PEM08-01

Room:302

Time:May 26 14:15-14:35

Energetic Particle Acceleration in the Inner Magnetosphere by ULF waves excited byinterplanetary shock
ZONG, Qiugang1∗
1School of Earth and Space Sciences Peking Univ.

When an interplanetary shock or a solar wind dynamic pressure impulse impinges on the magnetophere, ultra low-frequency(ULF) waves can be excited in the magnetosphere and the solar wind energy can be transported from interplanetary space into
the inner magnetosphere.
In this study, we have systematically studied ULF waves excited at in the magnetosphere by interplanetary shock or solar winddynamic pressure impulse. We have found that the poloidal and toroidal waves excited by positive and negative pressure pulses
oscillate in a similar manner of phase near 06:00 local time (MLT) and 18:00 M LT, but in antiphase near 12:00 M LT and 0:00
MLT. Furthermore, it is shown that excited ULF oscillations are in general stronger around local noon than those in the dawn
and dusk flanks. It is demonstrated that the poloidal wave amplitudes are stronger than the toroidal wave amplitudes except in
the magnetotail.
We have investigated the response of the Earths ring current ions including oxygen ions to ULF waves induced by interplanetaryshocks. Both Earths ring current ions - hydrogen and oxygen ions are found to be accelerated significantly with their temperatureenhanced by a factor of two and three immediately after the shock arrival respectively. Multiple energy dispersion signatures ofring current ions were found in the parallel and anti-parallel direction to the magnetic field immediately after the interplanetaryshock impact. The energy dispersions in the anti-parallel direction preceded those in the parallel direction. Multiple dispersion
signatures can be explained by the flux modulations of local plasmaspheric ions (rather than the ions from the Earths ionosphere)
by ULF waves. It is found that both cold plasmaspheric plasma and hot thermal ions (10 eV to 40 keV) are accelerated anddecelerated with the various phases of ULF wave electric field. We then demonstrate that ion acceleration due to the interplanetaryshock compression on the Earths magnetic field is rather limited, whereas the major contribution to acceleration comes from theelectric field carried by ULF waves via drift-bounce resonance for both the hydrogen and oxygen ions. The integrated hydrogenand oxygen ion flux with the poloidal mode ULF waves are highly coherent (>0.9) whereas the coherence with the toroidal
mode ULF waves is negligible, implying that the poloidal mode ULF waves are much more efficient in accelerating hydrogenand oxygen ions in the inner magnetosphere than the toroidal mode ULF waves.

Keywords: Energetic particle, ULF waves, Inner magnetosphere, Acceleration, Wave-Particle Interaction

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PEM08-02

Room:302

Time:May 26 14:35-14:55

Impact of High-Energy Particle Precipitation on the Upper Atmosphere
TURUNEN, Esa1∗
1

SGO, University of Oulu, 2 STEL, Nagoya University

Various forms of high energy particle precipitation into atmosphere present a coupling process between atmospheric layers
and near-Earth space, where energy input into atmosphere is often controlled not only by the original source of the particles,
but also by interactions occuring in the inner magnetosphere. Here we first review shortly the impact of energetic particles inatmosphere in general, and present the current status of knowledge in chemical variations of atmosphere caused by these particles,
including galactic cosmic rays, solar protons and electrons of magnetospheric origin. The effects are both direct and indirect by
first generating chemically active minor constituents of the atmosphere, such as odd nitrogen and odd hydrogen, which in turncan affect atmospheric ozone via catalytic reactions either directly in-situ, or after transport in atmosphere to lower altitudes andlower laitudes. Then we discuss recent advance in studying the effects of high-energy electron precipitation (EEP) in atmosphere,
the global role of which still is quantitatively largely unknown. Recent published research has shown evidence about energetic
electron precipitation causing statistically significant decrease of upper stratospheric and mesospheric ozone during extended
periods of time, so that one would need to include EEP as a process in general atmospheric circulation models, if we wantto understand our atmosphere as a whole. It is pointed out how importantly we need new measurements characterizing moreaccurately the energy and flux, as well as spatial and temporal variations of the energetic electron precipitation, both at high andsubauroral latitudes. Such new data would be given by the Japanese ERG satellite mission. Combined studies using groundbased measurements and theoretical modeling together with ERG mission measurements, are outlined.
Keywords: high-energy particle, energetic electron precipitation, atmospheric chemistry, magnetosphere, ionospheric modelling,
ERG satellite

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PEM08-03

Room:302

Time:May 26 14:55-15:10

A method for direct measurements of wave-particle interactions in the Earth’s inner magnetosphere
KITAHARA, Masahiro1∗ ; KATOH, Yuto1
1

Dept. Geophys., Grad. Sch. Sci., Tohoku Univ.

