資料7-HJapanese URSI Commission H (Waves in Plasmas)
Activity Report
March 2014 - June 2014[1] Status of projects related with plasma wave observation
NICT Science Cloud
NICT Science Cloud has been developed for space plasma studies. We have begun todevelop a Web application for plasma wave data and other satellite observation data,
which is named “STARStouch”. This Web application is based on a technique ofasynchronous data transfer of graphic files for several types of data plots. The cloudsystem create a huge number of data plots with various time scale (e.g., from fewminutes to few years) for each data-set. Users can preview time-dependent
observation data of such multi-time scale plots with easy operations (tap, pinch, drag,flick…). Plasma wave (Figure 1), plasma particle, magnetic fields and orbit data of
the GEOTAIL satellite are available on the STARStouch GEOTAIL. We have opened
this Web site in May 2014.

Figure 1: STARStouch GEOTAIL version: http://geotail.nict.go.jp

資料7-H[2] Recent Meetings
1.

Japan Geoscience Union Meeting 2014, Yokohama, Japan, 28 April – 2 May, 2014.

2.

ISRSSP 2014 (Fourth International Symposium on Radio Systems and SpacePlasma) , Luxembourg, 26-27, June, 2014.

3.

AOGS 2014, Sapporo, Japan, 28 July – 1 August, 2014.

[3] Future Meetings
1.

The 40th COSPAR Scientific Assembly, Moscow, Russia, 2-10 August, 2014.

2.

The 31st URSI GASS, Beijin, China, 16-23 August, 2014.

3.

AGU Chapman Conference on "Low Frequency Waves in Space Plasmas", Jeju,Korea, 31 August - 5 September, 2014.

4.

Geospace revisited: a Cluster / MAARBLE / Van Allen Probes Conference, Rhodes,Greece, 15-20 September, 20145.

The 12th International Conference on Substorms, Ise, Japan, 10-14 November, 2014.

[4] Recently Published Papers (March 2014 – June 2014)1.

Toshihiro Habagishi, Satoshi Yagitani, and Yoshiharu Omura, Nonlinear damping ofchorus emissions at local half cyclotron frequencies observed by Geotail at L > 9, J. Geophys.
Res. Space Physics, Vol.119, pp.4475-4483, doi:10.1002/2013JA019696, May 2014.
A statistical analysis of upper band and lower band chorus emissions observed by the Geotail
spacecraft has been performed.

Chorus elements are generated near the magnetic equator (orthe high-latitude minimum-B pockets in the outer magnetosphere) as discrete emissions coveringa frequency range of 0.1-0.65 fce0, where fce0 is the cyclotron frequency in the generation region,
with wave vectors parallel to the ambient magnetic field.

As the emissions propagate away fromthe generation region, it is possible that they undergo the nonlinear damping at half the local
cyclotron frequency 0.5 fce because of the quasi-parallel propagation.

The nonlinear damping

can separate the emissions into the upper band and lower band chorus emissions.

It has beenfound that the lower cutoff of the upper band emissions coincides with 0.5 fce, while the upper
cutoff of the lower band emissions represents 0.5 fce0.

When 0.5 fce exceeds 0.65 fce0, thechorus emission is observed as a lower band-only emission.
2.

Satoshi Yagitani, Toshihiro Habagishi, and Yoshiharu Omura, Geotail observation ofupper-band and lower-band chorus elements in the outer magnetosphere, J. Geophys. Res.
Space Physics, Vol.119, pp.4694-4705, doi:10.1002/2013JA019678, June 2014.

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Using the Geotail observation of upper band and lower band (dual-band) rising tone chorus
waveforms in the dayside outer magnetosphere (L~10.5), it has been found that the lower cutoff
frequency of the upper band elements follows half the local gyrofrequency, whereas the upper
cutoff of the lower band elements is almost consistent with half the gyrofrequency at a minimumB pocket (a possible chorus generation region) according to the Tsyganenko geomagnetic model.
This is consistent with the scenario that the rising tone wave packet initially excited in a wide
frequency range suffers from damping at half the local gyrofrequencies during quasi-parallel
propagation.

Since the local gyrofrequency gradually increases away from the generation

region, the upper cutoff of a lower band element should represent half the gyrofrequency at thegeneration region, whereas the lower cutoff of an upper band element should follow half the local
gyrofrequency.

