PEM19-01

Japan Geoscience Union Meeting 2016

Microinstabilities in a supercritical perpendicular shock revisited*Shuichi Matsukiyo1, Takayuki Umeda2
1.Kyushu University, 2.Nagoya University
It is considered that reflected ions play decisive roles in the dissipation processes at asupercritical collisionless shock. Local non-equilibrium plasma distribution function in the footof a perpendicular shock leads to a variety of microscale instabilities. Two of the major
instabilities which have been extensively studied for the parameters of typical heliospheric shocks
are the electron cyclotron-drift instability and the modified two-stream instability. They havebeen often discussed separately, because of the large difference in dominant wave frequency between
them. Although only a few of the past studies tried to examine the nonlinear evolutions andcompeting processes of them, the physical parameters used in the past numerical simulations were
not realisitic. The relative importance of the instabilities may be a function of ion-to-electronmass ratio as well as the ratio of electron plasma to cyclotron frequiencies, while these two
ratios are hard to be simultaneously realistic in a full particle-in-cell simulation due to thelimited computational resources.
In this study microinstabilities in the foot of a supercritical perpendicular shock is revisited.
We perform a number of local simulations representing a part of the foot region with systematicallychanging the two ratios, mass ratio and frequency ratio, by using two-dimensional fullparticle-in-cell code. The foot plasma is assumed to be consist of incoming ions, electrons, andreflected ions. The system size is smaller than ion gyro radius in X, which is parallel to theshock normal, and a few times ion inertial length in Y, which is along a shock surface and theambient magnetic field. The boundary conditions are periodic in both directions. We will report theresults of the simulations in which the mass ratio and the frequency ratio are systematicallyvaried with fixing the local Alfven Mach number, plasma beta, and relative density of the reflectedions.
Keywords: collisionless shock, microinstability, numerical simulation©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-01 -PEM19-02

Japan Geoscience Union Meeting 2016

Second order Fermi acceleration of ions in the earth's foreshock: wave dispersion effects*Fumiko Otsuka1, Shuichi Matsukiyo1, Tohru Hada1
1.Interdisciplinary Graduate School of Engineering Sciences Kyushu University
It is well known that the second order Fermi acceleration can efficiently operate when there exist
multiple electromagnetic waves traveling in two opposing directions. The process has been discussed
using turbulence composed of non-dispersive Alfven waves (e.g., Terasawa, 1989; Kuramitsu and Hada,
2000), and has been applied to ion acceleration in the earth's foreshock. However, upstream waves
in the earth's foreshock have a wide frequency spectrum extending beyond the ion cyclotron
frequency, where the effects of finite wave dispersion cannot be neglected.
In this presentation, we discuss the second order Fermi process by performing test particle
simulations, paying particular attention to the effects of finite wave dispersion on the ion
acceleration efficiency. We consider the right- and left-hand polarized electromagnetic waves, withboth parallel and anti-parallel propagation directions along the background magnetic field. A
power-law spectrum of each wave component is assumed. The waves obey the cold plasma dispersion
relation. We evaluate the acceleration efficiency as a function of the initial ion kinetic energy.
We will discuss implications of our results to Cluster observations (Kis et al., 2004).
Keywords: second order fermi acceleration, particle acceleration and energy diffusion, wave
dispersion©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-02 -PEM19-03

Japan Geoscience Union Meeting 2016

Density estimation utilizing the group-standing frequency of upstream whistlers in thesolar wind
*Yasunori Tsugawa1, Yuto Katoh2, Naoki Terada2, Shinobu Machida1
1.Institute for Space-Earth Environmental Research, Nagoya University, 2.Graduate School of
Science, Tohoku University
Upstream whistlers, so-called 1 Hz waves, have been observed in upstream regions of most solar
system bodies including Mercury, Venus, Earth, the Moon, Mars, Saturn, and Uranus [e.g., Orlowski
and Russell, 1995; Russell, 2007]. Their frequencies in the spacecraft frame concentrate around 1
Hz at 1 AU and slightly decrease with distance from the Sun. They exhibit similar spectral
properties even in different situations, suggesting that common generation and propagation
processes are responsible for the waves throughout the solar system.
Based on statistical and comparative studies, we proposed that the waves are essentiallygroup-standing, i.e., their group velocities become rather small in the body's rest frame [Tsugawa
et al., JGR 2014]. In the group-standing condition, the waves can behave as if they are at aresonance frequency because the group refractive index approaches infinity in the spacecraft /solar system body rest frame. This suggests that the group-standing frequency can be utilized as anindicator of plasma parameters, in analogous to the upper-hybrid resonance frequency, which is used
to determine the plasma density in the magnetosphere. We propose a method to estimate the plasma
density utilizing the group-standing frequency and evaluate the feasibility of the proposed methodby using Geotail in-situ observations. The method possibly estimates the absolute value of number
density with an accuracy of <~0.1, although there remains some considerable difficulties. We
discuss pros and cons of the proposed method.

