COMMISSION H : Waves in Plasmas (Nov. '2001 - Oct. '2004)
Edited by Toshimi Okada (okada@pu-toyama.ac.jp)
and Yoshiharu Omura (omura@rish.kyoto-u.ac.jp)

Based on the papers published from November of 2001 to October of 2004, we compiled
major achievements in the field of plasma waves and related studies made by Japanesescientists and their collaborators. We categorize the studies into two groups. One isbased on observations and experiments, and the other is theories and computer
simulations. Studies in each category are further divided into several sections. Eachsection provides a specific summary of important scientific achievements rather than acomprehensive report of the whole research activities of Japanese Commission H. On
the other hand, the reference list attached at the end is intended to be used as a
database of all papers we have collected from the Japanese Commission H members.

H1. Space Observation and Experiments of Plasma Waves
H1.1 Hydromagnetic and ULF Wave Phenomena
The four years covered by this report mark the start and growth of the ground-based remote-sensingof the magnetospheric plasma mass density by using ULF waves; from a geomagnetic field-line
eigen-frequency, that is identified by applying method(s) in a group of methods called "gradientmethods" to the data from two ground magnetometers separated in latitude by about 1 degree, one
can estimate the plasma mass density at the equatorial point along the field line that runs through the
midpoint of the two magnetometer sites.

By applying this procedure to a chain of groundmagnetometers, one can remote-sense the L-dependence of the magnetospheric equatorial plasma
mass density.

Kyushu University, Japan, having CPMN (Circum-pan Pacific Magnetometer

Network; previously called 210MM), has been working along this line of research. Kawano et al.
[2002] applied an improved method, called the "amplitude-phase gradient method" (APGM), to
actually observed data for the first time, and proved its usefulness; they further improved APGM sothat it can be applied to a chain of ground stations at once.

There exist papers on Pc pulsations: Matsuoka et al. [2002] studied high-latitude narrow-band Pc3
pulsations by using ground magnetometer arrays, SuperDARN radars, and the GEOTAIL satellite.
As a result they found that, at times, there existed high coherence between the pulsations in the dawn
magnetosheath and on the ground, from which fact they suggested that the driving source was
located in the magnetosheath.

Tanaka et al. [2004] statistically examined the longitudinal

structures of coherence, amplitude, and phase of the Pc-3 H component by using three longitudinallyseparated sub-equatorial stations, and reported for the first time a nearly in-phase structure in the0730-1700 LT sector and a nearly 180-deg phase jump across 0730 LT.

Motoba et al.

[2002;2003;2004] reported the existence of, and studied, Pc5-range magnetic-field oscillations on
the ground that were actually caused by oscillations of a DP2-type current system.
Electric and magnetic field variations inside the plasmasphere associated with suddencommencements (SCs) are analyzed based on the Akebono satellite observations. Shinbori et al.
[2004] showed that intense electric field disturbances with a bi-polar waveform associated with SCs
are followed by a dumping oscillation with a period of Pc3-4 ranges. The dumping oscillation
persisted for about 3-7 minutes in the equatorial region of the plasmasphere. The phase relation of
Ex and Bz components of the oscillation reveals that there is a phase lag of about 90 degrees withcompression nature. From this result, Shinbori et al. [2004] concluded that the dumping oscillation
generated by SC disturbances may be fast mode waves propagating in the plasmasphere.
Many scientists worked on Pi2 pulsations: Yamaguchi et al. [2002] presented a case study inwhich a bursty bulk flow (BBF) in the plasma sheet started prior to the corresponding ground Pi2
onset, but was preceded by th ecorresponding Pi2 onset at GOES8. From this and another feature
they suggested that the BBF was not the cause of the low-latitude Pi2. Shiokawa et al. [2002]
examined 10s-resolution ground-observed auroral images at the times of Pi2s, but did not find an
oscillation of the auroral luminosity synchronized with the oscillation of Pi2. Higuchi et al. [2002]
presented anew method to identify the Pi2 onset time; the method is based on statistical science anduses, e.g., Akaike Information Criterion (AIC).

Saka et al. [2002;2004] suggested, mainly based on

observations at the synchronous orbit, that impulsive dusk-to-dawn current near the nightside
synchronous orbit, which current is closed by field-aligned currents, is a source of Pi2.Nose et al.
[2003] investigated a morning-side Pi2 using ground stations andthe ETS-VI and EXOS-D satellites;from the dependence on (L,LT) of the observed waveform, period and phase, they concluded that thePi2 was caused by the plasmaspheric cavity mode resonance and that its longitudinal structure wasrather uniform.

Uozumi et al. [2004] investigated propagations of high-latitude Pi2s observed by

CPMN ground stations. With the aid of POLAR/UVI auroral images, they found that Pi2 wasobserved earlier (by about35s) in the polar cap than in the auroral region; thus, Pi2 in the polar capis
to be used to determine the substorm onset time.
hr.

They also found thestarting MLT of Pi2 to be 22.5

Fujitaetal.

(2001)

numericallycalculated

how

a

Pi2

pulsation

propagatesinmagnetosphere-ionosphere system. They also showed its relation with substorm current wedge(Fujita et al., 2002). In recent years, a cavity resonance mode has been widely believed as the main
mechanism of low-latitude Pi2 pulsations. Although it has been implicitly assumed that thefrequency should be the same throughout different local time zones for cavity resonance mode,
Kosaka et al (2002) and Han et al. (2003) found a local time dependence of dominant frequency.
To explain their results, Fujita and Itonaga (2003) made a numerical simulation and showed that thefrequency can be local time dependent in longitudinally non-uniform plasmasphere. The propagation
mechanism of Pi2 pulsations has also been investigated using satellite data by Nose et al. (2003) and
Han et al. (2004), and they confirmed that the cavity resonance mode is the most plausible
mechanism in low latitudes. The propagation characteristics in high-latitudes (Uozumi et al., 2004)
and in low-latitudes on dayside (Han et al., 2004) were also investigated.
As regards Sudden Commencements/Impulses (SC/SI), Takeuchi et al. [2002a]reported thatnegative SIs are not caused by reverse shocks but by varied structures such as tangential
discontinuities at high-low speed stream interaces, front boundaries of interplanetary magnetic
clouds, and trailing edges of heliospheric plasma sheets.

