6–9 ion inertial lengths) in the Earth's magnetotail reconnection diffusion region with a small guide field. During the event, the electron reconnection exhaust reversed direction together with the reversal of normal magnetic field component. After that, the three ion-scale flux ropes were observed near the ion diffusion region, in which flat-top distributions were found at the field-aligned electrons (<2 keV). The axis orientation and motion velocity of the flux ropes are determined by minimum variance analysis of the electric field component along the flux rope axis, using single-spacecraft measurements. Results show that the three flux rope axes form 13°, 55°, and 55° to the guide field direction and are mostly tilted toward the direction of the reconnecting field. These results are also validated by multiple-spacecraft analysis methods. It is found that the tilted angles agree reasonably well with the predicted angles for secondary tearing modes, suggesting that these ion-scale flux ropes are likely generated by secondary tearing instabilities as those recently found in the three-dimensional kinetic simulations of turbulent magnetic reconnection.

DOI： 10.1029/2018JA025775

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Annales Geophysicae  

Large-scale two-dimensional (2-D) full particle-in-cell (PIC) simulations are carried out for studying periodic self-reformation of a supercritical collisionless perpendicular shock with an Alfvén-Mach number MA ∼ 6. Previous self-consistent one-dimensional (1-D) hybrid and full PIC simulations have demonstrated that the periodic reflection of upstream ions at the shock front is responsible for the formation and vanishing of the shock-foot region on a timescale of the local ion cyclotron period, which was defined as the reformation of span styleCombining double low line"" classCombining double low line"text"(quasi-)perpendicular/span> shocks. The present 2-D full PIC simulations with different ion-to-electron mass ratios show that the dynamics at the shock front is strongly modified by large-amplitude ion-scale fluctuations at the shock overshoot, which are known as ripples. In the run with a small mass ratio, the simultaneous enhancement of the shock magnetic field and the reflected ions take place quasi-periodically, which is identified as the reformation. In the runs with large mass ratios, the simultaneous enhancement of the shock magnetic field and the reflected ions occur randomly in time, and the shock magnetic field is enhanced on a timescale much shorter than the ion cyclotron period. These results indicate a coupling between the shock-front ripples and electromagnetic microinstabilities in the foot region in the runs with large mass ratios.

DOI： 10.5194/angeo-36-1047-2018

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.cpc.2018.03.019

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.5031483

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3233/978-1-61499-843-3-178

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1109/HPCC/SmartCity/DSS.2018.00113

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Scopus

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

A two-dimensional, fully kinetic, electromagnetic, particle-in-cell simulation in a magnetized collisionless plasma has been performed, demonstrating the generation of intermittent ion acoustic waves in finite-amplitude whistler-mode turbulence. The self-consistent simulation shows that ion/ion acoustic instability can be driven as a consequence of the nonlinear evolution of whistler-mode turbulence. The instability triggering the generation of ion acoustic waves occurs intermittently in several local regions. We propose that the nonlinear development of the phase-space density that drives kinetic instabilities must be analyzed with greater care if the dissipation of plasma turbulence is to be understood.

DOI： 10.1063/1.4990443

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

The nonlinear evolution of the Rayleigh-Taylor instability (RTI) at a density shear layer transverse to magnetic field in a collisionless plasma is investigated by means of a fully kinetic Vlasov simulation with two spatial and two velocity dimensions. The primary RTI in the MHD regime develops symmetrically in a coordinate axis parallel to gravity as seen in the previous MHD simulations. The primary RTI in the Hall-MHD regime develops asymmetrically in a coordinate axis parallel to gravity. A compressible flow is formed at the secondary density shear layer by the Hall effect, which generates a strong scalar pressure gradient of ions. A Hall electric field due to the diamagnetic current results in the asymmetric flow at the tip of the finger structure. In the primary RTI with the ion gyro kinetic effect, secondary RTI with a wavelength shorter than the wavelength of the primary RTI is generated at the saturation stage of the primary RTI. A seed perturbation for the secondary RTI is excited by another secondary instability due to the coupling between the electron stress tensor and the Hall electric field. The heat flux term plays an important role in the time development of the total pressure. On the other hand, the contribution of the ion stress tensor is small in both the electric current and the total pressure.