©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-03 -PEM19-04

Japan Geoscience Union Meeting 2016

Comparison between Polarization and Spectral Characteristics
of Zebra Pattern in Solar Radio Bursts*Kazutaka Kaneda1, Hiroaki Misawa1, Kazumasa Iwai2, Fuminori Tsuchiya1, Takahiro Obara1
1.Planetary Plasma and Atmospheric Research Center, Graduated School of Science, Tohoku University,
2.National Institute of Information and Communications Technology
Zebra pattern (ZP) is one of the spectral fine structures superimposed on the broadband type IV
continuum, which has a characteristic spectral pattern with a number of parallel drifting stripes.
Since these spectral fine structures reflect their emission mechanisms, we can obtain informationfrom their characteristics about physical processes such as particle acceleration, excitation ofelectrostatic waves and their conversion to electromagnetic waves. Polarization of emission isimportant to know its emission mechanism. However, the relationship between spectral
characteristics of ZP and its polarization has not been understood. In this study, we aim to reveal
the generation mechanism of ZP by investigating their polarization characteristics.
In Kaneda et al. (2015, ApJL), we analyzed polarization characteristics of a ZP event and suggested
from its frequency dependence that the ZP was originally generated polarized in the O-mode and waspartly converted into the X-mode near the emission source. In order to examine these results, weanalyzed totally 17 ZP events observed with AMATERAS, a solar radio telescope developed by Tohoku
University in the frequency range of 100-500 MHz (Iwai et al., 2012). The analysis was made focusedon three aspects: degree of circular polarization, temporal delay between the two polarization
components and frequency separation between adjacent stripes. We derived these three parameters
using highly resolved spectral data from AMATERAS. As a result, we found the following
characteristics; degree of polarization in the range of 10-80%, temporal delay of 0-70 ms andfrequency separation of 1-5 MHz, and that these characteristics of ZP were rather different fromevent to event. The difference in these parameters implies the difference in physical mechanisms at
a certain stage of the generation of ZP emission. Based on the obtained results, possible
generation mechanisms of ZP will be discussed.
Keywords: Solar corona, Radio bursts, polarization, AMATERAS©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-04 -PEM19-05

Japan Geoscience Union Meeting 2016

Injection of solar wind electrons into the plasma void and associated magnetic
fluctuations in the ELF range*Tomoko Nakagawa1, Hideo Tsunakawa2, Yoshifumi Saito3, Masaki N Nishino4
1.Information and Communication Engineering, Tohoku Institute of Technology, 2.Deparment of Earthand Planetary Sciences, Tokyo Institute of Technology, 3.Solar System Science Division, ISAS, JAXA,
4.Institute for Space-Earth Environmental Research, Nagoya University
Generation mechanism of the magnetic fluctuations in the ELF range detected by MAP-LMAG
magnetometer onboard Kaguya in the deepest wake behind the moon associated with the type-II entry
protons is studied. Most of the waves were detected on the magnetic field lines which were notconnected with the lunar surface, along which the solar wind electrons were injected into the wake.
The waves had compressional components of field variation, suggesting that the direction of the
wave number vector was oblique with respect to the background magnetic field. Interaction between
the field-aligned hot electron beam and oblique whistler and electrostatic waves is considered.
Keywords: electron beam, magnetic field variation, lunar wake, type II entry protons, whistler mode
wave, oblique propagation©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-05 -PEM19-06