Takeuchi et al. [2002b] reported that, for

an SC with long rise time (30 min), the corresponding interplanetary shock, observed in the solar
wind, was as sharp as usual SCs, but its normalwas highly inclined duskward. Araki et al. [2004]
statistically analyzed SCs, and reported that the rise time is essentially determined by time for aninterplanetary shock to sweep geoeffective magnetopause length L, which they estimated to be about
30 Re.
Nakagawa et al. [2003] reported left-handed ULF waves with frequency of 0.3-1.1 Hz
detected by GEOTAIL at 27 lunar radii upstream of the moon when GEOTAIL was
located on field lines that ran through the lunar wake. They explained the observation
by polarization-reversal of right-handed, sunward-propagating electron whistler waves
with frequencies above 1.4 Hz in the solar wind rest frame, and suggested that thewaves were excited by electron beams that had field-aligned-flowed anti-sunward
through the lunar wake.
H1.2 Generation and Propagation of ELF/VLF Waves
The Geotail spacecraft has observed Lobe Trapped Continuum Radiation (LTCR) in the Earth's
distant magnetotail in the frequency range from several hundreds of Hz up to 8 kHz. Takano et al.
[2001, 2004] have estimated the generation region of the LTCR by means of direction finding and
3-d ray tracing analyses. The direction finding analysis with the wave form data of the LTCR has
shown that most of the LTCR propagates along the dawn-dusk direction. Comparing this result withthe 3-d ray tracing analysis, the generation region of the LTCR has been estimated to be locatedaround the plasma sheet boundary layer and the low latitude boundary layer of the distantmagnetotail.
The low latitude boundary layer (LLBL) is a region where solar wind momentum and energy istransferred to the magnetosphere. Enhanced “broadband”electric plasma waves from <5 Hz to 105
Hz and magnetic waves from <5 Hz to the electron cyclotron frequency are characteristic of the
LLBL. Tsurutani et al. [2003] reviewed wave-particle interactions, with focus on cross-diffusion
rates and the contributions of such interactions toward the formation of the boundary layer andpresented a scenario where the global solar wind-magnetosphere interaction is responsible for theauroral zone particle beams, the generation of plasma waves and the formation of the boundary
layer.
Shinbori et al. [2002] reported that plasma wave phenomena associated with suddencommencements (SCs) are analyzed by using the Akebono satellite observation data which havebeen carried out for more than 13 years since March 1989. The 719 cases of SC events showed anenhancement of plasma waves with one-to-one correspondence to the SC onsets measured at
Kakioka in the inner magnetosphere, plasmasphere, polar ionosphere. In the middle latitude and in
the equatorial region of plasmasphere, electromagnetic whistler, LHR, ion cyclotron mode waves are
generated, while in the high latitude region, clear enhancements of electrostatic whistler mode waves
with broad-banded spectra are observed.
From time difference between the onset times of SC on the ground and the plasma wave
enhancements, Shinbori et al. [2003b] verified that the propagation nature of the SC disturbances
deduced from these observations has shown two folding signatures; one route is crossing the equator
regions with an average speed of 389.5km/sec, and the other route is passing the polar regions
entering from the cusp region and propagating from dayside to nightside polar ionosphere with anaverage speed of 47km/sec.
Higashi et al. [2004] estimated the impedance of the wire dipole antennas onboard the Akebono
satellite by using the electromagnetic field observations for Omega navigational signals.

Theestimated capacitance and resistance exhibit specific spin variation, which would be caused by theplasma sheath formation around the antenna wires depending on the angle between the antenna
direction and the geomagnetic field line.
Imachi et al. [2004] studied the effective lengths of a wire dipole antenna onboard spacecraft andfound the frequency dependence from DC (static) to AC (wave) electric fields by a “rheometry”
experiment, where a scale model of the antenna is immersed in a water tank with two electrodes
creating a quasi-static electric field in it.
The SS-520-2 rocket experiment was carried out over Ny-alesund, Svalbard, Norway, on Dec. 4,
2000, in the dayside polar region. With the onboard Plasma Wave Analyzer (PWA), Ueda et al.

[2003] have observed impulsive packet-like waveforms with frequencies around 3 to 4 kHz as well
as auroral hiss emissions. The packet-like waveforms were linearly polarized, and appeared for theduration of 100-500 ms, with their spectral peaks well below the lower cutoff of the auroral hissemissions. The cross correlation obtained with the PWA interferometry system has estimated thephase velocity of the packet-like waves to be about 60 km/s. With the linear dispersion analysis they
have shown that the most plausible wave mode for the packet-like waveforms is the lower hybrid
wave excited by electron beams. On the other hand, the Electric Field Detector (EFD) onboard theSS-520-2 rocket was designed to observe DC electric fields and plasma waves with frequencies up
to 50 Hz. Miyake et al. [2003] have analyzed EFD data, especially on natural DC electric fields
observed in the noon polar region, by eliminating inductive electric fields with estimating several
parameters. They have shown that natural DC electric fields were observed around the apogee anddescending period of the rocket's trajectory, with their magnitudes of 20-40mV/m, and with almost
south-westward directions.
Two large scientific balloons (PPB: Polar Patrol Balloon) were launched on Jan. 13th, 2003 at
Syowa Station in the antarctica. The balloons reached the altitude of 33km, and observed importantscientific data for about two weeks. Miyake et al. [2004] have participated this project in observing
ELF/VLF electromagnetic waves. They developed a wide-band electromagnetic wave receiver
EMW (ElectroMagnetic Wave receiver) onboard PPB, which can observe waveforms of ELF waves
and power spectra of VLF waves. This EMW receiver worked properly, and succeeded to observe
clear electromagnetic wave data.

Singh and Hayakawa [2001, 2003] examined the relative merits of ducted and non-ducted
propagation of low-latitude whistler critically in the light of work done mostly in the Asian countries.
They found a growing consensus in favor of the non-ducted pro-longitudinal mode of propagation
for nighttime whistlers, and ducted propagation for daytime whistlers. Hayakawa and Ohta, [2003]
reviewed the direction finding systems and suggested the importance of the use of direction finding
in VLF studies with a few experimental examples.
In an attempt to monitor subsurface VLF electric field changes associated with earthquakes, aborehole antenna has been installed at Agra, India. Some preliminary data analysis by Singh et al.
[2003] has indicated penetration of ionospheric/magnetospheric VLF signals to large depths in thecrustal region and caution for careful identification of seismogenic VLF signals.
Hayakawa and Nickolaenko [2001] reviewed lightning effects onto the mesosphere and lower
ionosphere extensively in relation to the generation of sprites and elves and the associated ELF
transients. Hobara et al., [2001, 2003] and Hayakawa et al, [2004b] have carried out the observationof sprites for the winter lightning in the Hokuriku area of Japan and found that sprites are reallytriggered mainly by +CGs whose charge moment change is exceeding the threshold of 200~300