DOI： 10.1063/1.4991409

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

The decay of a nonlinear, short-wavelength, and monochromatic electromagnetic whistler wave is investigated by utilizing a two-dimensional (2D) fully relativistic electromagnetic particle-in-cell code. The simulation is performed under a low-beta condition in which the plasma pressure is much lower than the magnetic pressure. It has been shown that the nonlinear (large-amplitude) parent whistler wave decays through the parametric instability in a one-dimensional (1D) system. The present study shows that there is another channel for the decay of the parent whistler wave in 2D, which is much faster than in the timescale of the parametric decay in 1D. The parent whistler wave decays into two sideband daughter whistlers propagating obliquely with respect to the ambient magnetic field with a frequency close to the parent wave and two quasi-perpendicular electromagnetic modes with a frequency close to zero via a 2D decay instability. The two sideband daughter oblique whistlers also enhance a nonlinear longitudinal electrostatic wave via a three-wave interaction as a secondary process.

DOI： 10.1063/1.4982609

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

The nonlinear evolution of the Rayleigh-Taylor instability (RTI) at a density shear layer transverse to magnetic field in collisionless plasma is investigated by means of a fully kinetic Vlasov simulation with two spatial and two velocity dimensions. The primary RTI in the MHD regime develops symmetrically in a coordinate axis parallel to gravity as seen in the previous MHD simulations. Small-scale secondary instabilities are generated due to secondary velocity shear layers formed by the nonlinear development of the primary RTI. The secondary instabilities take place asymmetrically in the coordinate axis parallel to gravity. It is suggested that these secondary instabilities correspond to the electron Kelvin-Helmholtz instability generated by the electron velocity shear, whose development depends on the polarity of the inner product between the magnetic field and the vorticity of the velocity shear layer.

DOI： 10.1063/1.4967859

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/2016GL070215

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

In the present paper, the finite-Larmor-radius (gyro-viscous) term [K. V. Roberts and J. B. Taylor, Phys. Rev. Lett. 8, 197-198 (1962)] is evaluated by using a full kinetic Vlasov simulation result of the Kelvin-Helmholtz instability (KHI). The velocity field and the pressure tensor are calculated from the high-resolution data of the velocity distribution functions obtained by the Vlasov simulation, which are used to approximate the Finite-Larmor-Radius (FLR) term according to Roberts and Taylor [Phys. Rev. Lett. 8, 197-198 (1962)]. The direct comparison between the pressure tensor and the FLR term shows an agreement. It is also shown that the anisotropic pressure gradient enhanced the linear growth of the KHI when the inner product between the vorticity of the primary velocity shear layer and the magnetic field is negative, which is consistent with the previous FLR-magnetohydrodynamic simulation result. This result suggests that it is not sufficient for reproducing the kinetic simulation result by fluid simulations to include the FLR term (or the pressure tensor) only in the equation of motion for fluid.

DOI： 10.1063/1.4952632

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1145/2966884.2966891

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1585/pfr.11.3401031

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Advances in Parallel Computing  

Space plasma is a collisionless, multi-scale, and highly nonlinear medium. Computer simulations with the first-principle kinetic equation are essential for space plasma studies. In the present study, a hyper-dimensional Vlasov (collisionless Boltzmann) simulation code, which is a first-principle method for collisionless space plasma, is parallelized with two-level hybrid MPI and OpenMP and is benchmarked on massively-parallel supercomputer systems. The benchmark result shows that the loop "collapse" directive option of the OpenMP reduces threading overhead of multiple loops. It is also shown that the hybrid parallelism with MPI and OpenMP is useful to reduce the communication time of MPI collective communication subroutines.

DOI： 10.3233/978-1-61499-621-7-265

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

A simple point of view that non-zero Alfvén ratio (residual energy) appears as a consequence of one-fluid modeling of uni-directional Alfvén waves in a solar wind plasma is presented. Since relative speeds among ions are incorporated into the one-fluid model as a pressure anisotropy, the Alfvén ratio can be finite due to the decrease in the phase velocity. It is shown that a proton beam component typically found in the solar wind plasma can contribute to generating non-zero Alfvén ratio observed in the solar wind plasma. Local equilibrium velocity distribution functions of each ion component are also discussed by using maximum entropy principle.

