資料6-H

Japanese URSI Commission H (Waves in Plasmas)
Activity Report
December 2014 - March 2015[1] Status of projects related with plasma wave observation
1.

The ERG project
http://ergsc.stelab.nagoya-u.ac.jp/index.shtml.en

2.

BepiColombo/MMO
http://www.stp.isas.jaxa.jp/mercury/p_mmo.html

3.

STEL VLF/ELF observations are carried out in Canada and Japan.
Details of the data are available at
http://stdb2.stelab.nagoya-u.ac.jp/vlf/index.html[2] Recent Meetings
1.

Meeting on Waves in Plasmas 2014, “New Developments in Plasma Wave Theory”,
Kyoto University, Uji, Kyoto, Japan, 5 December, 2014.
https://sites.google.com/site/sgepsshadou/koremade/meeting141205

2.

The Fifth Symposium on Polar Science, National Institute of Polar Research(NIPR), Tokyo, Japan, 2-5 December, 2014.
http://www.nipr.ac.jp/symposium2014/e/
The Fifth Symposium on Polar Science, National Institute of Polar Research3.

The 3rd Asia Oceania Space Weather Alliance (AOSWA) Workshop, The Luigans
Hotel, Fukuoka, Japan, 2-5 March, Japan.
http://aoswa.nict.go.jp/workshop_3/

4.

Joint Symposium on Heliosphere, Solar-Terrestrial Environment and Cosmic Ray
Modulation, Nagoya University, Nagoya, Japan, 4-6 March, 2015.

5.

Meeting on Acceleration and Transport of Particle and Turbulence caused by
Wave-Particle Interaction, Nagoya University, Nagoya, Japan, 5-6 March, 2015.

6.

ERG Science Meeting, Nagoya University, Nagoya, Japan, 13 March, 2015.
http://ergsc.stelab.nagoya-u.ac.jp/documents/science201503/

7.

Japanese URSI Commission H (Waves in Plasmas) Meeting, Nagoya University,
Nagoya, Japan, 13 March, 2015.

8.

Inner Magnetosphere Coupling III, UCLA, U.S.A., 23-27 March, 2015.
http://www.i-mp.org/conference/i-mp_2015/

資料6-H[3] Future Meetings
1.

ERG Mission Science Workshop, Taipei, 9-10 April, 2015.

2.

European Geosciences Union (EGU) General Assembly 2015, Vienna, Austria,
12-17 April, 2015.

3.

4th International Symposium on the Arctic Research (ISAR-4), Toyama, Japan,
27-30 April, 2015.

4.

Japan Geoscience Union Meeting 2015, Chiba, Japan, 24-28 April, 2015.

5.

42nd European Physical Society Conference on Plasma Physics, Lisbon, Portugal,
22-26 June, 2015.
A plenary talk titled “Generation mechanism of whistler-mode chorus emissions” will begiven by Y. Omura.

6.

The 26th General Assembly of the International Union of Geodesy and Geophysics(IUGG) , Prague, Czech Republic, 22 June - 2 July, 2015.
Sessions related to plasma waves:
A17 The Earth’s Plasmasphere: Remote Sensing and Modelling (Div. II-VERSIM)
A19 ULF Waves: Space-Ground Coordination (Div. III)
A20 ULF waves in the inner magnetosphere (Div. III)7.

The 12th International School/Symposium for Space Simulations (ISSS-12), Prague,
Czech Republic, July 3-10, 2015.

8.

Asia Oceania Geosciences Society (AOGS) 12th Annual Meeting, Singapore, 2-7
August, 2015.
Sessions related to plasma waves:
ST01 Energetic particle acceleration and transport in the geospace andinterplanetary space (Co-convener: Y. Miyoshi)
ST09 Sun-Earth system response to extreme solar and seismic events(Co-convener: Y. Omura)
ST12-31 Observation, theory and modeling of ULF, ELF and VLF waves in
geospace, and general session on magnetosphere (Main convener: M. Nosé,
Co-convener: Y. Katoh)
PS05 Solar wind interaction with planetary environments (Co-convener: Y.
Kasaba)[4] Recently Published Papers
1.