C·km.
Otsuyama et al. [2002, 2003a, 2004a, 2004b] studied the VLF signature of ionosphericperturbations (Trimpis) associated with winter lightning in the Hokuriku area. They found that there
is no significant difference in the Trimpi occurrence rate between –and + CGs. Otsuyama et al.
[2002] also performed the FDTD computer simulation for VLF scattering in the Earth-ionosphere
waveguide.
Molchanov et al. [2001] investigated the modulation in the amplitude and/or phase of
subionospheric VLF propagation. The result indicated the significant power in the frequency rangeof atmospheric gravity waves.
Hayakawa et al. [2004a] have presented the long-term observational results on the ionospheric
Alfven resonance at middle latitudes on the basis of observation at Kamchatka and introduced a lotof resonance properties. Nickolaenko et al. [2004c] suggested an alternative mechanism due to thewave interference in the ionosphere and magnetosphere.
Ando et al. [2002] have theoretically investigated the penetrations of power line harmonics andcompared with the previous satellite VLF observation.
Soloviev and Hayakawa [2002, 2004] have proposed an algorithm to study the VLF scatteringwith taken into account a 3D local ionospheric irregularity over the ground of the solar terminatortransition on the basis of a mathematical model, an asymptotic theory and an appropriate numericalmethod.
Hayakawa and Otsuyama [2002], Otsuyama et al. [2003b] and Otsuyama and Hayakawa[2004]
have applied the FDTD method to the global Schumann resonances. They demonstrated that thisapplication is expected to be very useful for the complicated ionospheric models (day/night
asymmetry, local ionospheric perturbation etc.).
Ando and Hayakawa [2004] have studied the inverse problem extensively for the Schumann
resonance data observed at a few stations in the world and deduced the global distribution of
background lightning activity.
Nickolaenko et al., [2004a, 2004b] have developed an algorithm to accelerate the convergence ofthe time domain formal solution for the natural ELF transient pulses in the Earth-ionosphere
waveguide.

H1.3 Electrostatic Waves Excited by Electrons
Electrostatic waves associated with reconnection phenomena in the dayside magnetosphere region,
were reported by Matsumoto et al. [2003] using the observation results by Geotail skimmed along
the dayside magnetopause. They confirmed the 3-dimensional multiple x-line magnetic
reconnections take place in the same time period. The observed electrostatic waves are Electrostatic

Solitary Waves (ESW) and Amplitude Modulated Electrostatic Waves (AMEW). They showed thatthe enhanced broadband electrostatic emissions associated with reconnection are not random noises
but are nonlinear coherent structures which may provide important dissipation in the electron
diffusion region during reconnection.
In the auroral zone and polar cap region outside the plasmapause, Shinbori et al. [2002, 2003b]
reported that electrostatic whistler mode waves with broad-banded spectra suddenly appear below
the local electron cyclotron frequency associated with SC onsets measured at Kakioka in the plasma
wave data of the Akebono satellite. The ratio (E/H) of electric and magnetic field intensity of theplasma waves at 17.8 kHz obtained by the VLF instruments onboard the Akebono satellite is muchlarger than that of electromagnetic waves in vacuum. This result suggested electrostatic nature of thewhistler mode waves. From simultaneous observation of low energy electrons by the
Akebono satellite, Shinbori et al. [2003b] showed that the electrostatic whistler mode waves are
excited by electron beams with an energy range of less than 100 eV.

H1.4 Electromagnetic Waves Excited by Electrons
Umeda et al. [2004] presented particle simulations of electrostatic solitary waves (ESW) observedby the Geotail spacecraft and recent spacecraft in the Earth's magnetosphere. Recent particle
simulations have demonstrated that ESW correspond to Bernstein-Greene-Kruskal electron holes
formed through nonlinear evolution of electron beam instabilities. Since an electron hole is acoherent electrostatic potential structure, electron beam instabilities were conventionally studied byelectrostatic particle simulations. However, the Polar spacecraft and FAST spacecraft observed
electromagnetic field signatures associated with ESW. To study interaction between coherent
electrostatic potentials and electromagnetic waves, we extend the previous electrostatic particle
model to an electromagnetic particle model. In the present two-dimensional simulations of anelectron beam instability, electromagnetic field components are enhanced around two-dimensional
electron holes. We found that the enhancement of electromagnetic fields is due to a current formedby electrons undergoing the E × B 0 drift, where the electric field is a perpendicular electrostatic fieldat the edge of a two-dimensional electron hole. An electromagnetic beam mode is excited by thecurrent due to the drifting electrons moving with the electron hole. The amplitude ratio of theelectric field to the magnetic field is estimated on the basis of the present simulation result, and it isin agreement with those of the Polar and FAST observations.
Imhof et al. [2004]

made comparisons between X-ray (>2 keV) emissions emanating from the

Earth's Northern Hemisphere aurora observed on the Polar satellite and auroral kilometric radiation(AKR) plasma wave intensities detected on the Geotail satellite. For this comparison the plasma
wave frequencies were divided into a low-frequency (LF-AKR) (30-100 kHz) band and ahigh-frequency (HF-AKR) (100-800 kHz) band. For the LF-AKR band the correlation coefficientswith auroral X-ray emissions are generally high intensities often display slower recovery times than
do the LF-AKR. and significantly larger than the corresponding coefficients between X-ray and
HF-AKR variations. It is found that short time-scale variations of the LF-AKR activity often
correspond to the temporal fine structure of the intensity (5-10 min) of X-ray auroral emissions.
HF-AKR intensity enhancements generally precede enhancements of the X-ray emissions, while the
LF-AKR intensity enhancements generally lag the X-ray enhancements. This sequence implies thatauroral acceleration begins at lower altitudes and then moves to higher altitudes. In addition, thetime profiles of the X-ray

A year's worth of observations of kilometric continuum (KC) from the plasma wave instrument(PWI) on GEOTAIL and extreme ultraviolet (EUV) images of the plasmasphere from IMAGE arecompared.

In the vast majority (94%) of the 87 cases when simultaneous data from both spacecraft

were available, KC was observed to be associated with density depletions or notch structures in theplasmasphere.

From a careful analysis of 1 month of EUV data comprising 13 notch structures,

only one notch structure was found in which no accompanying KC was observed when GEOTAIL
was in a low-latitude position and therefore should have observed the emission if it were generated.
IMAGE observations from the radio plasma imager (RPI) during passage through a plasmasphericnotch structure found that KC was generated in or very near the magnetic equator at steep gradientsin density and associated with emissions in the upper hybrid resonance band as previously reported
by others at lower frequencies. Statistical analysis of the KC events associated with plasmasphericnotch structures shows that the typical source region is at an equatorial radial distance of 2.4 RE(Earth radii) in the magnetic equator and produces an emission cone that is 40° in longitude and 20°
in latitude. These results show that a density depletion or notch structure in the plasmasphere istypically a critical condition for the generation of KC but that the notch structures do not always
provide the conditions necessary for the generation of the emission. (Green et al. [2004])
The propagation characteristics of auroral kilometric radiation (AKR), the propagation mode,
power flux as well as propagation direction, have been analyzed by applying the wave distributionfunction method to the Poynting flux measurement data of the Akebono satellite. Hosotani et al.
[2001] showed that the power flux of O-mode waves was about 10% of the X-mode wave intensity
in strong AKR emissions. The X-mode AKR waves tend to fill inside the radiation cone of an auroral
field line, while the O-mode AKR waves showed two different propagation directions: one was
directed to almost 90 degree with respect to the local magnetic field and the other showed the
propagation angle of about 40 degree. From the above results, Hosotani et al. [2001] concluded thatthe source locations of the O-mode AKR waves with the above propagation angle located close to
the source of the intense X-mode AKR waves.