DOI： 10.1063/1.4936798

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

A two-dimensional, fully kinetic, particle-in-cell simulation is used to investigate the nonlinear development of a parallel propagating finite amplitude whistler wave (parent wave) with a wavelength longer than an ion inertial length. The cross field current of the parent wave generates short-scale whistler waves propagating highly oblique directions to the ambient magnetic field through the modified two-stream instability (MTSI) which scatters electrons and ions parallel and perpendicular to the magnetic field, respectively. The parent wave is largely damped during a time comparable to the wave period. The MTSI-driven damping process is proposed as a cause of nonlinear dissipation of kinetic turbulence in the solar wind.

DOI： 10.1063/1.4926523

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Earth, Planets and Space  

The interaction between the solar wind and solar system bodies, such as planets, satellites, and asteroids, is one of the fundamental global-scale phenomena in space plasma physics. In the present study, the electromagnetic environment around a small dielectric body with a weak intrinsic magnetic field is studied by means of a first-principle kinetic plasma simulation, which is a challenging task in space plasma physics as well as high-performance computing. Due to several computational limitations, five-dimensional full electromagnetic Vlasov simulations with two configuration space and three velocity space coordinates are performed with two different spatial resolutions. The Debye-scale charge separation is not solved correctly in the simulation run with a low spatial resolution, while all the physical processes in collisionless plasma are included in the simulation run with a high spatial resolution. The direction comparison of electromagnetic fields between the two runs shows that there is small difference in the structure of magnetic field lines. On the other hand, small-scale fine structures of electrostatic fields are enhanced by the electric charge separation and the charge accumulation on the surface of the body in the high-resolution run, while these structures are absent in the low-resolution runs. These results are consistent with the conventional understanding of plasma physics that the structure and dynamics of global magnetic fields, which are generally described by the magneto-hydro-dynamics (MHD) equations, are not affected by electron-scale microphysics.

DOI： 10.1186/s40623-015-0216-0

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1109/CANDAR.2015.25

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

Relativistic electron acceleration through dissipation of a nonlinear, short-wavelength, and monochromatic electromagnetic whistler wave in low-beta plasma is investigated by utilizing a one-dimensional fully relativistic electromagnetic particle-in-cell code. The nonlinear (large-amplitude) parent whistler wave decays through the parametric instability which enhances electrostatic ion acoustic waves and electromagnetic whistler waves. These waves satisfy the condition of three-wave coupling. Through the decay instability, the energy of electron bulk velocity supporting the parent wave is converted to the thermal energy perpendicular to the background magnetic field. Increase of the perpendicular temperature triggers the electron temperature anisotropy instability which generates broadband whistler waves and heats electrons in the parallel direction. The broadband whistler waves are inverse-cascaded during the relaxation of the electron temperature anisotropy. In lower-beta conditions, electrons with a pitch angle of about 90° are successively accelerated by inverse-cascaded whistler waves, and selected electrons are accelerated to over a Lorentz factor of 10. The result implies that the nonlinear dissipation of a finite-amplitude and short-wavelength whistler wave plays an important role in producing relativistic nonthermal electrons over a few MeV especially at lower beta plasmas.

DOI： 10.1088/0004-637X/794/1/63

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Plasma Physics and Controlled Fusion  

The nonlinear evolution of the Kelvin-Helmholtz (KH) instability at a transverse velocity shear layer in an inhomogeneous space plasma is investigated by means of a four-dimensional (two spatial and two velocity dimensions) electromagnetic Vlasov simulation. When the rotation direction of the primary KH vortex and the direction of ion gyro motion are the same (i.e., the inner product between the vorticity of the primary velocity shear and the magnetic field vector is negative) there exists a strong ion cyclotron damping. In this case, spatial inhomogeneity inside the primary KH vortex is smoothed and the secondary Rayleigh-Taylor/KH instabilities are suppressed. It is also found that another secondary instability on the electron inertial scale is simultaneously generated at secondary shear layers for both cases, but at different locations. The small-scale secondary instability takes place only when the inner product between the vorticity of the secondary shear layer and the magnetic field vector is positive, suggesting the damping of small-scale processes by ion gyro motion. These results indicate that secondary instabilities occurring in the nonlinear stage of the primary KHI show different evolutions depending on the sign of the inner product between the magnetic field and the vorticity of the velocity shear layer. © 2014 IOP Publishing Ltd.