Whistler-mode chorus emissions are one of frequently-observed plasma waves in the Earth’s inner magnetosphere. Generally,
chorus emissions are characterized by a sequence of intense and coherent emissions with frequency shift. Chorus emissions are
generated near the magnetic equator by nonlinear wave-particle interactions and are emerged from whistler-mode waves generated through an instability driven by a temperature anisotropy of energetic electrons in the kinetic energy range from a few to tensof keV. Chorus emissions have a potential to accelerate relativistic electrons from the kinetic energy range of several hundred keV
to a few MeV. Furthermore, chorus emissions induce the pitch angle scattering of energetic electrons and relativistic electrons.
Precipitation of electrons as a result of the pitch angle scattering is one of candidate processes causing diffuse or pulsating auroras
observed at the ground. A number of previous studies treat the acceleration (or wave-generation) and the pitch angle scatteringof energetic electrons as the diffusion problem of the phase space density and calculate the diffusion coefficients from the wave
spectrum. However, the location where the wave-particle interaction occurs efficiently has not been identified yet by the direct
observation. Direct measurements of both the energy exchange and the pitch angle scattering of energetic electrons contributethe thorough understanding of wave-particle interactions in the Earth’s inner magnetosphere.
Fukuhara et al. (2009) proposed Wave-Particle Interaction Analyzer (WPIA), which is a new instrumentation measuring a relative phase angle between a wave magnetic field vector and a velocity vector of each particle and calculates the energy exchange
between waves and particles. The WPIA, which enables us to directly detect wave-particle interactions in space plasmas, will
be installed on the ERG satellite of JAXA/ISAS. Katoh et al. (2013) formulated measurable values of the WPIA as the Jouleheat Wint and discussed the feasibility of measuring Wint . In the present study, in addition to the method to detect the energy
exchange, we propose a method to directly detect the pitch angle scattering of resonant particles. The method is calculating G
that is the pitch angular component of the time variation of the momentum of particles.
We apply the proposed method to results of the one-dimensional electron hybrid simulation reproducing the generation processof chorus emissions around the magnetic equator [Katoh and Omura, 2007]. In the result of the analysis, we obtain significant
values of G for electrons in the kinetic energy and pitch angle ranges satisfying the cyclotron resonance condition with thereproduced chorus emissions. We compared the result of the analysis of G with the temporal variation of both the pitch angle distributions and the wave spectra observed at fixed points in the simulation. While the velocity distribution function varies similarly
in both hemispheres, the obtained time variation of the momentum is only significant in the pitch angle range corresponding toelectrons moving northward (southward) in the southern (northern) hemisphere, indicating the pitch angle scattering of electrons
by chorus emissions propagating away from the equator. The results of the present study demonstrate that the proposed method
enables us to identify the location where wave-particle interactions occur in the simulation system. Furthermore, we re-examine
the formula of the measurement values Wint to detect the energy exchange, based on the discussion of the quantity G.
Keywords: whistler-mode chorus emissions, pitch angle scattering, WPIA, ERG mission, electron acceleration, wave-particle
interactions

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PEM08-04

Room:302

Time:May 26 15:10-15:25

Characteristics of drift resonance in the outer radiation belt with Pc5 waves based on
GEMSIS-RC and RB simulations
KAMIYA, Kei1∗ ; SEKI, Kanako1 ; SAITO, Shinji1 ; AMANO, Takanobu2 ; MIYOSHI, Yoshizumi1 ;MATSUMOTO, Yosuke3 ; UMEDA, Takayuki1
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 University of Tokyo, 3 Chiba University

Radial transport of relativistic electrons due to Ultra Low Frequency (ULF) waves in the Pc5 frequency range (1.67mHz 6.67mHz) is one of important candidates to accelerate and decelerate the outer radiation belt electrons. It is considered as aresult of the drift resonance process caused by a resonant interaction between the magnetic drift motion of electrons in the
dipole-dominated magnetic field configuration and the electromagnetic fluctuations of Pc5 waves. The Pc5 amplitude decreases
rapidly with decreasing radial distance, and the recent studies has pointed out that the efficiency of radial transport caused by the
Pc5 waves can be highly depending on the characteristics of the waves [e.g., Ukhorskiy and Sitnov, 2008]. They indicated thatcollective motion of the outer belt electrons can exhibit large deviations from radial diffusion. Thus, it is important to understandthe fundamental behavior of collective motion of the electrons against the Pc5 waves in the inner magnetosphere.
In this study, we combine two simulation models of the inner magnetosphere: GEMSIS-RC (ring current) and RB (radiationbelt) models. The GEMSIS-RC model is a self-consistent and kinetic numerical simulation code solving the five-dimensional
collisionless drift-kinetic equation for the ring-current ions in the inner-magnetosphere coupled with Maxwell equations [Amanoet al., 2011]. The GEMSIS-RB code conducts test particle trajectory tracings of relativistic electrons in arbitrary magnetic
and electric field configurations [Saito et al., 2010]. Hence, we can conduct Pc5 wave simulation with GEMSIS-RC, and thenthe obtained time variations of the magnetic and electric fields are used as an input to GEMSIS-RB code to understand thetransport of relativistic electrons due to the Pc5 waves. For simplicity, we investigated effects of monochromatic wave on thedrift resonance. Using the simulation results, we evaluated between radial profiles of electron phase space density. The results
show that the resonant electrons continuously obtain or lose energy, but the range of energy variation due to the drift resonant
scattering of relativistic electrons are wider in the simulation than in the simple theoretical estimations. It is also shown that theseelectrons have local peaks in the radial distribution in phase space density. This implies the non-linear effect due to the variationof electrons’ drift velocity must be considered in the radiation belt.
Keywords: Radiation belt electrons, Drift resonance, Pc5 waves, GEMSIS-RC and RB simulations