Murata et al. [2004a] studied the Auroral kilometric radiation(AKR) occultations in the vicinity of
the Earth using two observations by GEOTAIL and POLAR. They compared the dynamic spectra ofboth satellites for eight months paying attention to times and frequencies at which AKR is observed
simultaneously. Then, we carefully examined the AKR illumination regions using the POLAR
two-month orbit data. Two distinct regions where the AKR is occulted are found during the period.
One is the region on the night side of the Earth, where the AKR does not propagate at frequencies >400kHz. The other region is in the vicinity of the plasmapause, on both the day and night side of the
Earth.
Long-term data analysis results of the seasonal variations of AKR activity by Kumamoto et al.
[2001] suggested that field-aligned potential drops varies depending on the seasons. The idea was
supported by Kumamoto et al. [2001], which clarified the similar seasonal variations of upflowingion (UFI) events. Furthermore, Kumamoto et al. [2003a] have discovered the solar cycle dependenceof vertical distribution of AKR sources and UFI events: AKR and UFI are quiet during solar
maximum while they become active during solar minimum. By Kumamoto et al. [2003b], long-term
variations of ambient plasma density in the auroral regions has been derived from whistler wave data,
and discussed as a control factor of solar cycle variations of field-aligned potential drops and AKR
sources.
Shinbori et al. [2003a] showed that the plasma wave data from 263 satellite passages covering the
SC onsets included 85 cases of AKR enhancement within a frequency range from 100 kHz to 1.2
MHz. The start time of the AKR enhancements tended to occur after the SC onsets determined byusing the geomagnetic records of the Kakioka Magnetic Observatory within a time range from 3 to 8
minutes. The averaged time is about 5.26 minutes. Based on the delay time feature, the magnetic
disturbances associated with SCs were thought to propagate from the dayside magnetosphere to thenightside tail region where they compressed the plasma sheet. Furthermore, Shinbori et al. [2003a]
discovered the 19 cases of the data sets indicating an enhancement of terrestrial hectometricradiation (THR) occur 1 to 9 minutes after the SC onsets, with the averaged time of 5.84 minutes.
The second harmonic wave properties of AKR were investigated by using the plasma wave data of
the Akebono satellite. The statistical analysis results by Hosotani et al. [2003] showed that theprobability of a harmonic event occurrence is more than 60% of all AKR events, whose relationshipbetween the frequencies of the fundamentals and the second harmonics is exactly two times for theupper and lower cut-off frequencies of the spectra as well as the fine structures. Hosotani et al.
[2003] showed that the intensity ratio of the second harmonics to the fundamentals exhibits a
two-fold nature, with both a linear and a quadratic relationship. Furthermore, the second harmonic
waves of the X-mode of AKR are generated from a source which is identical to that of fundamental
waves of the O-mode. These data analysis results suggest that possible generation mechanism of
AKR harmonic structure should allow the coexistence of different AKR emission processes.

H1.5 Observational and Experimental Techniques

In order to determine the propagation mode of Jovian decametric radiation (DAM), Nakajo et al.
[2001] instrumented the long range baseline interferometer and examined the stability of the phase
information to the interferometry system. In the long baseline interferometer observation, it has been
well known that the observed fringe phases are fluctuated by the temporary variation of TEC (Total
Electron Contents). The dual frequency interferometer method is a powerful method to eliminate theinfluence of TEC; however, the problem caused by the dependence of the linear equations must be
considered in the case of the observation of Jovian decametric radiation. Based on a simulation study,
Nakajo et al. [2001] also showed that the following conditions are required in order to solve thisproblem; that is (i) the fringe phases are detected with accuracy under the standard deviation of 6
degree, and (ii) the temporal variation of TEC difference between two observation sites should besmaller than 5.0x1015[1/m2].
S-burst phenomena of DAM are investigated by Oya et al. [2001a], who reported that dynamic
spectra of the S-bursts are obtained by using a high time resolution radio spectrograph with a time
resolution of 2 ms and a bandwidth of 2 MHz. Within the occurrence feature of 65 S-burst events
observed in the period from 1983 to 1999, 26 events have been identified as the S-N burst events,
which are characterized by the interaction between the S-burst emissions and the Narrow band
emissions.
Oya et al. [2001b] have developed array antenna system and multi-frequency interferometer
network to investigate the electromagnetic radiation process in the Jovian magnetosphere. To
understand the energy source and the radiation process of DAM with correlation to the Jovian
auroras, ionosphere-magnetosphere couplings and interactions with satellite Io, it is important toobtain the information on the source location and the polarization of DAMs. The array antenna
system consists of 9 antennas covering a frequency range from 20 MHz to 30 MHz. The new long
baseline interferometer system employs the multi-frequency interferometer method by which
ionosphere scintillation effect can be largely reduced.
Tsutsui (2002) developed a newly developed system for measuring electromagnetic (EM)environment in the earth, we detected earth-origin electric pulses which were leaking out of theground. The author reported that intensity of the electric pulses detected above the ground was
weaker than those in the earth. Due to the clear lower frequency cutoffs appeared in their spectra hesuggested the existence of a kind of horizontal wave-guide in the earth and the propagation of EM
waves there. The estimated scale depth of the bottom conductive boundary of the wave-guide isconsistent with the result obtained from geomagnetic field investigations.