Kalaee, M. J., Y. Katoh, and T. Ono, Effects of the angle between the density
gradient and the external magnetic field on the linear mode conversion and資料6-H

resultant beaming angle of LO-mode radio emissions, Earth Moon Planets, 114,
1-15, doi:10.1007/s11038-014-9448-4, 2014.
Recent spacecraft's observations of kilometric continuum radiation showed that theobserved beaming angle of radiations often deviates from the prediction of thelinear mode conversion theory (LMCT). Satellite observations also show some local
fluctuation in the density gradient. Kalaee et al. [2014] considered the mode
conversion process from UHR- mode (slow Z- mode) to LO-mode (ordinary) waves,
focusing on the effect of the angle between the density gradient and the external
magnetic field on the efficiency of the LMCT and the resultant beaming angle ofconverted LO-mode waves; a comparison of the LMCT and simulation results arepresented. They first consider a condition that the density gradient isperpendicular to the external magnetic field, corresponding to the condition
assumed in the conventional LMCT. Next, they extend the discussion to thecondition that the density gradient is oblique to the external magnetic field. Theiraim is to investigate a condition where the efficient mode conversion can occur andto study the deviation of the beaming angle from that estimated by LMCT. From
the results of analyses, for both perpendicular and oblique cases, the highest
conversion efficiency is obtained for a certain value of the wave normal angle(critical wave normal angle) of the incident slow Z-mode waves, corresponding to
the case when two mode branches are matched. The simulation results show in theperpendicular case that the beaming angle is consistent with the conventional
LMCT; but in the oblique case a critical wave normal angle becomes different fromthe perpendicular case and the beaming angle is different from the LMCT
prediction.
2.

Kasahara, Y., Y. Goto, and Y. Oike, Automatic calibration method for analogue
wideband waveform receiver onboard the Akebono satellite, Journal of Space
Science Informatics Japan, 4, 41-49, 2015.
Akebono was launched in February, 1989 and has attained the 25 years ofsuccessful operation without major troubles. The VLF instrument onboard Akebono
measures plasma waves below 20 kHz and plays an important role to study plasma
physics in the Earth’s magnetosphere. The VLF measures not only wave spectrum
in digital format but also analogue waveform, and the analogue waveform data aretransmitted via analogue telemetry. Huge amount of analogue data have been
stored, but data analyses are not comprehensively performed so far because of the
difficulties of their peculiar characteristics. In the paper, current status of data

資料6-Hanalysis system developed for the VLF analogue waveform data and anticipatedoutcomes from these huge datasets are introduced.
3.

Koyanagi, J., A. Watanabe, N. Kawabata, T. Ozaki, K. Higuchi, K. Ishimura, and Y,
Kasaba, Long-term durability of tri-axial woven CFRP tube structure extended
along the spin axis of spinning platforms for the SCOPE mission, Adv. Composite
Materials, 23, 2, 115-128, doi:10.1080/09243046.2013.835921, 2014.
This study investigates the strength and long-term durability of a spin-axis
extensible rigid antenna element, made of tri-axial woven carbon fiber-reinforced
polymer (CFRP), for a spinning spacecraft. Due to a slight deviation between thespin axis and antenna-extended axis with the spin, the antenna is subjected tocentrifugal body force; the centrifugal force enhances the antenna deflection. A
relationship between centrifugal force and antenna deflection is derived from beam
theory. As the apparent material modulus decreases with time, the deflection
increases simultaneously. The time dependence of mechanical properties of thetri-axial woven CFRP is hence examined by a creep test. The time-dependent
failure criterion of the antenna is then examined using a flexural durability test.
Based on the beam theory and experimental results, they examine the long-term
reliability of applying the tri-axial woven CFRP to extensible rigid antenna for the
spinning spacecraft, especially for SCOPE mission; it is verified that the current
design tolerance for the mission assures certain durability for long-term usage.

4.

Martinez-Calderon, C., K. Shiokawa, Y. Miyoshi, M. Ozaki, I. Schofield and M.
Connors, Polarization analysis of VLF/ELF waves observed at subauroral latitudes
during the VLF-CHAIN campaign, Earth, Planets and Space, 67:21, doi:
10.1186/s40623-014-0178-7, 2015.
During the VLF Campaign observation with High-resolution Aurora Imaging
Network (VLF-CHAIN) from 17 to 25 February 2012, several types of VLF/ELF
emissions, including chorus, were observed at subauroral latitudes in Athabasca,
Canada. There has not been any comprehensive study of the physical properties ofsuch emissions at these latitudes. In this study, they calculate spectral andpolarization parameters of VLF/ELF waves with high temporal resolution. They
found that the polarization angle of several emissions depended on both frequency
and time. They suggest that the frequency-dependent events, which usually last
several tens of minutes, might be the consequence of the broadening of the ray paththat the waves follow from their generation region to the ground. Furthermore,資料6-H

time-dependent events, also lasting tens of minutes, have a polarization angle thatchanges from negative to positive values (or vice versa) every few minutes. Theysuggest that this could be due to variations of the wave duct, either near thegeneration region or along the wave propagation path. Using another groundstation in Fort Vermillion, Canada, about 450 km northwest of Athabasca, they
tracked the movements of the ionospheric exit point of three chorus emissions
observed simultaneously at both stations. Although they found that movement of
the ionospheric exit point does not follow a general direction, it is subject tohovering motion, suggesting that the exit point can be affected by small-scale
plasma processes.
5.