It has been confirmed that the frequency sweep rates and amplitudes of theobserved chorus wave packets are consistent with those predicted by the nonlinear growth theoryof chorus emissions, except for the frequency gap.
3.

S. Matsuda, Y. Kasahara, and Y. Goto, High-altitude M/Q=2 ion cyclotron whistlers in theinner magnetosphere observed by the Akebono Satellite, Geophys. Res. Lett., 41, 3759–3765,
doi:10.1002/2014GL060459, 2014.
An ion cyclotron whistler is a left-handed polarized electromagnetic ion cyclotron mode wave
converted from a lightning electron whistler. In the paper, M/Q = 2 ion cyclotron whistlers
observed by Akebono in the altitude region around 3200–10000 km (L = 1.5–3.4) was introduced.
The observation point was a considerably higher altitude than those previously reported, whichindicates that M/Q = 2 ions are present not only in the low-altitude region but also in the innermagnetosphere around L = 3.4. They also demonstrated that the concentration of M/Q = 2 ionsaround 4200 km (L = 1.7) during this event was plausibly up to 12.6%. This result gives important
clues to study unknown minor ion profiles such as circulation mechanism of deuterons orinjection mechanism of alpha particles in the solar wind.

4.

S. Matsuda, Y. Kasahara, and Y. Goto, Electromagnetic ion cyclotron waves suggesting
minor ion existence in the inner magnetosphere observed by the Akebono satellite, J.
Geophys. Res. Space Physics, 119, 4348–4357, doi:10.1002/2013JA019370, 2014.
EMIC waves in the vicinity of the geomagnetic equator exhibiting a sudden decrease in intensity(characteristic lower cutoff) at just above half of the proton cyclotron frequency were reported.
The waves were observed by Akebono along its trajectory during a magnetic storm in April 1989.
They demonstrated that the waves propagate with a large wave normal angle with respect to thegeomagnetic field line and that they had a crossover frequency above the characteristic lower

資料7-Hcutoff. The characteristic frequencies of each event did not vary despite disturbances in the innermagnetosphere, represented by a sudden decrease in the Dst index and electron density
fluctuation. In addition, the waves were repeatedly observed within a half day after sudden
decreases in Dst; however, they disappeared when the recovery of the Dst index became moderate.
Matsuda et al. suggested that wave generation appears to be closely correlated to fresh energetic
particle injection, and that the existence of a few percent of alpha particles (He++) or deuterons(D+) can explain the lower cutoff of the EMIC waves under the condition of multiple ion species.
5.

O. V. Agapitov, A. V. Artemyev, D. Mourenas, Y. Kasahara, and V. Krasnoselskikh, Inner
belt and slot region electron lifetimes and energization rates based on AKEBONO statistics
ofwhistler

waves,J.

Geophys.

Res.

SpacePhysics,

119,2876–2893,

doi:10.1002/2014JA019886, 2014.
Global statistics of the amplitude distributions of hiss, lightning-generated, and other whistler
mode waves from terrestrial VLF transmitters have been obtained from Akebono in the Earth's
plasmasphere and fitted as functions of L and latitude for two geomagnetic activity ranges (Kp<3and Kp>3). In particular, the present study focuses on the inner zone L∈[1.4,2] where reliable
in situ measurements were lacking. Based on this statistics, simplified models of each wave type
are presented, and quasi-linear pitch angle and energy diffusion rates of electrons by the full wave
model are calculated. Corresponding electron lifetimes compare well with decay rates of trappedenergetic electrons obtained from Solar Anomalous and Magnetospheric Particle Explorer andother satellites at L∈[1.4,2].
6.

Murata, K., Watanabe, H., Ukawa, K., Muranaga, K., Suzuki, Y., Isoda, F., Yamamoto, K.,
Kubota, Y., Nagatsuma, T., Sakaguchi, K., Tsugawa, T., Nishioka, M., Tatebe, O., Tanaka,
M., Fukazawa, K., Saita, S., Ebihara Y., Fujita, S., Kimura, E., Kurosawa, T., Murayama,Y., Nagai, T., and Mizuhara T. The NICT Science Cloud-A Proposal of Cloud System for
Scienti.c Researches-, Journal of Space Science Informatics Japan(ISSN 1349-1113),Vol.3(2014), pp.39-56, 2014.
This paper is to propose a cloud system for science, which has been developed at NICT (NationalInstitute of Information and Communications Technology), Japan. The NICT science cloud is an
open cloud system for scientists who are going to carry out their informatics studies for their own
science. The NICT science cloud is not for simple uses. Many functions are expected to thescience cloud; such as data standardization, data collection and crawling, large and distributed
data storage system, security and reliability, database and meta-database, data stewardship, longterm data preservation, data rescue and preservation, data mining, parallel processing, data
publication and provision, semantic web, 3D and 4D visualization, out-reach and in-reach, and資料7-H

capacity buildings.
7.