In the dynamic spectra of the S-N burst, Oya et al. [2002] found the trend of emissions withnegative and slower frequency drift named as "Trailing Edge Emission (TEE)", which are often
observed shortly after the appearance of the S-burst. Detailed analyses of these phenomena revealed
that the TEE is not a manifestation of S-burst with slower drift rate but a variation of N-burst. The
results suggested that S-burst and the associated TEE are formed simultaneously started from acommon region with different drift rates. Furthermore, Oya et al. [2002] interpreted that theappearance of the S-bursts is not controlled by the geometrical effect between the source region andthe observer, but directly reflects the generation of the source region widely distributed in an altitude
range from a few thousands km to 30.000 km, along the Io flux tube.
Oya and Iizima [2003] proposed a new method for detecting the phase difference of cesium
frequency standards facilitated at coupling stations of an interferometer of 100km range baselines forobservations of decameter wavelength radio waves. In this method, the Earth's rotation is utilized.
That is, a time-depending variation of the phase differences of arriving radio waves from a given
source forms a so-called fringe function due to the Earth's rotation. The feasibility of the proposed
method has been verified by applying the method to observations of a 100km range baseline
interferometer for decameter wavelength radio waves at Tohoku University selecting the radio-wave
sources in the Cassiopeia A supernova remnant as the objective. The results of the analyzed
correlation values averaged for the observation data of 30hr, at 22.158MHz, are determined being
scattered around average values with a distribution of less than 25%; this distribution corresponds toa phase determination error of for the cesium frequency standards of the interferometer at 10MHz.
Hashimoto et al., (2003) developed a software wave receiver utilizing a programmable down
converter (HSP50214B) and a digital data processor (TMS320C31) to obtain the spectra andwaveform of plasma waves in wide frequency ranges of ELF, VLF and LF bands with highfrequency and time resolution. They reported the successful flight test by using the SS520-2 rocket
experiment on Dec. 2000 launched from Ny-Alesund in Svalbard in Norway. The result of the rocket
experiment provided the verification of digital receiver system on-board the SELENE spacecraft.
Hashimoto et al. [2003] developed a software wave receiver and was installed aboard theSS-520-2 rocket as a part of the Plasma Wave Analyzer (PWA). This receiver consists of a waveformreceiver using real-time data compression and a spectral receiver with high time and frequency
resolution using a Programmable Down Converter (PDC). They reported the first flight test of the
new plasma wave receiver to be used for future planet explorers and space observation missions.
Every 0.5 seconds, spectra of a 3MHz signal with 0.3kHz resolution are obtained and the datacompression of waveforms

with the bandwidth of 15 kHz are performed. Although the sweep time

was occassionally affected if the data were not compressed enough, no data were lost during theflight.

H2. Theory and Computer Experiments on Plasma Waves
H2.1 Wave Instabilities

Kasaba et al. [2004] studied several topics related to the 2fp radiation generated in the terrestrial
electron foreshock. Our investigation started from the macroscopic geometry of the radio source, andis expanding to the microscopic processes. In this paper, we present a summary of latter studies,
especially about the generation mechanism of electrostatic and electromagnetic 2fp waves and theelectron acceleration at the quasi-perpendicular shcok.
Omura et al. (2003) have studied the response of thermal plasmas to an induction electric field via
one-dimensional particle simulations. The induction electric field is assumed to be uniform in spaceand constant in time. Because of acceleration of electrons and ions in the opposite directions, there
arise counter streaming electrons and ions that cause the Buneman instability. Depending on the ratioof the ion temperature T i to the electron temperature T e , responses to the electric field are different.
For a case with hot ions (T i ≫ T e ) the Buneman instability leads to formation of large isolated
electrostatic potentials which trap some electrons to move with ions. For a case with colder ions (T i
≪ T e ) the Buneman instability is taken over by excitation of ion acoustic waves, which diffuse thelow-energy part of the accelerated electrons to stabilize the instability. However, a substantial part ofthe electrons are grouped together at the high-energy part, forming a distinct bump in the electron
distribution. In the present simulations we have found that the induction electric field can form anelectron beam along the magnetic field line. Since the electron beam leaves the region of theinduction electric field and moves into an unperturbed plasma, the accelerated electrons can cause abump-on-tail instability. This can lead to formation of electrostatic solitary waves as frequently
observed by the GEOTAIL spacecraft in the plasma sheet boundary layer (PSBL). The persistentobservation of the electrostatic solitary waves indicates their association with the induction electricfield that results from meandering motion of the current sheet in the magnetotail.
Krasovsky et al. (2002) studied the dynamics of high energy electrons in gyroresonance with aquasi-monochromatic circularly polarized whistler mode tracing a geomagnetic field line are studied
numerically.

The wavenumber and amplitude of the whistler wave are assumed to be slowly

varying functions due to the weak longitudinal inhomogeneity of the geomagnetic field.

Thespace-time dependence of the electromagnetic field manifests itself in the existence of an
approximate invariant of the electron motion.

Under the conditions characteristic of themagnetosphere, this invariant is found to be conserved with very high accuracy even in the processof resonant wave-particle interaction, whereas the constancy of the electron magnetic moment isstrongly violated in the resonance. The availability of the approximate constant of the motion

allows one to describe the gyroresonant wave-particle interaction with the aid of simpler equations
averaged over the fast Larmor gyration.
Matsukiyo et al. [2004] succeeded in reproducing the high-frequency electric wave spectra
observed in the auroral upward current region by one-dimensional particle-in-cell simulations. Using
distribution functions suggested by the measurements, they found that in the nonlinear state, ion
acoustic waves and electron two-stream (Langmuir) waves dominate the spectrum. In the absence ofcold electrons, electron acoustic waves are not excited initially but appear only at a late time. This isdue to the result of the formation of a two-temperature electron plasma by nonlinear interactions
when all other instabilities have saturated. However, owing to the weakness of these electron
acoustic waves, they are less important for the formation of electron holes and affect the particle
dynamics much less than the two-stream instability.
The formation process of ESW were studied by Umeda et al. [2002]. They conducted one- andtwo-dimensional electrostatic particle simulations with open boundaries. They inject a weak electron
beam from an open boundary into the background plasma to study spatial and temporal developmentof a bump-on-tail instability from a localized source. In the open system, spatial structures ofelectron holes vary depending on the distance from the source of the electron beam. They showed
the following scenario of the time and spatial evolution of ESW potentilas: In an early phase of thesimulation run, electron holes that are initially uniform in the direction perpendicular to the magnetic
field become twisted through modulation by oblique electron beam modes. As the electron holes
propagate along the magnetic field, they are aligned in the perpendicular direction throughcoalescence. Spatial structures of electron holes in a distant region from the source become
one-dimensional. In a long-time evolution of the instability, ion dynamics becomes important indetermining spatial structures of electron holes. A lower hybrid mode is excited locally in the region
close to the source of the electron beam through coupling with electron holes at the same parallel
phase velocity. The lower hybrid mode modulates electron holes excited in later phases, resulting information of modulated one-dimensional potentials.
Shin et al. [2004] showed the waveforms of the intense electrostatic waves observed in thedownstream

regionarequasi-monochromatic.

