PEM26-P01

Room:Convention Hall

Time:May 24 18:15-19:30

Investigation of Energetic Particle Hybrid Simulation ModelAMANO, Takanobu1∗
1

University of Tokyo

Energetic particle populations coexisting with the thermal gas are commonly found in space plasma environments. Although
the number density of the energetic particles is usually much lower than the thermal population, the energy density is often substantial. Typical examples include the thermal gas and galactic cosmic rays in the interstellar medium, a cold plasma originatingfrom the ionosphere and the energetic ring-current population in the inner magnetosphere.
The typical scale sizes such as the Larmor radius between the two population are vastly different, making it important to take
into account kinetic effect of energetic particles even for the macroscopic dynamics in which the fluid approximation for thethermal population is adequate. The difference in scale size makes it impractical to deal with both the components in a fully
kinetic manner.
Here we propose a method that deals with only the energetic particles as a kinetic population whereas the fluid approximation
is used for the thermal gas. We will demonstrate that this may be achieved as a natural extension of our recently developed quasineutral two-fluid plasma simulation code. Several preliminary simulation results will be discussed to investigate the validity ofthe model.
Keywords: numerical simulation, plasma, cosmic rays

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PEM26-P02

Room:Convention HallTime:May 24 18:15-19:30

Nonlinear evolution of MRI studied by an MHD code with the compact difference schemeand the LAD method
HIRAI, Kenichiro1∗ ; KATOH, Yuto1 ; TERADA, Naoki1 ; KAWAI, Soshi2
1

Department of Geophysics, Graduate School of Science, Tohoku University, 2 Department of Aerospace Engineering, Graduate
School of Engineering, Tohoku University
The magnetorotational instability (MRI) is one of the most important phenomena in the accretion disk. Turbulence generatedby MRI causes the turbulent viscosity in the disk and is a strong candidate of the driver of mass accretion. Recent study suggested
that the turbulence induced by MRI also plays an important role in the planetesimal formation in the protoplanetary disk. In theplanetesimal formation process, both the ionized gas and dusts coexist in the disk and the motion of dusts is strongly affected by
the motion of gas through collisional and/or frictional effects. Kato et al. (2010;2012) showed the possibility that meter-sized
dusts are gathered locally due to the modification of the disk gas distribution through the evolution of MRI and that situations
favored for the planetesimal formation are created in the localized region. In addition to the effect pointed out by this simulation,
we should take into account effects through the Kelvin-Helmholtz instability (Sekiya, 1998; Barranco, 2009) and the streaminginstability (Youdin & Goodman, 2005) generated by the dust-gas interaction as well as the time evolution of the global discstructure (Suzuki et al., 2010). In order to carry out the MHD simulation considering these effects, we need to develop thescheme that can accurately resolve both short wavelength waves in turbulence and discontinuity appeared in the evolution ofinstabilities.
In the present study, we develop an MHD simulation code using an 8th-order compact difference scheme with the local
artificial diffusivity (LAD) method (Kawai, 2013). The compact difference scheme proposed by Lele (1992) enables us to solve
turbulent flow accurately up to the wavenumber range corresponding to a few grid points. The LAD method for MHD simulation
proposed by Kawai (2013) enables us to reduce unphysical oscillations generated in central difference type scheme like thecompact difference scheme. We have also applied parallelization by MPI using the pipeline algorithm to the code in order toincrease the box size with keeping the high spatial resolution. By using the pipeline algorithm, we have applied the domain
decomposition to the code with maintaining the accuracy of the compact difference scheme. We carry out a series of standard
test problems for MHD simulations and clarify pros and cons of the developed MHD code for the study of MRI. By conducting
spatially 2-dimensional test problems, we find that the maximum value of the numerical error appeared in the computation of thedivergence of the magnetic field is the order of 10−12 , which is approximately consistent with the results of Kawai (2013).
We then carry out the 3-dimensional MHD simulation of MRI by the developed code. In order to realize the differentialrotation, we use the shearing box boundary condition (Hawley et al., 1995) and the 9-wave method (Dedner et al, 2010) so as
to suppress the divergence error caused by the interpolation in the shearing box boundary. We initially set the uniform verticalmagnetic field and assume the perturbation in the three-components of the velocity vector whose amplitude is 1% of the soundspeed. Our developed simulation code can solve the linear growth and nonlinear evolution of MRI. Our newly developed code
enables us to solve the MRI driven turbulence accurately, which is important in solving not only a wide range of the evolution ofthe disk but also the fine structure of the saturation and nonlinear evolution mechanism of MRI. We show the characteristics ofthe developed code and study results of the 3-dimensional MHD simulation of the nonlinear evolution of MRI.