Matsuda, S., Y. Kasahara, and Y. Goto, M/Q = 2 Ion Distribution in the Inner
Magnetosphere Estimated from Ion Cyclotron Whistler Waves Observed by the
Akebono Satellite, J. Geophys. Res., doi:10.1002/2014JA020972, 2015. (accepted
manuscript online 11 March, 2015).
Matsuda et al.[2015] examined the spatial occurrence distributions of H+, He+, and
M/Q = 2 ion band ion cyclotron whistler waves observed by Akebono below analtitude of 10,500 km. These waves are categorized as electromagnetic ion cyclotron(EMIC) mode waves with characteristic spectrum properties that depend on the ioncomposition in the plasma. Statistical study is important for clarifying the variationof ion composition in a plasmaspheric ion environment. In this study, essential
differences were noted among the observed regions of each ion cyclotron whistler
wave band. The statistical analysis showed that the generation of H+ band ion
cyclotron whistlers in the equatorial region is difficult, while M/Q = 2 ion band ion
cyclotron whistlers are frequently observed near this region. A certain amount of
M/Q = 2 ions are evident. To explain these statistical results, they proposed a modelfor generation of several bands of ion cyclotron whistlers along a propagation path.
The magnetic local time dependence of the observed ion cyclotron whistlers was
also examined. The spatial occurrence distribution of the M/Q = 2 ion cyclotron
whistler waves is greatest inwards of L~2.4 in the local dayside; however, theyextend to L~3.0 in the local nightside. The results suggest a density enhancement
process of M/Q = 2 ions in the nightside plasmasphere, which is consistent withprevious satellite observations. This study presents important knowledge on theeffects of minor ion population on wave propagation and generation.

6.

Miyoshi, Y., S. Oyama, S. Saito, S. Kurita, H. Fujiwara, R. Kataoka, Y. Ebihara, C.

資料6-H

Kletzing, G. Reeves, O. Santolik, M. Clilverd, C. J. Rodger, E. Turunen, and F.
Tsuchiya, Energetic electron precipitation associated with pulsating aurora:
EISCAT

and

Van

Allen

Probe

observations,J.

Geophys.

Res.,

doi:10.1002/2014JA020690, 2015. (accepted manuscript online 16 March, 2015).
Pulsating auroras show quasi-periodic intensity modulations caused by theprecipitation of energetic electrons of the order of tens of keV. It is expected
theoretically that not only these electrons but also sub-relativistic/relativistic
electrons precipitate simultaneously into the ionosphere owing to whistler-mode
wave–particle interactions. The height-resolved electron density profile wasobserved with the European Incoherent Scatter (EISCAT) Tromsø VHF radar on 17
November 2012. Electron density enhancements were clearly identified at altitudes>68 km in association with the pulsating aurora, suggesting precipitation ofelectrons with a broadband energy range from ~10 keV up to at least 200 keV. The
riometer and network of subionospheric radio wave observations also showed theenergetic electron precipitations during this period. During this period, thefootprint of the Van Allen Probe-A satellite was very close to Tromsø and thesatellite observed rising tone emissions of the lower-band chorus (LBC) waves near
the equatorial plane. Considering the observed LBC waves and electrons, they
conducted a computer simulation of the wave–particle interactions. This showed
simultaneous precipitation of electrons at both tens of keV and a few hundred keV,which is consistent with the energy spectrum estimated by the inversion method
using the EISCAT observations. This result revealed that electrons with a wide
energy range simultaneously precipitate into the ionosphere in association with thepulsating aurora, providing the evidence that pulsating auroras are caused bywhistler chorus waves. It is suggested that scattering by propagating whistler
simultaneously causes both the precipitations of sub-relativistic electrons and thepulsating aurora.
7.