They

named

their

waves

Electrostatic

Quasi-Monochromatic (EQM) waves. By comparing the plasma wave data with electron data, theyfound the good correlation of the observations of EQM waves with beam-like cold electrons. Theysuggested that the EQM waves are electron acoustic mode waves based on the preliminary linear
dispersion analyses.
Deng et al. [2004] have provided possible evidence of multiple X lines collisionless reconnectionin the magnetotail at the microscopic level by combining the observations of plasma, magnetic field,
particles, and waves. On 11 December 1994 the Geotail spacecraft encountered an active
reconnection diffusion region around the X line in the Earth's magnetotail. Three interesting featureswere observed. One is quadrupole pattern of the out-of-plane By magnetic field component during
the passage of magnetic islands and the crossing of the neutral sheet. The second is a direction
reversal of the electron beams in the vicinity of the separatrix of the magnetic topology ofreconnection. The third is a clear plasma flow reversal.

H2.2 Wave Propagations

Hikishima et al. [2004] investigated the cyclotron resonance and pitch-angle diffusion of resonant
electrons by means of theoretical analysis and particle simulation involved in the generation andpropagation of chorus emissions in the Earth’s magnetosphere. The results indicate that the resonant
electrons with initially large pitch-angle anisotropy are rapidly pitch-angle diffused by a generated
whistler mode wave, and the subsequent anisotropy decrease saturates the wave growth.
H2.3 Shocks and Particle Acceleration

Nishimura et al. [2004] studied the acceleration and heating of electrons at quasi-parallel shockwaves by means of a one-dimensional full particle computer simulation. Our simulation shows thatthe ion beam instability due to the anomalous cyclotron resonance excites whistler mode waves in
the upstream region. When the Mach number becomes large beyond a critical value, the whistler
wave packets do not appear. The electron acceleration parallel to the magnetic field results from theparallel electric fields caused by both the whistler mode waves and the electrostatic shock potential.
The potential concerning the parallel electric field increases with Mach number below the critical
Mach number but is relatively independent of the Mach number beyond the critical Mach number.
This verifies that the contribution of the whistler waves to the parallel acceleration is as important asthat of the electrostatic shock potential below the critical Mach number. Also, the spatial profile ofthe potential concerning the parallel electric field is clearly correlated with the magnetic field profile.
Downstream, the electron temperature is anisotropic such that the parallel temperature is larger thanthe perpendicular temperature. The Mach number dependence of the electron parallel temperature
can be evaluated from the viewpoint of a wave-particle interaction (current-driven instability).
Nishimura et al. [2003] investigated the properties of reformation in perpendicular collisionlessshocks by means of a one-dimensional particle-in-cell simulation. Reformation is associated with ionreflection at the shock ramp and subsequent ion gyromotion in the upstream region. However, if ionsare reflected continuously at the ramp, why does the shock reform intermittently at sufficiently highMach number? The simulations show that the shock potential changes dramatically through there-formation cycle, so that it is this potential variation which leads to the intermittent response of theshock.
Katoh et al. [2003, 2005] studied particle acceleration processes due to wave particle interactions
by employing numerical simulations based on a hybrid algorithm in order to investigate the merging
process of cometary oxygen ions into the solar wind and verify a elementary process of energizing
mechanism of relativistic electrons in the outer radiation belt during a geomagnetic storm recovery
phase. Katoh et al. [2003] carried out one-dimensional hybrid simulation, whose results revealed thata spatial extent of interaction region surrounding comet nucleus is deeply related to the ion beam
instability driven by a field aligned motion of picked-up ions. By utilizing a newly developed
simulation scheme named as ‘electron hybrid code’, Katoh et al. [2005] investigated pitch angle andenergy diffusion processes of relativistic electrons through the resonant interaction by comparing
results of the numerical experiment and the quasi-linear theory under the same condition of theinteraction between whistler mode waves and high energy electrons. The difference between theirresults suggests the importance of the verification of the theory under the realistic plasma condition
corresponding to the observed parameters in the real magnetosphere.
Nishimura et al. [2002] studied the acceleration and heating of electrons at quasi-parallel shockwaves by means of a one-dimensional full particle computer simulation. Their simulation shows thatthe ion beam instability due to the anomalous cyclotron resonance excites whistler mode waves in
the upstream region.

The electron acceleration parallel to the magnetic field results from theparallel electric fields caused by both the whistler mode waves and the electrostatic shock potential.
They found that the contribution of the whistler waves to the parallel acceleration is as important asthat of the electrostatic shock potential below the critical Mach number.
The properties of reformation in perpendicular collisionless shocks were investigated by
Nishimura et al. [2003] using one-dimensional particle-in-cell simulation. The reformation is known
to be associated with ion reflection at the shock ramp and subsequent ion gyromotion in the
upstream region. However, it is also known that the shock reforms intermittently at sufficiently
high Mach number if ions are reflected continuously at the ramp.

The simulations were performed

to investigate this issue and they found that the shock potential changes dramatically through there-formation cycle, so that the potential variation leads to the intermittent response of the shock.
Hada et al. [2003] analyzed the shock front nonstationarity of perpendicular shocks insuper-critical regime by examining the coupling between "incoming'' and "reflected'' ion populations.
For a given set of parameters including the upstream Mach number and the fraction alpha ofreflected to incoming ions, a self-consistent, time-stationary solution of the coupling between ion
streams and the electromagnetic field was sought. The analytic results were in good agreementwith full particle simulations for low beta case.
Futaana et al. [2003] studied the nonthermal ions which were measured by Particle Spectrum
Analyzer/Ion Spectrum Analyzer (PSA/ISA) on board the Nozomi when the spacecraft was veryclose to the Moon. It was found that the nonthermal ions were protons and had a partial ring
structure in the phase space.

By conducting particle tracing calculation, their source location was

found to be the dayside of the Moon, and the nonthermal ions seem to have large velocities when
they were generated. It was proposed that the electromagnetic field in the vicinity of the Moon musthave a dynamic structure, possibly a miniature bow shock associated with a local magnetic anomaly,
where some of the solar wind protons are deflected to forms a partial ring structure in the velocity
phase space.
Cross field diffusion of energetic particles (cosmic rays) in a two-dimensional static magnetic
field turbulence is studied by Otsuka and Hada [2003] by performing test particle simulations.
Qualitatively different diffusion processes were observed depending on the ratio of Larmor radius tothe correlation length of the magnetic field fluctuations. The diffusion was found to be composed ofseveral regimes with distinct statistical properties, which can be characterized using Levy statistics.
Lembege et al. [2004] published a review to address a subset of unresolved problems incollisionless shock physics from a theoretical and/or numerical modeling point of view. The topics
are the nonstationarity of the shock front, the heating and dynamics of electrons through the shock
layer, particle diffusion in turbulent electric and magnetic fields, particle acceleration, and theinteraction of pickup ions with collisionless shocks.