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PEM26-P03

Room:Convention Hall

Time:May 24 18:15-19:30

Yin-Yang Dynamo Simulation with in-situ visualization Using ParaView/Catalyst
SUGA, Arata1∗ ; KAGEYAMA, Akira1
1

Graduate School of System Informatics, Kobe University

In accordance with the development of high performance computers, the data size of large scale simulations is exponentiallygrowing. The post process visualization, which is currently the major approach to the data analysis in computer simulation
research, might be in deadlock in the near future. The in-situ visualization method is attracting attention as a solution to thisproblem. We have recently realized an in-situ visualization of a magnetohydrodynamic (MHD) dynamo simulation using theYin-Yang grid. We have used ParaView and Catalyst for visualization engine and its interface to the MHD simulation code forthe in-situ visualization.
Keywords: Visualization, in-situ visualization, Yin-Yang grid

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PEM26-P04

Room:Convention Hall

Time:May 24 18:15-19:30

PIC simulations on magnetic perturbation around the Solar Probe Plus spacecraft
FUNAKI, Yuji1∗ ; KIKURA, Keisuke1 ; MIYAKE, Yohei1 ; USUI, Hideyuki1
1Graduate School of System Informatics, Kobe University

For future space exploration, it is necessary to predict the nature of spacecraft-plasma interactions in extreme plasma environmental conditions. As one of such activities, we study on the physics of spacecraft-plasma interactions in the near-Sunenvironment. The spacecraft environment immersed in the solar corona is characterized by the small Debye length due to its
high density (7000 /cc) and a large photo-/secondary electron emission current emitted from the spacecraft surfaces, which leadto much different nature of spacecraft-plasma interactions from that in the near-Earth environment. Consequently, the spacecraft
charges negatively near the Sun unlike usual photo-emitting spacecraft in the near-Earth environment. In the present study, wereproduce the plasma environment around the Solar Probe Plus satellite planned by NASA by means of numerical simulations
based on the Particle-in-cell method. We report recent research progress on near-spacecraft magnetic perturbations, which isgenerated by a complex current closure around the spacecraft.
Keywords: spacecraft-plasma interaction, solar coronal plasma, spacecraft charging, photoelectron emission, magnetic perturbation, PIC simulation

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PEM26-P05

Room:Convention Hall

Time:May 24 18:15-19:30

Electron temperature anisotropy during compression of current sheets thicker than the ion
skin depth
SHIMIZU, Kenya1∗ ; FUJIMOTO, Masaki2 ; SHINOHARA, Iku2
1EPS, SOS, Univ. of Tokyo, 2 JAXA/ISAS

Collisionless magnetic reconnection drives explosive release of magnetic energy to kinetic and thermal energy of plasmas
in space plasma phenomena, such as solar flares and convection of plasmas and magnetic fields in the Earth’s magnetosphere.
Satellite observations in the Earth’s magnetotail have shown that an initial current sheet ten times thicker than the local ion skindepth gets as thin as the ion skin depth, when magnetic reconnection is triggered in the sheet. According to the linear analysisof the tearing instability, the thicker the thickness of current sheets is, the exponentially lower the growth rate is, while thestronger the anisotropy of plasmas is, the higher the growth rate is. Current sheets can be thin due to the Dawn-Dusk electric field
associated with the convection of magnetic fields in the Earth’s magnetosphere and effects of the lower-hybrid drift instability.
However, it is not fully understood how magnetic reconnection is triggered in a current sheet much thicker than the ion skindepth.
In this study, we perform the current sheet thinning by using the one-dimensional PIC simulation imposed the Dawn-Dusk
electric field at boundaries with various initial parameters. We investigate the dependence on the initial parameters of the strengthand the distribution of the anisotropy and of the compression level of current sheets. The results show that (1) the distribution of
the anisotropy changes with the initial thickness of current sheets, (2) the strength of the anisotropy at the center of current sheets
is explained by the adiabatic heating perpendicular to magnetic fields regardless of the initial parameters, (3) the compression
level of current sheets normalized by the local ion skin depth is much lower than the ratio of the terminal strength of the lobe
magnetic field to the initial strength of that. These results can be useful to understand processes of the current sheet thinning andthe trigger of magnetic reconnection in multidimensional simulations including the tearing instability and/or the lower-hybrid
drift instability.