Nosé, M., S. Oimatsu, K. Keika, C. A. Kletzing, W. S. Kurth, S. De Pascuale, C.W.
Smith, R. J. MacDowall, S. Nakano, G. D. Reeves, H. E. Spence, and B. A. Larsen,
Formation of the oxygen torus in the innermagnetosphere: Van Allen Probes
observations, J. Geophys. Res., 120, 1182-1196, doi:10.1002/2014JA020593, 2015.
Nosé et al. [2015] studied the formation process of an oxygen torus during the 12-15
November 2012 magnetic storm, using the magnetic field and plasma wave dataobtained by Van Allen Probes. They estimate the local plasma mass density (ρL)
and the local electron number density (neL) from the resonant frequencies of資料6-Hstanding Alfven waves and the upper hybrid resonance band. The average ion mass(M) can be calculated by M~ρL/neL under the assumption of quasi-neutrality ofplasma. During the storm recovery phase, both Probe A and Probe B observe theoxygen torus at L=3.0-4.0 and L=3.7-4.5, respectively, on the morningside. The
oxygen torus has M=4.5-8 amu and extends around the plasmapause that is
identified at L~3.2-3.9. They find that during the initial phase, M is 4-7 amu
throughout the plasma trough and remains at ~1 amu in the plasmasphere,
implying that ionospheric O+ ions are supplied into the inner magnetospherealready in the initial phase of the magnetic storm. Numerical calculation under adecrease of the convection electric field reveals that some of thermal O+ ionsdistributed throughout the plasma trough are trapped within the expanded
plasmasphere, whereas some of them drift around the plasmapause on thedawnside. This creates the oxygen torus spreading near the plasmapause, which isconsistent with the Van Allen Probes observations. They conclude that the oxygen
torus identified in this study favors the formation scenario of supplying O+ in the
inner magnetosphere during the initial phase and subsequent drift during therecovery phase.
8.

Ozaki, M., S. Yagitani, K. Takahashi, T. Imachi, H. Koji, and R. Higashi, Equivalent
Circuit Model for the Electric Field Sensitivity of a Magnetic Search Coil of Space
Plasma, IEEE Sensors Journal, 13(3), 1680--1689, doi:10.1109/JSEN.2014.2365495,
2015.
An equivalent circuit model for the electric field sensitivity of an magnetic searchcoil (MSC) in a collisionless isotropic cold plasma is developed by Ozaki et al. MSCs
are sensitive to both magnetic and electric fields, but detecting electric fields is
unnecessary for magnetic observations of plasma waves. It is important to evaluate
both sensitivities for different geometries and electrostatic shields to avoid electricfield pickup. The electric field sensitivity is defined by a relationship between the
MSC impedance and the sheath capacitance. To confirm the validity of the circuit
model, the sensitivity to an electric field was measured by imposing an external
electric field using charged parallel metallic plates in laboratory experiments. The
coupling capacitance between the MSC and charged plates is equivalent to thesheath capacitance in a space plasma. The measured results showed good
agreement with an approximate expression deduced from the equivalent circuit
model. This agreement supports the validity of the proposed equivalent circuit
model. An electrostatic shield having slits is often used to reduce eddy current資料6-Hlosses in the shield. It has been found, however, that such slits result in a
deterioration of the electric field sensitivity by exposing a part of the sensor coil tothe plasma sheath. These results will be useful in evaluating the electric fieldsensitivity of an MSC covered by an electrostatic shield.
9.

Kasaba, Y., C. Tao, T. Kimura, M. Fujimoto, and W. M. Morooka, Planetary plasma
world: Magnetospheres of giant planets, J. Plasma Fusion Res., 90(12), 769‐774,
2014.

10. Saito, Y., H. Kojima, Y. Kasaba, T. Abe, S. Kasahara, and A. Matsuoka,
Observational technique of the solar system plasma: In-situ observation, J. Plasma
Fusion Res., 90(12), 780‐785, 2014.
11. Sato, Y., A. Kadokura, Y. Ogawa, A. Kumamoto, and Y. Katoh, Polarization
observations of 4fce auroral roar emissions, Geophys. Res. Lett., 42, 249-255,
doi:10.1002/2014GL062838, 2015.
Sato et al. [2015] reported on the first polarization measurement of auroral roaremissions near 4 times the ionospheric electron cyclotron frequency (4fce). A
ground-based passive receiver that uses orthogonal loop antennas, installed in
Iceland, revealed the sense of polarization of 11 events of 4fce roar emissions. In 9 of
11 cases, 4fce roar was left-handed elliptically polarized, namely, O-mode waves.
The O-mode 4fce roar was observed under both sunlit and dark ionosphericconditions during geomagnetic storms. For O-mode 4fce roar generation,satisfaction of the matching condition where upper hybrid frequency (fUH) equals
4fce requires a high-density, F region ionosphere, even during darkness, whichmight be attributed to auroral precipitation or tongue of ionization. In two cases,
right-handed elliptically polarized 4fce roar was observed during darkness hours
and the main phase of a geomagnetic storm. This polarization indicates that
nonlinear coupling of two upper hybrid waves may also work to generate X-mode
4fce roar.
12. Teramoto, M., N. Nishitani, V. Pilipenko, T. Ogawa, K. Shiokawa, T. Nagatsuma, A.
Yoshikawa, D. Baishev, and K. T. Murata, Pi2 pulsation simultaneously observed in
the E and F region ionosphere with the SuperDARN Hokkaido radar, J. Geophys.
Res. Space Physics, 119, 3444–3462, doi:10.1002/2012JA018585, 2014.
Teramoto et al. [2014] investigated Pi2 pulsations in the nightside ionosphere that