H2.4 Nonlinear Effects

Usui et al. [2002] studied a three-wave coupling process occurring in an active experiment of
microwave power transmission in the ionospheric plasma by performing one-dimensional
electromagnetic particle simulations.

In the simulations, low-frequency electrostatic bursts are

discontinuously observed in space. The discontinuity of the electrostatic bursts is accounted for by
the local electron heating due to the bursts and the associated modification of the wave dispersion
relation.

They found that the character of the electrostatic bursts essentially differ for cases inwhich pump wave propagates either parallel or perpendicular to the geomagnetic field.
Krasovsky et al. [2003] considered the electrostatic pulses recorded by the Geotail spacecraft andlabeled electrostatic solitary waves (ESW) within the framework of Bernstein-Greene-Kruskal(BGK) solitons. The general approach developed in the article applies to arbitrary particle
distributions of the background plasma, velocities of the BGK solitons and wide variety of therecorded ESW waveforms. The new models and physical interrelations reveal universal features of
the BGK soliton structure and allow a direct juxtaposition with the observations. The establishedinterconnections between the physical characteristics of the waves agree well with the Geotail dataon ESW waveforms
Generation of electrostatic multiple harmonic Langmuir modes during beam-plasma interaction
process has been observed in laboratory and spaceborne active experiments, as well as in computer
simulation experiments. Despite earlier efforts, such a phenomenon has not been completely
characterized both theoretically and in terms of numerical simulations. Yoon et al. [2003] foundanalytic expressions for harmonic Langmuir mode dispersion relations and compared their resultswith numerical simulation results.
Gaelzer et al. [2003] developed generalized weak turbulence theory in which

multiharmonic

Langmuir modes were included and the self-consistent particle and wave kinetic equations weresolved. The result shows that harmonic Langmuir mode spectra exhibit a quasi-power-law feature,
implying multiscale structure in both frequency and wave number space spanning several orders ofmagnitude.
The generation of harmonic Langmuir modes during beam plasma interaction was studied by
Umeda et al. [2003] with nonlinear theoretical calculations and computer simulations. In their
Vlasov simulation code, multiple harmonic Langmuir modes up to 12th harmonics can be included
in contrast to previously available simulations which were restricted to the second harmonic only.
The frequency-wave-number spectrum obtained by taking the Fourier transformation of simulated
electric field both in time and space showed an excellent agreement with the theoretical nonlinear
dispersion relations for harmonic Langmuir waves. The saturated wave amplitude features aquasi-power-law spectrum which reveals that the harmonic generation process is an integral part ofthe Langmuir turbulence.
Krasovsky et al. [2004] studied the electrostatic pulses observed by satellites in space plasmas
with the concept of electron phase density holes to clarify the qualitative differences between theactual three-dimensional (3-D) perturbations and the well-known 1-D Bernstein-Greene-Kruskal(BGK) modes of the electron hole type. They showed that the anisotropy caused by the geomagnetic
field is a decisive factor and the hole-like structures is closely connected with thequasi-one-dimensional nature of the electron motion, predominantly along the external magnetic
field.
A linear analysis and 2-1/2dimensional electromagnetic full-particle simulations were performed
by Fujimoto and Machida [2003] to investigate mechanisms of an electron heating due to an intenseHall current, which is caused by a large velocity difference between electrons and ions in the outflow
region inside the diffusion region of the magnetic reconnection. The numerical solution of the kinetic
dispersion relation predicted an unstable mode varies according to the electron-ion relative velocity
Vd; the kinetic cross-field streaming instability (KCSI) is dominant when Vd is under the substantial
fraction of the electron thermal velocity ve, while the electron cyclotron drift instability (ECDI) is
first excited for the case where Vd exceeds the critical velocity. It was shown that electrons areheated parallel to the ambient magnetic field due to the KCSI and perpendicularly due to the ECDI.
In particular, electrons are very quickly heated up to a high temperature when the ECDI is dominant.
However, the electron heating is ineffective when Vd/ve < 1.
Shklyar and Matsumoto [2002] studied the initial problem of plasma wave dynamics in thepresence of a sharp density jump that divides the space into transparent and opaque regions. A wave
packet was assumed to be initially localized in the transparent region. The transient process of field
penetration beyond the density barrier during the wave packet reflection from the density jump wasinvestigated. Signal velocity beyond the barrier was defined as the speed at which some small, but
finite, value of the field amplitude appearing in the evanescent region. This velocity was determined
analytically for the case of quasi-Gaussian wave packet. Also insight into the field dynamics inopaque region was gained by considering a steplike initial wave packet.
In order to self-consistently study the kinetic processes at the Venus ionopause, Terada et al.
[2002] calculated the Venus ionopause-solar wind interaction region kinetically, including theionosphere, ionopause transition layer, magnetosheath, and solar wind, by applying boundary-fitted
coordinates to the particle-in-cell code. They found that the distribution of ionopause surface waves
generated by the Kelvin-Helmholtz(K-H) instability exhibits a clear asymmetry between

hemispheres of upward and downward solar wind motional electric fields. Accordingly, theasymmetrical momentum transport across the ionopause yields an asymmetrical convection patternof the ionosphere.

Terada et al. [2004] extended their work to study a viscous process associated with the K-H
instability around the ionopause, which is less well understood compared to the pickup process of
exsospheric ions and electrons. They studied the relative importance of the escape processes for thecase of low solar wind dynamic pressure

as well as for the high dynamic pressure case, andshowed the viscous removal process occurring at the ionopause plays a significant role in the ion
escape from Venus. Their model also suggests the asymmetrical appearance of "disappearing
nightside ionosphere".
A merging process of cometary oxygen ions into the solar wind particle was studied by Katoh et al.
[2003] employing numerical simulations based on a hybrid algorithm.

The results of

one-dimensional hybrid simulation shows that a spatial extent of interaction region surrounding
comet nucleus is deeply related to the ion beam instability driven by a field aligned motion ofpicked-up ions.
Katoh et al. [2005] investigated pitch angle and energy diffusion processes of relativistic electrons
through the resonant interaction by comparing results of the numerical experiment and thequasi-linear theory under the same condition of the interaction between whistler mode waves andhigh energy electrons. The difference between their results suggests the importance of theverification of the theory under the realistic plasma condition corresponding to the observed
parameters in the real magnetosphere.
Matsukiyo and Hada [2002] studied a long time evolution of cyclotron maser instability at nullwave number (k=0) which is destabilized by relativistic ring distribution of plasma through thecyclotron resonance.