Keywords: magnetic reconnection

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PEM26-P06

Room:Convention Hall

Time:May 24 18:15-19:30

Validity of gyro-averaging method for oblique whistler-mode wave particle interaction
HSIEH, Yikai1∗ ; OMURA, Yoshiharu1
1Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan.

We perform test particle simulations of energetic electrons interacting with oblique whistler-mode waves in the Earth’s magnetic field. We first solve exact equations of motion of test electrons under the electric and magnetic fields of obliquely propagating coherent wave with right-hand polarization. In this test, the energetic electrons undergo multiple cyclotron resonances. We
also apply gyro-averaging method by treating electron motion as its guiding center motion to simplify the complicated cyclotron
motion [1,2]. The result shows that the gyro-averaging motion is successfully consistent with the direct motion of the electron.
Applying this result we can just use the guiding center motion of electrons to represent the completed motion of electrons. Therefore, these method can be utilized in the particle simulations of oblique propagation waves to reduce the relativistic equations ofmotion and minimize the computation resources, which makes simulations of multiple particles more feasible.
References[1] Bell (1984), The nonlinear gyroresonance interaction between energetic electrons and coherent VLF waves propagating at
an arbitrary angle with respect to the Earth’s magnetic field. J. geophys. Res. 89, 905.
[2] Nunn and Omura, A computational and theoretical investigation of nonlinear wave particle interactions in oblique whistlers,
Submitted to J. Geophys. Res. .
Keywords: whistler-mode wave, oblique propagattion

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PEM26-P07

Room:Convention Hall

Time:May 24 18:15-19:30

Effects of the alpha-proton drift velocity on alpha firehose instabilities in the solar wind
JUNGJOON, Seough1∗ ; NARIYUKI, Yasuhiro2 ; YOON, Peter H.3
1Faculty of Human Development, University of Toyama / JSPS Postdoctor Fellow, 2 Faculty of Human Development, Universityof Toyama, 3 IPST, University of Maryland / School of Space Research, Kyung Hee University
In situ measurements have shown that the less-abundant alpha particles are characterized by temperature anisotropy which
could drive the anisotropy-driven kinetic instabilities in the solar wind. In the collisionless limit, the differential alpha-proton
flow velocity usually has finite value of the order of the local Alfven velocity. The presence of such differential flow may affectthe properties of dispersion relations for anisotropy-driven instabilities. By making use of linear Vlasov theory, the present study
investigates the effects of the alpha-proton drift velocity on firehose instabilities driven by parallel temperature anisotropy of alphaparticles. It is found that for parallel firehose mode the dispersion properties are asymmetric in that the maximum growth rateis larger for forward propagating mode than for backward propagating one in the proton rest frame. For both parallel (forward
propagating mode) and oblique firehose instabilities overall growth rates increase as the alpha-proton drift velocity increases.
Consequently, the firehose instability thresholds are distinctly influenced by the presence of the alpha-proton drift velocity.
Keywords: firehose instability, solar wind ions, the alpha-proton drift

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PEM26-P08

Room:Convention Hall

Time:May 24 18:15-19:30

Vlasov simulation of the Rayleigh-Taylor instability
WADA, Yasutaka1∗ ; UMEDA, Takayuki1 ; UENO, Satoshi1 ; MACHIDA, Shinobu1
1

Solar-Terrestrial Environment Laboratory

The Rayleigh-Taylor instability (RTI) develops at an interface between two fluids with different densities when an external
force is applied from a heavy fluid to a light fluid. In the previous studies of ideal MHD simulations, the RTI develops symmetrically in the horizontal axis. On the other hand, previous hall-MHD and Finite-Larmor-Radius (FLR)-MHD simulations
have shown that the RTI develops asymmetrically in the horizontal axis. In this study, we perform four-dimensional Vlasov
simulations of the RTI with two spatial dimensions and three velocity dimensions. We vary the ratio of the ion inertial length
and/or the ion gyroradius to the spatial scale of the density gradient layer, and discuss the effect of the non-MHD effects on thegrowth of the RTI.
Keywords: Rayleigh-Taylor instability, Vlasov simulation, space plasma