Murata, K., ISODA, F., Watanabe, H., Fukazawa, K., Yamamoto, K., Tatebe, O., Tanaka,M., and Kimura, E. High Performance Visualization Processing of Large-Scale Computer
Simulation Data via NICT Science Cloud, Journal of Space Science Informatics
Japan(ISSN 1349-1113), Vol.3(2014), pp.57-70, 2014.
Science cloud is a cloud system designed for scienti.c researches, and expected as a new
infrastructure for big data sciences. Not only parallelization of CPU as in super-computers, but
I/O and network throughput parallelization are crucial for the big data sciences. One of the typicalstructures of science cloud is a scalable cluster in which multiple clusters in a cloud are connectedwith high-speed network. In the present study, we examine performance of parallelization of both
CPU and I/O in a cloud system as the .rst step to high performance scalable clusters. In case withfew processes executed on each computational node (server), parallelization ef.ciency is almost
100%. This high ef.ciency is expected to maintain in larger-scale cluster systems such as thosewith 100 servers. On the condition of multi-processes on each node, the present parallelization
does not show good performance due to the congestions of I/O. Parallelization ef.ciency (speedup) is as low as 20.6%. New techniques of decentralization of I/O within each node are requiredin the next step.

8.

Kubota, Y., Murata, K. T., Yamamoto, K., Fukazawa, K. and Tsubouchi, K., Visualization
technique using a system of Magnetic Field Tracing in Global MHD simulations, Journal ofSpace Science Informatics Japan(ISSN 1349-1113), Vol.3(2014), pp.129-135, 2014.
We developed a system of Magnetic Field Tracing in Global MHD simulations in order tounderstand magnetosphere convection. To trace magnetic flux tube with high precision, we needto process big data such as all time-series simulation data. In this paper, we show a parallel
distribution visualization technique for magnetic field tracing by using NICT science cloud.

9.

Murata, K. T., Watanabe, H., Yamamoto, K., Kimura, E., Tanaka, M., Tatebe, O., Ukawa,K., Muranaga, K., Suzuki, Y. and Kojima, H., A high-speed data processing technique fortime-sequential satellite observation data, IEICE Communications Express, Vol.3(2014),
No.2, pp.74-79, 2014..
A variety of satellite missions are carried out every year. Most of the satellites yield big data, andhigh-performance data processing technologies are expected. We have been developing a cloudsystem (the NICT Science Cloud) for big data analyses of Earth and Space observations viaspacecraft. In the present study, we propose a new technique to process big data considering thefact that high-speed I/O (data file read and write) is important compared with data processing

資料7-Hspeed. We adopt a task scheduler, the Pwrake, for easy development and management of parallel
data processing. Using a set of long-time scientific satellite observation data (GEOTAIL satellite),
we examine the performance of the system on the NICT Science Cloud. We successfully archived
high-speed data processing more than 100 times faster than those on traditional data processingenvironments.
10. Shoji, M., and Y. Omura, Spectrum characteristics of electromagnetic ion cyclotron
triggered emissions and associated energetic proton dynamics, J. Geophys. Res. Space
Physics, 119, doi:10.1002/2013JA019695, 2014.
We perform parametric analyses of electromagnetic ion cyclotron (EMIC) triggered emissions
with a gradient of the nonuniform ambient magnetic field using a hybrid simulation. According
to nonlinear wave growth theory, as the gradient of the ambient magnetic field becomes larger,
the theoretical threshold of the wave amplitude becomes larger, although the optimum wave
amplitude for nonlinear wave growth does not change. With a larger magnetic field gradient, we
obtain coherent rising-tone spectra because the triggering process of the EMIC triggered emission
takes place only under a limited condition on the wave amplitude. On the other hand, with asmaller magnetic field gradient, triggering of the emissions can be caused with various wave
amplitudes, and then the subpackets are generated at various locations at the same time. The
concurrent triggering of emissions results in incoherent waves, observed as “broadband” EMICbursts.
11. Nakamura, S., Y. Omura, S. Machida, M. Shoji, M. Nosé, and V. Angelopoulos,
Electromagnetic ion cyclotron rising tone emissions observed by THEMIS probes outside
theplasmapause,J.