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PEM08-05

Room:302

Time:May 26 15:25-15:40

Cold M/Q=2 ion distribution in the inner magnetosphere estimated from lightning-induced
EMIC waves observed by Akebono
MATSUDA, Shoya1∗ ; KASAHARA, Yoshiya1 ; GOTO, Yoshitaka1
1

Kanazawa University

Ion cyclotron whistlers are electromagnetic ion cyclotron (EMIC) mode waves induced by lightning discharge. They are generated by mode conversion from lightning whistler waves to EMIC waves. It is well known that their propagation characteristics
can be explained by the dispersion relation. Particularly, the dispersion relationship of EMIC, or determination of the bands thatcan be propagated by EMIC, depends strongly on the ion composition of the plasma. Hence, information on the variation of ioncomposition can be obtained through ion cyclotron whistler wave observation.
In our previous study, we found that M /Q = 2 ion cyclotron whistlers were frequently observed by the Akebono satellite at
an altitude region around 3100-10000 km. In the current study, we examine spatial occurrence distributions of observed ion cyclotron whistler wave. We detected 845 H+ , 933 M /Q = 2 ion, 1888 He+ band ion cyclotron whistler waves by visual inspection
during the period from March 1989 to September 1995. It is found that each band of ion cyclotron whistler wave was observed inalmost exclusive regions. We explain these characteristics by considering the wave generation mechanism along the geomagnetic
field line. We estimate ion composition by considering the conditions necessary for ion cyclotron whistler generation, and wedetermine that a certain amount of M /Q = 2 ions exist at the restricted L shell region in the plasmasphere.
We show that the spatial occurrence distribution of observed M /Q = 2 ion cyclotron whistlers changes depending on the magnetic local time. It is determined that a certain amount of M /Q = 2 ions exist at L inside 2.4 in the local dayside and inside 3.0
in the local nightside. Therefore, there seems to be the density enhancement process in the local nightside region.

Keywords: ion cyclotron whistler, EMIC wave, M/Q = 2 ion, ion composition, Akebono satellite, inner magnetosphere

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PEM08-06

Room:302

Time:May 26 15:40-15:55

Spatial and temporal variation of Sub-Auroral Polarization Streams: Initial results fromthe SuperDARN HOP radars
NISHITANI, Nozomu1∗ ; HORI, Tomoaki1
1

Solar-Terrestrial Environment Laboratory, Nagoya University

Super Dual Auroral Radar Network (SuperDARN) is a network of HF radars deployed in both hemispheres. The SuperDARN
Hokkaido West radar, one of SuperDARN HOkkaido Pair of (HOP) radars, is the newest SuperDARN radar located in Rikubetsu,
Hokkaido, Japan, which began its operation in October 2014. Longitudinal coverage of subauroral ionosphere over several hoursof magnetic local time by the SuperDARN HOP radars, together with other midlatitude SuperDARN radars, will enable us to
study the detailed characteristics of Sub-Auroral Polarization Streams (SAPS), and to find clues to their generation, growth anddecay mechanisms. In this paper initial results of the SuperDARN Hokkaido Pair of (HOP) radars observation of SAPS, withfocus on the location / timing of SAPS activity relative to geomagnetic activity such as substorms, will be presented.
Keywords: SuperDARN HOP radars, sub-auroral polarization streams, substorm

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PEM08-07

Room:302

Time:May 26 16:15-16:35

Recent results from the NASA Van Allen Probes and the NSF FIREBIRD missions
SPENCE, Harlan1∗
1

University of New Hampshire

The NASA Van Allen Probes began its two-year prime science mission phase following its launch into the inner magnetospherein August 2012. Designed to study and understand radiation belt structure and dynamics ideally to the point of predictability, thedual-spacecraft Van Allen Probes mission comprises a comprehensive suite of charged particle and fields measurements neededto achieve closure on critical science questions. The Radiation Belt Storm Probes ? Energetic Particle, Composition, and Thermal
Plasma (RBSP-ECT) suite consists of three primary instrument types that collectively provide clean, robust measurements of theelectrons and key ions in the inner magnetosphere, with high energy spectral and pitch angle resolution, spanning energy ranges
covering the cold/warm plasmasphere populations, the hot ring current populations, the medium-energy electron seed population, as well as the core relativistic and ultra-relativistic radiation belt populations. The Van Allen Probes orbit near the magnetic
equator, optimized for probing the source regions of particle acceleration and the location through which virtually all particles
must pass. However, because the atmospheric loss cone is so small at the magnetic equator, even such an ambitious mission
cannot completely explore that loss process without additional measurements away from the magnetic equator. In a complimentary fashion, the NSF Focused Investigation of Relativistic Electron Burst Intensity Range and Dynamics (FIREBIRD) mission
orbits at low altitudes, measuring radiation belt electrons precipitating into the atmosphere. The twin FIREBIRD spacecraft
were launched in late January 2015 when they began probing the spatial-temporal variability of electron precipitation from theradiation belt. In this paper, we provide a summary of the science accomplishments from the combined RBSP-ECT instrument
suite and FIREBIRD missions, specifically focusing on radiation belt loss processes.
Keywords: Radiation Belt, Inner Magnetosphere, Particle Precipitation