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PEM26-P09

Room:Convention Hall

Time:May 24 18:15-19:30

3-dimentional electromagnetic particle simulations about the low frequency componentof Broadband Electrostatic NoiseMIYAKE, Taketoshi1∗ ; NAGAYASU, Sho1 ; OKADA, Masaki2 ; OMURA, Yoshiharu3 ; KOJIMA, Hirotsugu3
1Toyama Prefectural University, 2 National Institute of Polar Research, 3 RISH, Kyoto University
According to PIC simulations, ESW (Electrostatic Solitary Waves) aregenerated from electron beam instabilities. ESW correspond the upper
frequency component of BEN (Broadband Electrostatic Noise) which isfrequently observed in space plasma. The generation mechanism of thelow frequency component of BEN, however, is still unexplained.
To clarify whether such low frequency waves are generated, we madestatistical analysis on generation conditions of low frequency componentof BEN observed by Electric Field Detector (EFD) onboard Geotail
spacecraft. We detected low frequency component of BEN automaticallyfrom EFD data, and made an occurrence frequency distribution of thesewaves. Low frequency component of BEN are observed in PS and PSBL region
in the magnetosphere.
We studied several plasma parameters at the time when low frequency
component of BEN were observed, and found that these waves were observedin the conditions with low ion density and strong B field in theseregions. Then, based on these statistical analysis, we are going toperform a series of three-dimensional electromagnetic particle
simulations with different parameters on PC-Cluster built in ourlaboratory.

Keywords: particle simulations, low frequecy component of BEN, Geotail, EFD

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PEM26-P10

Room:Convention Hall

Time:May 24 18:15-19:30

Test-particle simulation of electron elastic collision with neutral H2O molecule originatedfrom Enceladus
TADOKORO, Hiroyasu1∗ ; KATOH, Yuto21

Tokyo University of Technology, 2 Tohoku University

Water group neutrals (H2 O, OH, and O) in Saturn’s inner magnetosphere play the dominant role in loss of energetic electrons
and ions because of abundance of the neutral particles [e.g., Paranicas et al., 2007; Sittler et al., 2008]. The observations ofinjected electrons and ions in the inner magnetosphere suggest that these particles do not survive very long time due to theneutral cloud originated from Enceladus [e.g., Paranicas et al., 2007; 2008]. Thus, the previous study suggested that the neutral
cloud contributes to loss processes of plasma in the inner magnetosphere. However, little has been reported on a quantitative
study of the electron loss process due to electron-neutral collisions.
In the present study, we examine the variation of energetic electron pitch angle distribution at the magnetic equator and loss rateof precipitated electrons into Saturn’s atmosphere through pitch angle scattering due to elastic collisions with neutral H2 O along
Saturn’s dipole magnetic field line around Enceladus. We conduct one dimensional test-particle simulation for monoenergetic
electrons along Saturn’s dipole magnetic field line around Enceladus when the co-rotating electron flux tube passes the dense
H2 O region in the vicinity of Enceladus (˜6.4 minutes). The initial electron pitch angle distribution is assumed to be isotropic. In
case of 1 keV electron, Tadokoro et al., [2014] showed that
1. the equatorial electron pitch angle distribution near the loss cone (<20 degrees and >160 degrees) decreases with timethrough pitch angle scattering due to elastic collisions and that the distribution around 90 degrees shows significant scattering
due to the dense region of H2 O,
2. It is found that the electrons of ˜19 % to the total number of equatorial electrons at the initial condition are lost in ˜380
seconds.
3. The calculated loss time is fourth faster than the loss time under the strong diffusion.
We also show the loss rates through pitch angle scattering of electrons with not only 1 keV but also several hundreds eV ?
several tens of keV.

Keywords: Test particle simulation, elastic collision, Enceladus, Saturn

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PEM26-P11

Room:Convention Hall

Time:May 24 18:15-19:30

Ion kinetic effects to nonlinear processes of the Kelvin-Helmholtz instability
UMEDA, Takayuki1∗ ; UENO, Satoshi1 ; NAKAMURA, Takuma2
1-Terrestrial Environment Laboratory, Nagoya University, 2 Space Research Institute, Austrian Academy of Sciences

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 astrong 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 scaleis 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 secondaryinstabilities occurring in the nonlinear stage of the primary KHI show different evolutions depending on the sign of the innerproduct between the magnetic field and the vorticity of the velocity shear layer. The difference of the nonlinear evolution
depending on the ion-to-electron mass ratio is also discussed.

Keywords: Kelvin-Helmholtz instability, computer simulation, Vlasov equation, non-MHD

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