Geophys.

Res.

Space

Physics,

119,1874–1886,

doi:10.1002/2013JA019146, 2014.
We report observations of electromagnetic ion cyclotron (EMIC) triggered emissions observedby the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes
outside the plasmasphere. Although these phenomena have recently received much attentionbecause of the possibility of strong interaction with particles, only a few events of EMIC triggeredemissions have been reported near the equatorial plasmapause. We performed a survey of theTHEMIS probe data and found various types of emissions mainly on the dayside at radial
distances of 6–10 RE. We study three distinctive events in detail. The first is a typical event withan obvious rising tone emission in the afternoon sector. The emissions in the second event are
simultaneously excited in different frequency bands separated by the cyclotron frequency ofhelium ions. In the third event, which occurred near local noon, rising tone emissions wereexcited in an extended region near the equator where the field-aligned B gradient was much

資料7-H

reduced because of compression of the magnetosphere by the solar wind. We compare theseevents with the nonlinear wave growth theory developed by Omura et al. (2010). In all events, itis found that the observed relationship between the amplitudes and frequencies of the emissions
are in good agreement with the theory.
12. Y. Katoh, K. Iwai, Y. Nishimura, A. Kumamoto, H. Misawa, F. Tsuchiya, and T. Ono,Generation mechanism of the slowly drifting narrowband structure in the Type IV solar
radio bursts observed by AMATERAS, Astrophys. J., 787,45, doi:10.1088/0004637X/787/1/45, 2014.
We investigate the type IV burst event observed by AMATERAS on 2011 June 7, and reveal thatthe main component of the burst was emitted from the plasmoid eruption identified in the EUV
images of the Solar Dynamics Observatory (SDO)/AIA. We show that a slowly drifting
narrowband structure (SDNS) appeared in the burst’s spectra. Using statistical analysis, we revealthat the SDNS appeared for a duration of tens to hundreds of milliseconds and had a typicalbandwidth of 3MHz. To explain the mechanism generating the SDNS, we propose wave-wave
coupling between Langmuir waves and whistler-mode chorus emissions generated in a post-flareloop, which were inferred from the similarities in the plasma environments of a post-flare loop
and the equatorial region of Earth’s inner magnetosphere. We assume that a chorus element witha rising tone is generated at the top of a post-flare loop. Using the magnetic field and plasma
density models, we quantitatively estimate the expected duration of radio emissions generated
from coupling between Langmuir waves and chorus emissions during their propagation in the
post-flare loop, and we find that the observed duration and bandwidth properties of the SDNS areconsistently explained by the proposed generation mechanism. While observations in theterrestrial magnetosphere show that the chorus emissions are a group of large-amplitude wave
elements generated naturally and intermittently, the mechanism proposed in the present study canexplain both the intermittency and the frequency drift in the observed spectra.
13. 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., doi:
10.1002/2012JA018585, 2014
We investigated Pi2 pulsations in the nightside ionosphere that began at 14:15 UT (2315 LT) on
11 July 2010, and they were observed with high-temporal (8 s) resolution by beam 4 of theSuper Dual Auroral Radar Network (SuperDARN) Hokkaido radar. These pulsations weresimultaneously observed in both the ground/sea scatter echoes reflected from the F region
height and in ionospheric echoes from field-aligned irregularities in the sporadic Es region.

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They had the same period of 110 s and approximately no phase lag. From the radar observations
and the International Geomagnetic Reference Field model, the amplitude of the eastward (EEW)
component of the electric field of the Pi2 pulsations in the ionosphere 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 northward magnetic 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, thecoherences between H and EEW were high (>0.9), the cross phases of EEW relative to H were−56° and −45°, and the amplitude ratios were 2.7 × 105 m/s and 8.4 × 105 m/s, in the E and Fregions, respectively. Based on a comparison of these results with theoretical predictions, wesuggest that the concept of a pure cavity mode is not sufficient to explain the combined
observations for midlatitude Pi2 waves and that the contribution of an Alfvén waves must be
taken in account.