Japan Geoscience Union Meeting 201610-sec magnetic field enhancement detected by Kaguya orbiting around the moon in the solar
wind
Yoko Karibe1, Takeshi Miyazawa1, Kentaro Murakami1, *Tomoko Nakagawa1, Hideo Tsunakawa2
1.Information and Communication Engineering, Tohoku Institute of Technology, 2.Deparment of Earthand Planetary Sciences, Tokyo Institute of Technology
Short-period magnetic enhancements were detected by LMAG magnetometer onboard Kaguya spacecraft
orbiting the moon in the solar wind. The magnitude of the magnetic field enhanced up to 1.5 to 3.6
times as large as that of the preceding quiet periods which lasted for more than 5 minutes. The
duration of the enhancements was specifically 10 seconds, ranging from 8 to 46 sec. Some of themshowed rotation of the magnetic field, but the others did not. The short-period magnetic
enhancements were not detected above the major magnetic anomaly of the moon. They were not detectedrecursively on the same location on the moon. They were found both on the dayside and nightside of
the moon, with a slight preference above the terminator. Similar magnetic field enhancement was
searched for in the simultaneously observed solar wind magnetic field data obtained by GEOTAIL
spacecraft, but no intensification of the magnitude was found although similar waveforms of eachmagnetic field components were found. At present, it is not certain whether they originate from thelunar crustal field, the solar wind, or the interaction between them.
Keywords: Kaguya/LMAG, solar wind, magnetic enhancement, 10sec©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-06 -PEM19-07

Japan Geoscience Union Meeting 2016

Spherical Harmonic Expansion of Solar Wind Speed*Kazuyuki Hakamada1, Munetoshi Tokumaru 2, Ken'ichi Fujiki2
1.Department of Natural Science and Mathematics, Chubu University, 2.Institute for Space-EarthEnvironmental Research, Nagoya University
The Institute for Space-Earth Environmental Research, Nagoya University has observed solar windspeed (SWS) by the interplanetary scintillation (IPS) method. Drs. Tokumaru and Fujiki have been
constructing synoptic charts of SWS by the technique of Computerized Axial Tomography (CAT). SWS
synoptic charts show the distribution of solar wind speed on the spherical surface sorrounding thesun named "source surface"; the ordinate shows solar latitude and the abscissa shows Carrington
longitude in the chart. We can get one synoptic chart during every one solar rotation called
Carrington rotation. The spatial resolution of this chart is one degree for both in longitude andin latitude. We frequently found wide region of data gap in the chart, especially in highlatitudes. In this paper, in the first, (1) we try to expand the SWS on the synoptic chart into
spherical harmonic series (N=0--90, M = 0--N) and to calculate about (90 x 90) coefficients (Anmand Bnm) of expansion series. And next, (2) we try to estimate continuously the SWS in both thedirection of longitude and the one of latitude in the synoptic chart. It is found that thistechnique can estimate well the SWS, especially in low latitudes of chart.
Keywords: Solar Wind Speed, Source Surface, Spherical Harmonic Function©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-07 -PEM19-08