DOI： 10.1088/0741-3335/56/7/075006

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Planetary and Space Science  

The interaction between a plasma flow and a small dielectric body with a weak intrinsic global magnetic field is studied by means of a five-dimensional full electromagnetic Vlasov simulation with two configuration spaces and three velocity spaces. In the present study, entry processes of ions into the nightside wake tail are examined. The simulation result shows that the bow shock and the magnetopause are formed on the dayside. However, most of solar-wind ions are reflected at the dayside magnetopause and are picked up by the interplanetary magnetic field. Then, a small part of the reflected ions are taken into the deep wake tail near the body by the E×B cycloid motion. © 2014 Elsevier Ltd.

DOI： 10.1016/j.pss.2014.02.002

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

The structure of the diffusion regions in antiparallel magnetic reconnection is investigated by means of a theory and a Vlasov simulation. The magnetic diffusion is considered as relaxation to the frozen-in state, which depends on a reference velocity field. A field-aligned component of the frozen-in condition is proposed to evaluate a diffusion-like process. Diffusion signatures with respect to ion and electron bulk flows indicate the ion and electron diffusion regions near the reconnection site. The electron diffusion region resembles the energy dissipation region. These results are favorable to a previous expectation that an electron-scale dissipation region is surrounded by an ion-scale Hall-physics region. © 2014 AIP Publishing LLC.

DOI： 10.1063/1.4869717

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

Large-scale two-dimensional (2D) full particle-in-cell (PIC) simulations are carried out for studying the relationship between the dynamics of a perpendicular shock and microinstabilities generated at the shock foot. The structure and dynamics of collisionless shocks are generally determined by Alfven Mach number and plasma beta, while microinstabilities at the shock foot are controlled by the ratio of the upstream bulk velocity to the electron thermal velocity and the ratio of the plasma-to-cyclotron frequency. With a fixed Alfven Mach number and plasma beta, the ratio of the upstream bulk velocity to the electron thermal velocity is given as a function of the ion-to-electron mass ratio. The present 2D full PIC simulations with a relatively low Alfven Mach number (MA ∼ 6) show that the modified two-stream instability is dominant with higher ion-to-electron mass ratios. It is also confirmed that waves propagating downstream are more enhanced at the shock foot near the shock ramp as the mass ratio becomes higher. The result suggests that these waves play a role in the modification of the dynamics of collisionless shocks through the interaction with shock front ripples. © 2014 AIP Publishing LLC.

DOI： 10.1063/1.4863836

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Scopus

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nonlinear Processes in Geophysics  

The numerical simulation of the nonlinear evolution of the parallel propagating Alfvén waves in a radially expanding plasma is performed by using a kinetic-fluid model (the Vlasov-MHD model). In our study, both the nonlinear evolution of the Alfvén waves and the radial evolution of the velocity distribution function (VDF) are treated simultaneously. On the other hand, important ion kinetic effects such as ion cyclotron damping and instabilities driven by the non-equilibrium ion velocity distributions are not included in the present model. The results indicate that the steepened Alfvén wave packets outwardly accelerate ions, which can be observed as the beam components in the interplanetary space. The energy of imposed Alfvén waves is converted into the longitudinal fluctuations by the nonlinear steepening and the nonlinear Landau damping. The wave shoaling due to the inhomogeneity of the phase velocity is also observed. © Author(s) 2014.