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PEM08-08

Room:302

Time:May 26 16:35-16:50

Data assimilation of ionospheric magnetic field perturbations into a global magnetospheric model.
KONDRASHOV, Dmitri1∗ ; MERKIN, Slava2
1

University of California, Los Angeles, 2 John Hopkins University, USA

Ionosphere is tightly coupled with the magnetosphere and is the only region of geospace where in situ observations approaching global scale are possible. This capability is owing to the emergence of new datasets of key ionospheric measurements with
global spatial and high-frequency temporal coverage, such as AMPERE (Active Magnetosphere and Planetary Electrodynamics
Response Experiment) magnetic field data measured onboard Iridium satellites. We are reporting first results for assimilationof low-altitude ionospheric measurements of magnetic field perturbations into a Lyon-Fedder-Mobarry (LFM) global magnetospheric model coupled with Rice-Convection Model (RCM).
We adopt optimal interpolation approach and rely on quasi-steady, linear approximation between equatorial magnetosphericpressure and field-aligned currents in the ionosphere. This approximation is estimated numerically by perturbing the LFM-RCM
model and by considering only large-scale modes from Fourier decomposition of the ionospheric magnetic field and equatorial
magnetospheric pressure.
The developed methodology was validated by using so called ”fraternal-twins” model-based assimilation tests. The numerical
LFM-RCM model with one set of parameters is used to generate synthetic observations, while model with differing set of parameters is used for assimilation and to calculate magnetospheric pressure corrections to be applied in order to reproduce synthetic
observations.
Keywords: data assimilation, ionosphere, MHD, magnetosphere

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PEM08-09

Room:302

Time:May 26 16:50-17:05

Impulsive enhancements of oxygen ions in the inner magnetosphere: Van Allen Probes
RBSPICE observations
KEIKA, Kunihiro1∗ ; SEKI, Kanako1 ; NOSE, Masahito2 ; MACHIDA, Shinobu1 ; LANZEROTTI, Louis J.3 ;MITCHELL, Donald G.4 ; GKIOULIDOU, Matina4 ; UKHORSKIY, Aleksandir4
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 World Data Center for Geomagnetism, Kyoto University, 3 New
Jersey Institute of Technology, 4 Applied Physics Laboratory, Johns Hopkins University
We investigate enhancements of O+ ions in the inner magnetosphere (L<6) during magnetic storms. Previous in-situ andremote-sensing observations by several investigators have confirmed that the O+ pressure increases on a substorm time scale(<10 min) rather than on a storm time scale (>hours). Such temporally impulsive enhancements can be caused by adiabatic,
impulsive transport and/or non-adiabatic acceleration. The relative significance of these two processes, however, remains an open
question and might even vary from event to event. We perform a case study of the 6 June 2013 storm, during the main phase ofwhich the RBSPICE instrument onboard the Van Allen Probes spacecraft observed short time-scale (<10 min) enhancements ofenergetic (>50 keV) proton and oxygen ion fluxes.
The ion injection event occurred at ∼2000 UT in the course of the main phase which started at about 16 UT. The Van Allen
Probes A and B were located at (X, Y, Z)SM = (-5.4, 1.5, 0.6)RE and (X, Y, Z)SM = (-5.3, 2.1, 0.7) RE, respectively. The flux
enhancements display only small energy dispersion, indicating that the westward edge of the injection region was close to thespacecraft but at a later MLT. The duration of the flux enhancements differ between the two spacecraft; the flux at ∼100 keV
continued for ∼5 min and ∼10 min at spacecraft A and B, respectively. The difference in the end time of the flux enhancements
enables us to estimate the ion drift speed to be ∼0.4 RE/min, suggesting that the eastward edge of the injection region was <1
RE eastward of spacecraft A. We thus estimate the spatial scale of the injection region to be <1 RE in the MLT direction. We
also compare energy spectra (phase space density vs. mu, the first adiabatic invariant) to identify whether ion acceleration isadiabatic or not. The energy spectral slope for both ion species did not change during the injection event. The oxygen spectra
were also shifted toward higher PSD by a factor of ∼3.
The results suggest that both ion species were accelerated adiabatically and that oxygen ions increased in density. We conclude
that, for this storm event, energetic (ring current) oxygen ions in the inner magnetosphere were enhanced by adiabatic, fasttransport of oxygen-rich plasma sheet plasma and/or adiabatic heating of preexisting cold/warm oxygen ions due to temporally
impulsive, spatially localized electric field fluctuations.
Keywords: ring current, oxygen ions, injections in the inner magnetosphere, magnetic storm and substorms, Van Allen probes
RBSPICE

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PEM08-10

Room:302

Time:May 26 17:05-17:20

One-year statistical analysis of ELF/VLF emissions at subauroral latitudes at Athabasca,
CanadaMARTINEZ CALDERON, Claudia1∗ ; SHIOKAWA, Kazuo1 ; MIYOSHI, Yoshizumi1 ; OZAKI, Mitsunori2 ;SCHOFIELD, Ian3 ; CONNORS, Martin3
1