Japan Geoscience Union Meeting 2016

Comparison of calculated and observed IMF near magnetic cloud start times*Nobuhiko Nishimura1, Nishiki Nozaki1, Bernard Jackson2, Hsiu-Shan Yu2, Munetoshi Tokumaru1,
Ken'ichi Fujiki1, keiji hayashi1, Kazuyuki Hakamada3
1.Institute for Space Earth Environmental Research., 2.University of California, San Diego.,
3.Chubu University.
The solar source of magnetic clouds (MCs) is considered to be either coronal mass ejections (CMEs)
or prominence eruptions [Bothmer et al., 1994, 1998]. We suppose that the coronal magnetic fields
above CME or prominence eruption sites move outward and are then convected into interplanetary
space to arrive at the Earth a short time before the MC start time. We extract the magnetic fieldclose to the solar surface at different heights using the PFSS model [Hakamada, 1998] and propagate
this field outward to 1 AU using 3D-reconstructed solar wind velocity [Jackson et al., 2010]. The
purpose of our work is to examine whether the direction of interplanetary magnetic field (IMF)
agrees with the observed vector field prior to a MC arrival at the Earth. We compare the sign ofeach component of modeled IMF (in RTN coordinates) with that of IMF observed by ACE three hours
before the MC start time (pre MC time) and at the MC start time (MC time). These comparisons are
made for six MC events during 2006 - 2007. We find that the sign of Bn, the normal component of IMF
in RTN coordinates, extracted from 1.4 Rs (1.2 Rs) agrees best with ACE observations at the pre MC
time (at the MC time) for all MC events analyzed here. However, the other two components Br and Bt, the radial and tangential components of IMF in RTN coordinates, extracted from 1.4 Rs (1.2 Rs) do
not agree as well with ACE observations at the pre MC time (at the MC time). We conclude that Bn
observed by ACE at the pre MC time (at the MC time) is related to that at 1.4 Rs (1.2 Rs) at thelocation of the sub-Earth point on the Sun. This result shows that we can infer the sign of Bn at
the MC time (pre MC time) from the value present at 1.2 Rs (1.4 Rs) at the location of the
sub-Earth point, and thus this is an important finding for space weather forecasts. Future work
will extend this result to additional MC events.
Keywords: coronal magnetic field, magnetic cloud, space weather, solar wind©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-08 -PEM19-09

Japan Geoscience Union Meeting 2016

A Statistical Study of the Radial and North-South Component Values of Heliospheric
Magnetic Field*Nishiki Nozaki1, Nobuhiko Nishimura1, Bernard Jackson2, Hsiu-Shan Yu2, Munetoshi Tokumaru1,
Ken'ichi Fujiki1, keiji hayashi1, Kazuyuki Hakamada3
1.Institute for Space-Earth Environmental Research, 2.University of California, San Diego, 3.Chubu
University
Determination of interplanetary magnetic field (IMF) north-south component of magnetic field (Bz)
is important from the space weather perspective because this field interacts with Earth’s magnetic
field causing geomagnetic storms. Lyatsky et al. (2003) and Youssef et al. (2011) show that there
is a correlation between IMF Bz (south is positive) and the absolute value of the radial field Bx(|Bx|) during solar minima. They find a positive correlation when the dominant solar field has apositive polarity and negative for a dominant negative field polarity. The negative and positive
polarities correspond to whether the Sun’s magnetic field in the northern hemisphere is directed
toward or away from the Sun, respectively. We calculate the correlation between IMF Bz and |Bx|using the OMNI dataset from 1965 - 2015, and Helios in-situ measurement data from 1975 - 1977. In asimilar study, we find that the correlation between Bz and |Bx| shows a sinusoidal variation
associated with ~11 year solar cycle, and also that an even more significant correlation between Bz
and |Bx| exists for solar distances between 0.3 and 0.4 AU in the Helios measurements. In an
ongoing study, we extrapolate the Potential Field Source Surface (PFSS) model [Hakamada, 1998] tothe Earth’s location by using the UCSD 3D tomography model [Jackson et al. 2010] and compare theradial component (Br) of modeled magnetic field with the normal (north-south) component (Bn)observed by ACE spacecraft. This study finds a significant positive correlation between Br and Bn(north is positive). Thus, this study strongly suggests that the IMF Bz is generated, not ininterplanetary space, but at the corona. In the future, we will study why this correlation between
Bz and |Bx| exists.
Keywords: solar wind, interplanetary magnetic field, space weather, heliosphere©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-09 -PEM19-10