DOI： 10.5194/npg-21-339-2014

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Advances in Parallel Computing  

Magnetohydrodynamic (MHD) simulations are often applied to study the global dynamics and configuration of the planetary magnetosphere. The computational performance of an MHD code is evaluated on a massive parallel scalar type supercomputer system with one PFlops ideal performance. We have made the performance tuning of our three-dimensional MHD code for the planetary magnetosphere on the FX10 which has 76,800 cores, distributed on 4,800 SPARC64 IXfx nodes. For the parallelization of the MHD code, we use four different methods, i.e. one-dimensional, two-dimensional, three-dimensional regular domain decomposition methods and a cache-hit type of three-dimensional domain decomposition method. We found that the cache-hit type of three-dimensional decomposition of the MHD model is suitable for the FX10 system. We also found the pack/unpack operation for the inter-node communications decreases the execution efficiency by 2 %. After asynchronous communication is introduced and the pack/unpack operation is overlapped, we achieved a computing performance of 230 TFlops and an efficiency of almost 20 % for the MHD code. © 2014 The authors and IOS Press.

DOI： 10.3233/978-1-61499-381-0-387

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.4816809

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J-GLOBAL

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Physics: Conference Series  

Space plasma is a collisionless, multi-scale, and highly nonlinear medium. There are various types of self-consistent computer simulations that treat space plasma according to various approximations. We develop numerical schemes for solving the Vlasov (collisionless Boltzmann) equation, which is the first-principle kinetic equation for collisionless plasma. The weak-scaling benchmark test shows that our parallel Vlasov code achieves a high performance and a high scalability. Currently, we use more than 1000 cores for parallel computations and apply the present parallel Vlasov code to various cross-scale processes in space plasma, such as a global simulation on the interaction between solar/stellar wind and magnetospheres of astronomical objects.

DOI： 10.1088/1742-6596/454/1/012005

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：International Journal of High Performance Computing Applications  

The computational performance of magnetohydrodynamic (MHD) code is evaluated on two typical scalar-type supercomputer systems. We have carried out performance tuning of a three-dimensional MHD code for space plasma simulations on the HA8000 (with 8192 cores) and SR16000/L2 (with 1344 cores) supercomputer systems. For parallelization of the MHD code, we use four different methods, that is, regular one-dimensional, two-dimensional and three-dimensional domain decomposition methods and a cache-hit type of three-dimensional domain decomposition method. We found that the regular three-dimensional decomposition of the MHD model is suitable for the HA8000 system, and the cache-hit type of three-dimensional decomposition is suitable for SR16000/L2 systems. As a result of these runs, we achieved a performance efficiency of almost 15% on the HA8000 and 20% on the SR16000/L2 for MHD code. © The Author(s) 2012.

DOI： 10.1177/1094342011434813

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

A positive slope in a velocity distribution function perpendicular to the ambient magnetic field, such as due to a loss cone or ring velocity distribution, can become a free energy source for the excitation of various plasma waves. Since there exists no analytic expression for integrals of Maxwellian ring velocity distribution functions, their linear properties have previously been studied using several approximations or modeled distributions. In this paper, a numerical method for analyzing the linear dispersion relation for Maxwellian ring-beam velocity distributions is developed. The obtained linear properties are confirmed by direct comparison with full particle simulation results. © 2012 American Institute of Physics.

DOI： 10.1063/1.4736848

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Geophysical Research: Space Physics  

Electrostatic solitary structures have been observed in the Earth's magnetosheath by the Cluster spacecraft. Recent theoretical work has suggested that these solitary structures are modeled by electron acoustic solitary waves existing in a four-component plasma system consisting of core electrons, two counter-streaming electron beams, and one species of background ions. In this paper, the excitation of electron acoustic waves and the formation of solitary structures are studied by means of a one-dimensional electrostatic Vlasov simulation. The present result first shows that either electron acoustic solitary waves with negative potential or electron phase-space holes with positive potential are excited in four-component plasma systems. However, these electrostatic solitary structures have longer duration times and higher wave amplitudes than the solitary structures observed in the magnetosheath. The result indicates that a high-speed and small free energy source may be needed as a fifth component. An additional simulation of a five-component plasma consisting of a stable four-component plasma and a weak electron beam shows the generation of small and fast electron phase-space holes by the bump-on-tail instability. The physical properties of the small and fast electron phase-space holes are very similar to those obtained by the previous theoretical analysis. The amplitude and duration time of solitary structures in the simulation are also in agreement with the Cluster observation.