Nagoya University, 2 Kanazawa University, 3 Athabasca University, Canada

Whistler mode waves in the ELF and VLF frequency range are naturally observed in the Earth’s magnetosphere. They are
generated around the equatorial plane and then propagate into the ionosphere along the field lines and can sometimes be detectedon the ground. Whistler mode waves play an important role for both generation and loss of energetic electrons in the innermagnetosphere. Especially, chorus waves outside the plasmapause cause non-adiabatic accelerations of MeV electrons of theouter belt, while plasmaspheric hiss contributes to the formation of the slot region through the pitch angle scattering. Additionally,
quasi-periodic (QP) emissions have also been associated with electron precipitation.
Using a 100 kHz-sampling loop antenna, we have continuously monitored ELF/VLF emissions at subauroral latitudes inAthabasca, Canada (MLAT=61.31, L=4.3) since September 2012. Using the data from 1 November 2012 to 31 October 2013, wehave made the first statistical analysis of ELF/VLF emissions at subauroral latitudes, taking into account their spectral features,
occurrence rates, and correlations with solar wind and magnetic variations.
We found that the occurrence is maximum in the morning sector (∼07 MLT) and minimum in the night sector (after 18 MLT)
with no particular dependence on seasons or AE and Dst indices. Chorus and hiss show a maximum occurrence rate at 07-08
MLT, while the highest occurrence of QP emissions is found around noon MLT. Even though these results show similarities withsatellite measurements in the inner magnetosphere, the occurrence rates obtained in this study show that the rates at ATH can be
up to 7 times lower than those in the magnetosphere. This suggests that not all waves that are generated in the magnetosphere canbe detected on the ground. Additionally, a superposed epoch analysis shows that AE index and solar wind speed slowly increases
up to several days before we start seeing the emissions in ATH. These results suggest that substorm activities associated withsolar wind high-speed streams can contribute to the generation of ELF/VLF waves that are detected at subauroral latitudes.

Keywords: ELF/VLF, statistics, subauroral latitudes, chorus, hiss, qp

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PEM08-11

Room:302

Time:May 26 17:20-17:35

Mechanics of magnetic storms and particles in the inner magnetosphere
EBIHARA, Yusuke1∗ ; TANAKA, Takashi2 ; FOK, Mei-ching3
1

RISH, Kyoto University, 2 Kyushu University, 3 NASA GSFC

Magnetic storms are known to occur when the southward component of the interplanetary magnetic field (IMF) lasts for a few
hours and more. The most common manifestation of magnetic storms is the development of the ring current. The convection
electric field plays an essential role in transporting the seed ions from the near-earth plasma sheet to the ring current. Relativistic
electrons, however, show a different behavior. In some cases, the differential flux of relativistic electrons decreases during thestorm main phase, and recovers during the storm recovery phase. Sometimes, the flux exceeds the pre-storm level. The rebuildof the radiation belt is thought to result from two different ways; one is non-adiabatic acceleration of electrons from the keVrange to the MeV range. The other one is adiabatic transport of relativistic electrons from the near-earth plasma into the radiation
belt. For both cases, transport of particles is a key in understanding the particle environment in the inner magnetosphere. By
performing the global magnetohydrodynamics (MHD) simulation and the bounce-averaged particle transport simulation, we havefocused on the following 3 unsolved processes regarding particles trapped in the inner magnetosphere in terms of mechanics ofthe magnetosphere. 1) First, we need to understand the origin of the convection electric field that is responsible for the transportof keV particles. The MHD simulation result shows that no steady convection electric field appears even though IMF is steady.
The contribution from the ionosphere is significant in the inner magnetosphere, and that associated with the MHD process is
significant in the near-Earth plasma sheet. 2) Secondly, we need to evaluate the influence of substorms on the transport ofparticles. If the dipolarization is governed by the MHD processes, it will progress in accordance with overall force balance inthe magnetosphere, so that the storm-time substorm will be different from an isolated substorm. 3) Thirdly, we need to grasp theparticle distribution function in the near-earth plasma sheet because most of them are the direct/indirect source of the ring current
and the radiation belt. According to the MHD simulation, the plasma sheet temperature becomes hot when the IMF is steadily
southward. The temperature exceeds 20 keV after elapsed time of several hours from the beginning of the southward turning of
IMF. The particle transport simulation predicts that the extremely hot plasma sheet gives rise to the enhancement of relativistic
electrons in the radiation belt.
Keywords: Magnetic storm, MHD simulation, Inner magnetosphere, Substorm, Convection electric field