Japan Geoscience Union Meeting 2016

Analysis of solar wind turbulence using interplanetary scintillation measurements*Munetoshi Tokumaru1
1.Institute for Space-Earth Environmental Research, Nagoya University
The power spectrum of interplanetary scintillation (IPS) provides with crucial information on
physical properties of the solar wind turbulence with a spatial scale of ~100-~10 km; so-calledmicro-turbulence. In this study, the spectral index and anisotropy of the solar wind turbulence aredetermined by fitting a theoretical model to IPS spectra observed for two strong sources 3C273 and3C48 with the Solar Wind Imaging Facility Telescope (SWIFT) of the Institute for Space-EarthEnvironmental Research (ISEE), Nagoya University. In this fitting analysis, free parameters are thepower-law index of the turbulence spectrum, the axial ratio of the anisotropy, and the turbulence
level. The solar wind speed derived ISEE multi-station IPS observations is used as a fixedparameter to calculate the IPS spectrum model. The apparent size of IPS sources is another fixedparameter, and 60 mas and 100 mas are used for 3C273 and 3C48, respectively. The spectral indicesobtained here (4.1+/-0.7) are close to but slightly higher than the Kolmogorov value (11/3), andthe axial ratios (1.0+/-0.4) are nearly equal to a unity, suggesting that the turbulence isisotropic. The important point to note here is that there is a significant negative correlation
between spectral indices and axial ratios; i.e. the turbulence spectrum becomes flatter, as it
becomes more anisotropic. The spectral indices and axial ratios are also compared with solar windspeeds, and poor (positive) correlations are found between them. These results are unchanged when
the solar wind speed is assumed to be a free parameter in the fitting analysis.
Keywords: solar wind, interplanetary scintillation, turbulence©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-10 -PEM19-11

Japan Geoscience Union Meeting 2016

Turbulent transport model in a three-dimensional structured solar wind
*Daikou Shiota1, Gary P. Zank2, Laxman Adhikari2, Peter Hunana2
1.Institute for Space and Earth Environmental Research, Nagoya University, 2. Center for Space
Plasma and Aeronomic Research (CSPAR) and the Department of Space Science, The University of
Alabama in Huntsville, USA
Turbulence plays an essential role in the heating of coronal and solar wind plasma and theacceleration of the solar wind, as well as acceleration of energetic particles associated withinterplanetary shocks. Turbulence can be produced by energetic particles and shocks and the radial
and lateral inhomogeneity of the global interplanetary magnetic field and solar wind plasma
distribution. Because of the close coupling of turbulence, plasma heating, the global solar windstructure, and energetic particles, a comprehensive model describing not only turbulence but also
the large-scale inhomogeneity of the solar wind and the interplanetary magnetic field is necessary
to understand the physics of these phenomena.
Recently we have developed a solar wind MHD model for the inner heliosphere based on synoptic
observations of the photospheric magnetic field (Shiota et al. 2014). The numerical results show
reasonable agreement with in situ measurements of the solar wind at the orbits of Earth, Venus, andMars. This MHD model is now used as part of the real-time space weather forecast system SUSANOO(http://st4a.stelab.nagoya-u.ac.jp/susanoo/).
We have extended our 3D MHD model to include the transport and dissipation of turbulence using thetheoretical model developed by Zank et al. (2012). We solve a coupled model that describes the 3D
inhomogeneous solar wind and the temporal and spatial evolution of three moments or variables that
describe turbulent fluctuation intensities (the energy in forward and backward modes and theresidual energy) and their corresponding correlation lengths. We find that the radial profiles forthe three moments of the solar wind turbulence predicted by our model show good agreement withthose of in situ measurements obtained from Ulysses and Helios observations. Based on the detailed
analysis of the numerical results, we will discuss the connection between turbulence generation andglobal solar wind structure.
Keywords: solar wind , MHD, turbulence©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-11 -PEM19-12

Japan Geoscience Union Meeting 2016

A Test-Particle Simulation of ISM Oxygen over Heliosphere and Analysis for IBEX
observations*Akito Davis Kawamura1
1.Kwasan Observatory, Kyoto University
The result of a test particle simulation will be presented and discussed as a possible
interpretation on Interstellar Boundary EXplorer (IBEX) observations of InterStellar Medium (ISM)
Oxygen. Due to the physical characteristics of Oxygen atom, neutral Oxygen had interacted with
Hydrogen-dominated Heliosphere before they were observed by IBEX, and such Oxygen may contain some
information of Heliospheric structure within its flux distribution over the sky. In order tounderstand this observation, we must classify the particles based on their histories ofinteractions with Heliosphere. We provide a unique classification on the test particles which makes
the simulation result provide an insight on the IBEX observations.
Keywords: Heliosphere, Heavy particle, Interstellar Boundary EXplorer (IBEX)©2016. Japan Geoscience Union. All Right Reserved.

- PEM19-12 -