DOI： 10.1029/2011JA017181

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE Transactions on Plasma Science  

Numerical schemes for solving the Vlasov-Maxwell system equations are studied. For studies of cross-scale coupling between fluid-scale dynamics and particle-scale kinetics in collisionless plasma, both highly scalable kinetic code and huge supercomputer are essential. In the present study, a new parallel Vlasov-Maxwell solver is developed by adopting a stable but less dissipative scheme for time integration of conservation laws. The new code has successfully achieved a high scalability on massively parallel supercomputers with multicore scalar processors. The new code has been applied to 2P3V (two dimensions for position and three dimensions for velocity) problems of cross-scale plasma processes such as magnetic reconnection, Kelvin-Helmholtz instability, and interaction between the solar wind and an asteroid. © 1973-2012 IEEE.

DOI： 10.1109/TPS.2012.2188141

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.cpc.2012.01.011

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J-GLOBAL

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

A full particle simulation study is carried out for studying microinstabilities generated at the shock front of perpendicular collisionless shocks. The structure and dynamics of shock waves are determined by Alfvén Mach number and plasma beta, while microinstabilities are controlled by the ratio of the upstream bulk velocity to the electron thermal velocity and the plasma-to-cyclotron frequency. Thus, growth rates of microinstabilities are changed by the ion-to-electron mass ratio, even with the same Mach number and plasma beta. The present two-dimensional simulations show that the electron cyclotron drift instability is dominant for a lower mass ratio, and electrostatic electron cyclotron harmonic waves are excited. For a higher mass ratio, the modified two-stream instability is dominant and oblique electromagnetic whistler waves are excited, which can affect the structure and dynamics of collisionless shocks by modifying shock magnetic fields. © 2012 American Institute of Physics.

DOI： 10.1063/1.3703319

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Geophysical Research: Space Physics  

A full particle simulation study is carried out for studying microinstabilities generated in self-consistently excited perpendicular collisionless shocks. The present two-dimensional simulation with a high ion-to-electron mass ratio shows that the modified two-stream instability can be generated by the interaction of incoming and reflected ions with electromagnetic whistler mode waves propagating in the direction quasi-perpendicular to the ambient magnetic field. Properties of the excited whistler mode waves are consistent with the linear dispersion analysis based on the simulated velocity distribution functions. It is also found that the excited waves have an electron-scale wavelength in the shock-normal direction and an ion-scale wavelength in the shock-tangential direction, suggesting that the electron-scale microturbulences and the ion-scale shock structures are coupled with each other through the modified two-stream instability. Copyright 2012 by the American Geophysical Union.

DOI： 10.1029/2011JA017182

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Earth, Planets and Space  

The global structure of wake fields behind an unmagnetized object in the solar wind is studied by means of a 2.5-dimensional full electromagnetic Vlasov simulation. The interaction of a plasma flow with an unmagnetized object is quite different from that with a magnetized object such as the Earth. Due to the absence of the global magnetic field, the unmagnetized object absorbs plasma particles which reach the surface, generating a plasma cavity called a wake on the anti-solar side of the object. The interaction between the solar wind with an out-of-plane interplanetary magnetic field and an unmagnetized object of ion-gyro scale is examined to study the effect of the ion cyclotron motion on the structure of wake fields. It is shown that the wake boundary layer is broadened when the inner product of the electric force and the density gradient of the wake boundary layer is negative. On the other hand, a steep wake boundary layer is formed with a negative inner product. The result suggests that the structures of wake fields become asymmetric due to the in-plane E cross B drift motion of ions. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).