資料6-Hbegan at 14:15 UT (2315 LT) on 11 July 2010 observed with high-temporal (8 s)
resolution by beam 4 of the Super Dual Auroral Radar Network (SuperDARN)
Hokkaido radar. These pulsations were simultaneously observed in both theground/sea scatter echoes reflected from the F region height and in ionosphericechoes from field-aligned irregularities in the sporadic Es region. They had thesame period of 110 s and approximately no phase lag. From the radar observations
and the International Geomagnetic Reference Field model, the amplitude of theeastward (EEW) component of the electric field of the Pi2 pulsations in theionosphere was estimated ~8.0 mV/m in the F region and ~2.0 mV/m in the E region.
Corresponding Pi2 pulsations appeared dominantly in the horizontal northwardmagnetic field component (H) at nearby ground stations, Moshiri (MSR), St.
Paratunka (PTK), and Stecolny (STC), with amplitudes ranging from 6 nT (MSR) to
10 nT (STC). At the dominant frequency of 8.8 mHz, the coherences between H and
EEW were high (>0.9), the cross phases of EEW relative to H were −56 deg and −45
deg, and the amplitude ratios were 2.7 × 105 m/s and 8.4 × 105 m/s, in the E and F
regions, respectively. Based on a comparison of these results with theoreticalpredictions, they suggest that the concept of a pure cavity mode is not sufficient to
explain the combined observations for midlatitude Pi2 waves and that thecontribution of an Alfvén waves must be taken in account.
13. Tsugawa, Y., Y. Katoh, N. Terada, H. Tsunakawa, F. Takahashi, H. Shibuya, H.
Shimizu, M. Matsushima, Harmonics of whistler mode waves near the Moon, Earth
Planets Space, 67, 36, doi:10.1186/s40623-015-0203-5, 2015.
Tsugawa et al. [2015] investigated harmonic spectral features of electromagnetic
waves identified by Kaguya in the frequencies of several Hz around the Moon. The
waves have steepened waveforms peculiarly in the compressional component. The
fundamental waves have almost the same properties as narrowband whistler-mode
waves with the frequencies near 1 Hz, which have been observed around the Moon.
The waves are observed around the terminator region in the solar wind near the
lunar magnetic anomalies at the altitudes under 120 km. Tsugawa et al. suggestthat the harmonic spectra are a result of the nonlinear steepening of narrowband
whistler-mode waves. Although the narrowband whistler-mode waves have been
observed in the upstream region of many planetary bow shocks, such harmonics
have rarely been observed there. Since the harmonics are more frequently observed
at lower altitudes of the Moon, Tsugawa et al. [2015] suggested that these waves
are possibly caused by lunar intrinsic environments including lunar dusts and local

資料6-H

structures of lunar magnetic anomalies.
14. Yagi, D., Ken T. Murata, and Y. Kasahara, Evaluation of parallel distributed
processing of NICT science cloud for data analysis of waveform obtained by
spacecraft, Journal of Japan Society of Information and Knowledge, 25(1), (inpress), 2015.
Easy and effective parallel processing technique is required to analyze scientific big
data without heavy programming. Yagi et al. [2015] analyzed a set of waveform
data measured by the WFC-L receiver onboard “KAGUYA” for 9 months using their
original program. The practical issue is that it is not easy for many space scientists
to rewrite a program via parallelization library such as MPI (message passing
interface). In the present paper, they import their original program, without
rewriting, on a science cloud system on which a task manager is ready for use fordevelopment and management of parallel data processing. They demonstrated thateasy task scheduling and parallel processing is effective and practical for big data
analysis even in case that the data set is heterogeneous.