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PEM08-12

Room:302

Time:May 27 09:00-09:15

The ERG project: current progress and the mission strategy
MIYOSHI, Yoshizumi1∗ ; SHINOHARA, Iku2 ; TAKASHIMA, Takeshi2 ; ASAMURA, Kazushi2 ;HIRAHARA, Masafumi1 ; MATSUMOTO, Haruhisa2 ; HIGASHIO, Nana2 ; KASAHARA, Satoshi2 ;MITANI, Takefumi2 ; YOKOTA, Shoichiro2 ; KAZAMA, Yoichi5 ; KASABA, Yasumasa3 ; MATSUOKA, Ayako3 ;KOJIMA, Hirotsugu4 ; KASAHARA, Yoshiya6 ; FUJIMOTO, Masaki2 ; SHIOKAWA, Kazuo1 ; SEKI, Kanako1 ;HORI, Tomoaki1 ; MIYASHITA, Yukinaga1 ; KEIKA, Kunihiro1 ; SHOJI, Masafumi1 ; OMURA, Yoshiharu4 ;EBIHARA, Yusuke4 ; NOSE, Masahito4 ; KATOH, Yuto2 ; ONO, Takayuki2
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 JAXA, 3 Tohoku University, 4 Kyoto University, 5 National Cheng
Kung University, Taiwan, 6 Kanazawa University
The ERG (Exploration of energization and Radiation in Geospace) is Japanese geospace exploration project. The projectfocuses on relativistic electron acceleration mechanism of the outer belt in the context of the cross-energy coupling via waveparticle interactions. The ERG satellite will be launched in FY2016. In this presentation, we report the current progress of the
ERG project including the development of the flight model of the satellite. Moreover, we present the strategy for the observations.
Since the geospace phenomena strongly depend on the local time and L-shell, we have a plan for the campaign observations that
focus on the specific phenomena. Possible coordinated observations with other geospace satellites and ground-based observations are also discussed.
Keywords: ERG project, international collaborations

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PEM08-13

Room:302

Time:May 27 09:15-09:30

Nonlinear wave growth theory of coherent hiss emissions in the plasmasphere
OMURA, Yoshiharu1∗ ; NAKAMURA, Satoko2 ; SUMMERS, Danny3 ; HIKISHIMA, Mitsuru4 ; KLETZING, Craig5
1

Research Institute for Sustainable Humanosphere, Kyoto University, 2 GraduateSchool of Science, Kyoto University, 3 Memorial
university of Newfoundland, 4 Solar-Terrestrial Environment Laboratory, Nagoya University, 5 Department of Physics and Astronomy, University of Iowa
Recent observations of plasmaspheric hiss emissions by the Van Allen Probes show that broadband hiss emissions in the plasmasphere comprise short-time coherent elements with rising and falling tone frequencies [1]. Based on nonlinear wave growththeory of whistler-mode chorus emissions [2], we examined the applicability of nonlinear theory to the coherent hiss emissions.
We have generalized the derivation of optimum wave amplitudes for triggering rising tone chorus emissions for both falling andrising tone hiss elements. The amplitude profiles of the hiss emissions are well approximated by the optimum wave amplitudes
for triggering rising or falling tones. Through formation of electron holes for rising tones and electron hills for falling tones, thecoherent waves grow up to the optimum amplitudes. We find an excellent agreement between the optimum amplitudes and theobserved amplitudes as a function of instantaneous frequency. We calculate nonlinear growth rates at the equator, and find that
nonlinear growth rates for rising-tone emissions are much larger than the linear growth rates. The frequency sweep rates and timescales of observed hiss emissions also agree those predicted by the nonlinear theory. Based on the theory, we can infer propertiesof energetic electrons generating hiss emissions in the equatorial region of the plasmasphere.
[1] Summers, D., Y. Omura, S. Nakamura, and C. A. Kletzing (2014), Fine structure of plasmaspheric hiss, J. Geophys. Res.
Space Physics, 119, 9134?9149,
doi:10.1002/2014JA020437.
[2] Omura Y., D. Nunn, and D. Summers (2012), Generation processes of whistler-mode chorus emissions: Current status of nonlinear wave growth theory, AGU Monograph ”Dynamics of the Earth’s Radiation Belts and Inner Magnetosphere”,
10.1029/2012GM001347.

Keywords: plasmasphere, wave-particle interaction, hiss, chorus, nonlinear wave growth, radiation belt

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PEM08-14

Room:302

Time:May 27 09:30-09:45

Relativistic radiation belt electron precipitation induced by EMIC triggered emissions in
the plasmasphere
KUBOTA, Yuko1∗ ; OMURA, Yoshiharu1 ; SUMMERS, Danny2
1

Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan, 2 Department of Mathematics and Statistics,
Memorial University of Newfoundland, St. John’s, Canada
Electromagnetic ion cyclotron (EMIC) triggered emissions have been observed by Pickett et al. [2010]. EMIC triggeredemissions are characterized by large wave amplitudes, rising-tone frequencies, and coherent left-hand circularly polarizedwaves. EMIC triggered emissions are generated by energetic protons with a temperature anisotropy. A nonlinear wave growththeory proposed by Omura et al. [2010] can explain the generation and growth mechanisms of EMIC triggered emissions.
Shoji and Omura [2011] have reproduced EMIC triggered emissions by hybrid simulations in agreement with the nonlinear
wave growth theory. The wave potential generated by coherent EMIC triggered emissions can trap some of electrons and guidethem down to lower pitch angles efficiently [Omura and Zhao, 2012]. Repeated interactions occur due to the mirror motion, andresult in the scattering of particles into the loss cone. Test particle simulations of electrons interacting with EMIC triggered emissions with a variable frequency and constant amplitude have been performed and the results show efficient electron precipitationinduced by the wave trapping in a parabolic magnetic field [Omura and Zhao, 2013]. From recent observations by THEMIS,
it is found that some EMIC triggered emissions have sub-packet structures [Nakamura et al., 2014]. We perform test particle
simulations of relativistic electrons interacting with EMIC triggered emissions which form sub-packets in a dipole magnetic field.
We include the convective growth of the waves in setting up the EMIC wave model for test particle simulations [Omura et al.,2010; Shoji and Omura, 2013]. By utilizing a three dimensional dipole magnetic field, we can trace electrons drifting in thelongitudinal direction. We study trajectories of longitudinally distributed relativistic radiation belt electrons drifting eastward
interacting with local EMIC triggered emissions. We obtain the relativistic electron distribution in equatorial pitch angle and in
pitch angle at the atmosphere.
Nakamura, S., Y. Omura, S. Machida, M. Shoji, M. Nose, and V. Angelopoulos (2014), Electromagnetic ion cyclotron rising
tone emissions observed by THEMIS probes outside the plasmapause, J. Geophys. Res. Space Physics, 119 , 1874–1886, doi:
10.1002/2013JA019146.
Omura, Y., J. Pickett, B. Grison, O. Santolik, I. Dandouras,M. Engebretson, P. M. E. Decreau, and A. Masson (2010), Theory
and observation of electromagnetic ion cyclotron triggered emissions in the magnetosphere, J. Geophys. Res., 115 , A07234,
doi:10.1029/2010JA015300.
Omura, Y., and Q. Zhao (2012), Nonlinear pitch angle scattering of relativistic electrons by EMIC waves in the innermagnetosphere, J. Geophys. Res., 117 , A08227, doi:10.1029/2012JA017943.
Omura, Y., and Q. Zhao (2013), Relativistic electron microbursts due to nonlinear pitch angle scattering by EMIC triggeredemissions, J. Geophys. Res., 118, 5008–5020, doi: 10.1002/jgra.50477.
Pickett J. S., et al., (2010), Cluster observations of EMIC triggered emissions in association with Pc1 waves near Earth’s
plasmapause, Geophys. Res. Lett., 37 , L09104 doi:10.1029/2010GL042648.

Shoji, M., and Y. Omura (2011), Simulation of electromagnetic ion cyclotron triggered emissions in the Earth’s inner magnetosphere, J. Ge
A05212, doi: 10.1029/2010JA016351.
Shoji, M., and Y. Omura (2013), Triggering process of electromagnetic ion cyclotron rising tone emissions in the inner magnetosphere, J. Geophys. Res., 118, 5553–5561, doi:10.1002/jgra.50523.

Keywords: relativistic electron, radiation belt, EMIC, EMIC triggered emission, precipitation, pitch angle

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PEM08-15

Room:302

Time:May 27 09:45-10:00

Statistical analysis of plasmaspheric EMIC waves
KATO, Yuichi1 ; MIYOSHI, Yoshizumi1∗ ; SAKAGUCHI, Kaori2 ; KASAHARA, Yoshiya3 ; MATSUDA, Shoya3 ;KEIKA, Kunihiro1 ; SHOJI, Masafumi1 ; KITAMURA, Naritoshi1 ; HASEGAWA, Shuhei1 ; KUMAMOTO, Atsushi4 ;SHIOKAWA, Kazuo1
1

Solar-Terrestrial Environment Laboratory, Nagoya University, Japan, 2 National Institute of Information and Communications
Technology, 3 Information Media Center, Kanazawa University, Japan, 4 Department of Geophysics, Graduate School of Science,
Tohoku University
We investigate statistically the plasmaspheric EMIC wave using the Akebono/VLF measurements. The plasmaspheric EMIC
waves are mainly observed at lower L-shell region (L<2). There are no significant MLT dependences and geomagnetic activities,
which are different from the EMIC waves outside the plasmapause. We also investigate statistically the magnetosonic mode
waves (MSW), and MSW are typically observed at L>2.5. There are some events to show that EMIC waves and MSW are
simultaneous observed, suggesting that MSW convert to EMIC waves inside the plasmasphere. Considering the results from thestatistical survey, we propose two different mechanisms on the origin of the plasmaspheric EMIC waves. One possibility is thecyclotron resonance with energetic ions. The estimated resonance energy of ions is a few hundred keV that are radiation belt
ions. Another possibility is the mode conversion from MSW. MSW propagate radially into the inner magnetosphere after thegeneration at the outer portion of the plasmasphere, and then MSW convert to EMIC waves.
Keywords: EMIC wave, statistical analysis, occurrence mechanism, magnetosonic wave, spatial distribution

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PEM08-16

Room:302

Time:May 27 10:00-10:15

A study of the Pc1 pearl structure using conjugate ground-satellite observations
JUN, Chae-woo1∗ ; SHIOKAWA, Kazuo1 ; TAKAHASHI, Kazue2 ; PAULSON, K.4 ; CONNORS, Martin4 ;SCHOFIELD, I.4 ; PODDELSKY, I.5 ; SHEVTSOV, B.5 ; KLETZING, C.6 ; WYGANT, J.7
1