DOI： 10.5047/eps.2011.05.035

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

Shock drift acceleration is one of the important mechanisms for electron acceleration associated with magnetic mirror reflection along the magnetic field in a quasi-perpendicular collisionless shock. We study the influence of a rippled shock surface in the in-plane magnetic field on the magnetic mirror reflection of electrons. Simulation results show that the number of reflected electrons reduces after generation of the rippled shock surface. Electric and magnetic wavenumber spectra of the generated fluctuations in the shock transition region indicate the existence of kinetic Alfvén turbulence. The kinetic Alfvén turbulence decreases the electron pitch angle by parallel scattering, which reduces the magnetic mirror force acting on the electrons. These results suggest that the shock-generated kinetic Alfvén turbulence suppresses the magnetic mirror reflection of electrons during the shock drift acceleration. © 2011. The American Astronomical Society. All rights reserved.

DOI： 10.1088/0004-637X/736/1/35

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.pss.2011.02.017

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.pss.2010.01.007

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.3574359

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2010JA015682

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J-GLOBAL

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Plasma Physics and Controlled Fusion  

In this paper, spectra in the nonlinear phases of the Buneman instability are described by instantaneous linear dispersion theory. One-dimensional Vlasov simulation of the Buneman instability shows that nonlinear development is characterized by particle trapping in large-amplitude waves. Trapped particles form counter-streaming beam distribution function in velocity space. In addition to the low-frequency Buneman mode, the simulation also shows excitations of high-frequency electron plasma waves as well as wave modes propagating in the direction opposite to the original electron beam. The actual physics of the wave dynamics is very complicated to analyze. However, by employing linear dispersion theory on the basis of instantaneous electron distributions it is possible to relate the generation of waves to the particle distribution. Specifically, it is shown that excitations of various waves are intimately related to the counter-streaming electron beam distribution. The present approach can be a useful diagnostic tool based upon which an intuitive understanding of the complicated nonlinear physics can be attained. © 2011 IOP Publishing Ltd Printed in the UK & the USA.

DOI： 10.1088/0741-3335/53/2/025010

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.3551510

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.3517103

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2010JA015458

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1109/TPS.2010.2056704

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1109/TPS.2010.2057451

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1109/TPS.2010.2055162

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.3422547

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.3403345

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.3425872

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2009JA014643

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2008JA013562

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J-GLOBAL

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

A full particle simulation study is carried out on the electron acceleration at a collisionless, relatively low Alfven Mach number (M_A = 5), perpendicular shock. Recent self-consistent hybrid shock simulations have demonstrated that the shock front of perpendicular shocks has a dynamic rippled character along the shock surface of low Mach number perpendicular shocks. In this paper, the effect of the rippling of perpendicular shocks on the electron acceleration is examined by means of large-scale (ion-scale) two-dimensional full particle simulations. It has been shown that a large-amplitude electric field is excited at the shock front in association with the ion-scale rippling, and that reflected ions are accelerated upstream at a localized region where the shock-normal electric field of the rippled structure is polarized upstream. The current-driven instability caused by the highly accelerated reflected ions has a high growth rate of up to large-amplitude electrostatic waves. Energetic electrons are then generated by the large-amplitude electrostatic waves via electron surfing acceleration at the leading edge of the shock-transition region. The present result suggests that the electron surfing acceleration is also a common feature at low Mach number perpendicular collisionless shocks.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A detailed procedure of full-electromagnetic Vlasov simulation technique is presented. Our new unsplitting conservative scheme exactly satisfies the continuity equation for charge. The implicit Finite Difference Time Domain method is also adopted for computation of electromagnetic fields, which is not restricted by the CFL condition for light. The Geospace Environment Modeling magnetic reconnection challenge problem is adopted as a benchmark test. The characteristics of the present Vlasov code are studied by varying the resolution in configuration space.

DOI： 10.1016/j.cpc.2008.11.001

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Earth, Planets and Space  

We present a magnetohydrodynamic (MHD) simulation technique with a new non-oscillatory and conservative interpolation scheme. Several high-resolution and stable numerical schemes have recently been proposed for solving the MHD equations. To apply the CIP scheme to the hydrodynamic equations, we need to add a certain diffusion term to suppress numerical oscillations at discontinuities. Although the TVD schemes can automatically avoid numerical oscillations, they are not appropriate for profiles with a local maximum or minimum, such as waves. To deal with the above problems, we implement a new non-oscillatory and conservative interpolation scheme in MHD simulations. Several numerical tests are carried out in order to compare our scheme with other recent high-resolution schemes. The numerical tests suggest that the present scheme can follow long-term evolution of both Alfvén waves and compressive shocks. The present scheme has been used for a numerical modeling of Alfvén waves in the solar wind, in which sinusoidal Alfvén waves decay into compressive sound waves that steepen into shocks.rigaku corporation, japan. Copyright © the society of geomagnetism and earth.