They performed particle simulations using a plasma which consists ofrelativistic ring electrons, background positrons, and background electrons. The linear and nonlinear
stages of the system evolution were examined for both gyrotropic and nongyrotropic ring
distributions. The linear theory predicts that, when the initial ring energy is strongly relativistic,
there appears a critical initial ring momentum at which the system is marginally stable. Numericalsimulations show, however, that the system is nonlinearly unstable even when the initial ring
momentum exceeds the critical momentum. The final saturation level of the wave energy was
obtained analytically.
Matsukiyo and Hada [2003] examined the dispersion relation and nonlinear evolutionof the parametric instabilities of circularly polarized Alfven waves in a relativistic
electron-positron plasma. First, the nonlinear dispersion was solved in a nonrelativistic
limit, then the weakly relativistic effect was examined. The one-dimensional fullparticle simulation and bicoherence analysis of the simulation result suggest thatsuccessive decay via the interaction between the parallel propagating Langmuir-likewave and antiparallel propagating Alfven-like wave can efficiently generate acontinuum of low frequency electromagnetic waves, which can interact with energetic
particles.
H2.5 Active Experiment and Spacecraft-Environment Interaction

Using topside sounder data obtained by the Ohzora (EXOS-C) satellite, Uemoto et al. [2004]
investigated the structure and dynamics of the ionization ledge in the equatorial topside ionosphere.
They found that the ionization ledge observed in the local noon time period shows similar nature as
it has been theoretically predicted for the F3 layer. Also they indicated that the seasonal dependenceof the occurrence probability of the ionization ledge has a tendency contrary to that of the F3 layer.
Usui et al. [2004a, 2004b] for the first time applied electromagnetic PIC (Particle-In-Cell)computer simulations to analyze the antenna characteristics in magnetized plasma. They particularly
examined the electron kinetic effects on the antenna impedance. It is confirmed that the mostobvious resonance point is the local Upper Hybrid Resonance frequency. As the electron temperature
increases, the resonance frequency also increases in accordance with the modification of dispersion
relation for the UHR branch. They also examined the electromagnetic environment of the sheathregion created at the antenna surface by performing EM-PIC simulations. They could basicallyconfirm the sheath waves propagating along the metal-plasma interface at the frequencies lower thanthose of normal wave modes for uniform plasma with no external magnetic field. In magnetizedplasma, They also could observe the sheath waves below the Upper Hybrid Resonance frequency.
They could also confirm unidirectional waves propagating below the UHR frequency.
Numerical simulations on active perturbation of space environment by microwave powertransmission (MPT) and plasma beam emission for the spacecraft charging control have been
performed.

Usui et al.[2002] studied a three-wave coupling process occurring in an active

experiment of MPT in the ionospheric plasma by performing one dimensional electromagnetic PIC(Particle-In-Cell) simulations. Continuous emission of intense electromagnetic waves from anantenna located at a simulation boundary excites a low-frequency electrostatic wave as the result of anonlinear three-wave coupling. They also found that the low-frequency electrostatic bursts are
discontinuously observed in space. The discontinuity of the electrostatic bursts is accounted for by
the local electron heating due to the bursts and the associated modification of
the wave dispersion relation.

Usui et al. [2004c] also studied the basic process of the spacecraft

charging and its neutralization using dense plasma emission by performing PIC simulations.

They

particularly examined the electron/ion flux to the charged body and the corresponding potential
variation. It is shown that the negatively charged body is neutralized mainly by the enhancement ofion flux of the emitted plasma In the transient process of the charge neutralization, they found very
turbulent current variation at the emitted plasma cloud region, which may cause electromagnetic

perturbation in the vicinity of the body.
Using topside sounder data obtained by the Ohzora (EXOS-C) satellite, Uemoto et al. [2004]
investigated the structure and dynamics of the ionization ledge in the equatorial topside ionosphere.
They found that the ionization ledge observed in the local noon time period shows
similar nature as it has been theoretically predicted for the F3 layer. Also they indicated that theseasonal dependence of the occurrence probability of the ionization ledge has a tendency contrary tothat of the F3 layer.

H2.6 Techniques of Data Analysis and Computer Experiments
Akimoto et al. [2003] developed a new general-purpose computational technique for classifying
the plasma waves in a systematic way from database of scientific satellite. Firstly, we propose a
two-step cluster analysis for the classification. Applying this cluster analysis to the key parameters of
the Akebono wave data, we could make some representative classes of wave phenomena with asmall amount of calculation time. In order to determine the suitable number of representative class,
we propose an evaluation function with AIC.

Finally, we discriminated to the representative classes

and exception.
Kasahara et al. [2002] introduced new computational techniques for extracting the attributes
and/or characteristics of the plasma waves and particles from the enormous scientific database.
These techniques enable us to represent the characteristics of complicated phenomena using a few
key-parameters, and also to analyze large amount of datasets in a systematic way. These techniques
are applied to the observational data of the ion heating/acceleration phenomena in the auroral region
obtained by the Akebono satellite. Finally we evaluate our algorithms through some correlation
analyses between waves and particles and demonstrate their availability.
Tanaka et al. [2004] developed a general-purpose system which manages and provides various
kinds of information accumulated in our university. One of the most important points in the designof the system is management of the enormous amount of data, which comes up to several tera-bytes
in the field of natural science in some cases. In the present study, we constructed a database systemon the geospace radio environment obtained by the Akebono satellite. This is a model case ofenormous database systems especially in natural science because there are huge and variety kinds ofdata on the space environment measurement. In the paper, we introduced the system and evaluatedthe performance.
The lunar radar sounder (LRS) experiment onboard SELENE (SELenological and ENgineering
Explorer) has been planned for observation of the lunar surface and subsurface structures. The
computer simulation of the LRS observations and development of data analysis method have been
performed by Kobayashi et al. [2002a] using newly developed simulation code, Kirchhoffapproximation sounder simulation (KiSS) code. It has been shown by the simulation that thesubsurface echoes are detectable by using data stacking technique. Kobayashi et al. [2002b] has also
performed the simulation of the LRS observations in the lunar highland regions, where subsurface
echoes are severely masked by confusing surface echoes. The application of the synthetic apertureradar (SAR) method for subsurface echo analysis in the lunar highland region has been proposed
based on the simulation results.
One of the most important methods for the studies of plasma waves observed by spacecraft is tocompare them with other observations either with same spacecraft or with other spacecraft.
Simultaneous ground-based observations also help our understandings of the plasma wave
generation mechanisms. Murata [2003] and Murata et al. [2002a] have constructed a softwaresystem (STARS) to gather observation data files individually managed at several organizations. It
also provides a variety of functions to plot and analyze the data. For 3-dimensional data analyses ofthe observation data, a virtual Earth’s magnetosphere system (VEMS) is produced by Murata et al.
[2004b].
Murata et al. [2002b], Murata et al. [2002c], Murata [2002d] and Murata et al. [2002e] havedeveloped systems to achieve high-performance computing and to support computer simulations forplasma particle simulations.

References（別ファイル）