Solar-Terrestrial Environment Laboratory, Nagoya University, 2 Space Physics Group (SRP), Johns Hopkins University Applied
Physics Laboratory, USA, 3 Space Science Center , University of New Hampshire, Durham, NH, USA, 4 Center for Science,
Athabasca University, Athabasca, Canada, 5 Institute of Cosmophysical Research and Radiowave Propagation, Russian Federation, 6 Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA, 7 of Physics and Astronomy, Universityof Minnesota, Minneapolis, Minnesota, USA
We have investigated the generation mechanism of the pearl structure of Pc1 geomagnetic pulsations using conjugate observations of an event with the ground induction magnetometers located at Athabasca (ATH, L = 4.3) in Canada and Magadan (MGD,
L = 2.7) in Russia and the Van Allen Probes (RBSP) A and B satellites located in the inner magnetosphere. The event wasobserved at ATH and MGD from 1500 to 1700 UT on October 6, 2012. During this event, the footprints of RBSP-A and -B werelocated near ATH and MGD, respectively. However, EMIC waves having frequencies close to that of the ground Pc1 waves weredetected only at RBSP-B, from 1632 to 1640 UT as it crossed the L=4 magnetic shell in the morning sector. On the ground, thePc1 waves exhibited a classical pearl structure with a repetition period of about 15 s. At both stations, the polarization angle
exhibited a large standard deviation, and a cross correlation analysis using the upper envelops of the wave amplitude reveals
that the correlation coefficient between the two stations is higher than 0.7 10 % of the time. The EMIC waves at RBSP-B also
exhibited a periodic variation in amplitude, but its period (about 5 s) differed significantly from that observed on the ground. The
direction of the Poynting vector parallel to the magnetic field alternated between northward and southward. This result indicatesthat bouncing wave packet can generate a Pc1 pearl structure in the magnetosphere. We suggest that Pc1 pearl structures can begenerated in the magnetosphere in the early stage but the beating of waves propagating in the ionospheric duct is responsible forthe peal structure observed on the ground.
Keywords: Pc1 pearl structures, Pc1 pulsations, EMIC waves, Multi-Point observations at the ground and space

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PEM08-17

Room:302

Time:May 27 10:15-10:30

Isolated proton auroras and Pc1/EMIC waves at subauroral latitudes
SAKAGUCHI, Kaori1∗ ; SHIOKAWA, Kazuo2 ; MIYOSHI, Yoshizumi2 ; CONNORS, Martin3
1

National Institute of Information and Communications Technology, 2 Solar-Terrestrial Environment Laboratory, Nagoya University, 3 Athabasca University
Isolated proton aurora (IPA) in the subauroral ionosphere is created by energetic proton precipitation through wave-particle
interactions with electromagnetic ion cyclotron (EMIC) waves in the conjugate inner magnetosphere. In this study, spatial distribution and occurrence probability of IPAs were statistically investigated as a proxy for regions of EMIC wave occurrence using
ground-based imaging data in 2006-2012 at Athabasca, Canada. The seven-year average of the IPA occurrence probability over
the total observation interval was estimated to be 0.83% and a factor of five change was found between maximum and minimum
years. Local time (between 16 and 06 MLT) distribution shows double peaks at pre-midnight and at dusk. The occurrence
probability increases with Kp and the MLT location tends to shift duskward. The statistical distribution of IPA size shows a clear
peak at a spatial size of 10,000 km2 , and latitudinal and longitudinal lengths have peaks at 56 and 340 km, respectively, at theionospheric altitude. The equatorial projections of IPA source locations and two-dimensional structures are estimated by magnetic field tracing. These spatial structures are essential to quantitatively estimate the loss rate of energetic particles, contributing
to space weather studies.
Keywords: proton aurora, EMIC wave, Pc1 pulsation, subauroral latitude, ring current proton, wave-particle interaction

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PEM08-18

Room:302

Time:May 27 10:30-10:45

Fine structure of plasmaspheric hiss
SUMMERS, Danny1∗ ; OMURA, Yoshiharu2 ; NAKAMURA, Satoko3 ; KLETZING, Craig A.4
1

Memorial University of Nfld,Canada, 2 Kyoto University,Japan, 3 Kyoto University,Japan, 4 University of Iowa,USA

Plasmaspheric hiss has been widely regarded as a broadband, structureless, incoherent emission. By examining burst-mode
vector waveform data from the EMFISIS instrument on the Van Allen Probes mission,we show that plasmaspheric hiss is acoherent emission with complex fine structure. Specifically, plasmaspheric hiss appears as discrete rising tone and falling tone
elements.
Our study comprises the analysis of two 1 hour samples,within which a total of eight 1 second samples were analyzed.
By means of waveform analysis on two samples,we identify typical amplitudes ,phase profiles, and sweep rates of the risingand falling tone elements. The new observations reported here can be expected to fuel a reexamination of the properties ofplasmaspheric hiss,including a further reanalysis of the generation mechanism for hiss.
Keywords: plasmaspheric hiss, Van Allen Probes, EMFISIS

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