DOI： 10.1186/BF03353200

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.2965494

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Web of Science

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

Nonlinear evolution of the electron two-stream instability in a current-carrying plasma is examined by using a two-dimensional electromagnetic particle-in-cell simulation. Formation of electron phase-space holes is observed as an early nonlinear consequence of electron-beam-plasma interactions. Lower-hybrid waves, electrostatic, and electromagnetic whistler mode waves are also excited by different mechanisms during the ensuing nonlinear wave-particle interactions. It is shown by the present computer simulation with a large simulation domain and a long simulation time that these low-frequency waves can disturb the electrostatic equilibrium of electron phase-space holes, suggesting that the lifetime of electron phase-space holes sometimes becomes shorter in a current-carrying plasma. © 2008 American Institute of Physics.

DOI： 10.1063/1.2937818

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.asr.2007.04.018

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J-GLOBAL

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2007JA012513

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.2779282

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2006JA012124

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.5194/npg-14-671-2007

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Web of Science

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1017/S0022377806005228

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2006JA011762

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J-GLOBAL

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physics of Plasmas  

Mechanisms for the generation of Langmuir wave packets are studied by performing a one-dimensional electrostatic Vlasov simulation. The present simulation of a weak-electron-beam instability without ion dynamics suggests two new processes for the amplitude modulation of Langmuir waves. The beam instability excites Langmuir modes over a wide wave number range, but the saturation of the most unstable Langmuir mode "filters" the growth of sideband modes. Specific upper and lower sideband modes linearly grow to a high saturation level. Then the primary Langmuir mode is amplified and strongly modulated through interaction with the sideband modes. © 2006 American Institute of Physics.

DOI： 10.1063/1.2348088

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1029/2006GL025708

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J-GLOBAL

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Earth, Planets and Space  

The full kinetic dynamics of a perpendicular collisionless shock is studied by means of a one-dimensional electromagnetic full particle simulation. The present simulation domain is taken in the shock rest frame in contrast to the previous full particle simulations of shocks. Preliminary results show that the downstream state falls into a unique cyclic reformation state for a given set of upstream parameters through the self-consistent kinetic processes. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.

DOI： 10.1186/BF03352617

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

開催年月日： 2013年1月

記述言語：英語   会議種別：口頭発表（一般）  

DOI： 10.1007/978-3-642-45037-2_60

Scopus

開催年月日： 2012年10月

記述言語：英語   会議種別：口頭発表（一般）  

DOI： 10.1007/978-3-642-33078-0_17

Scopus

開催年月日： 2011年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2011年11月

記述言語：英語   会議種別：口頭発表（一般）  

DOI： 10.1109/URSIGASS.2011.6051058

Scopus

開催年月日： 2011年11月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Seattle  

開催年月日： 2011年8月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Istanbul Lutfi Kirdar Convention & Exhibition Centre  

開催年月日： 2011年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Banff Conference Centre  

開催年月日： 2010年11月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：New Orleans  

開催年月日： 2010年10月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2010年9月

記述言語：英語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2010年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2010年6月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2009年9月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2009年8月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2009年8月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催年月日： 2009年7月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催年月日： 2009年3月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2009年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2008年11月

記述言語：英語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2008年10月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2008年3月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2007年12月

記述言語：日本語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2007年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2007年2月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催年月日： 2006年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2006年10月

記述言語：英語   会議種別：口頭発表（招待・特別）  

国名：日本国  

開催年月日： 2005年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2004年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2004年7月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催年月日： 2003年7月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2002年8月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2002年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催年月日： 2001年9月

記述言語：英語   会議種別：口頭発表（招待・特別）  

開催年月日： 2001年8月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する

数値解析ソフトScilabの使用法を習得し、人工衛星が観測したデータを解析する