Commission H (Waves in Plasmas) Activity Report
July 15th, 2005
T. Okada, Y. Omura, and H. MatsumotoResearch Topics<AKEBONO>
Kumamoto et al. [2004] investigated Long-term variations of ambient electron number density in thenightside auroral region based on auroral hiss data observed by the PWS. The electron number density inthe nightside auroral region shows clear dependence on solar activity. The figures show the altitude profilesof electron number density during solar maximum (left figure) and during solar minimum (right figure).
The number density during solar maximum is 3-10 times larger than that during solar minimum. The
vertical profile of scale height, which is associated with plasma composition and temperature, also depends
on the solar activity.

Hikishima et al.[2005] investigated the generation and propagation mechanisms of the chorus
emissions by the cyclotron interaction between whistler mode
waves and anisotropic electrons.X This is the result by
one-dimensional particle simulation with dipole typeinhomogeneous magnetic field. The whistler mode waves are
generated from back ground noise in the region where themagnetic field is the weakest and are propagating to the direction
away from the region. This is much like the theory andobservation of the chorus emissions.

<GEOTAIL>GEOTAIL spacecraft has been operated since 1992. The Plasma Wave Instrument (PWI) is continuously
collecting spectrum data and high time-resolution waveform data. It is expected to be in a good condition atleast until the next long eclipse in 2005.The 24 hour plots of the observed wave spectrum data are openedin the PWI web site http://www.rish.kyoto-u.ac.jp/gtlpwi, and http://www.stp.isas.jaxa.jp/geotail.
Shin K. et al. (2005) observed the electrostatic quasi-monochromatic (EQM) waves which frequency
range is near 1 kHz. Geotail spacecraft observations show good correlation of EQM wave activities withthe existence of cold electron beam-like component which correspond to the electrons accelerated in the
bow shock. They show that under the existence of the cold beam-like component and background electrons

with different temperatures, most plausible wave mode of the EQM waves is electron acoustic wave.

Figure: (a) Waveforms of the EQM waves of the parallel and the perpendicular components with respect
to the ambient magnetic field (left panel) and corresponding hodograph (right panel) for the period of 40
milliseconds from 5:13:42.492 UT on January 15, 1995. (b) Electron velocity distribution for the January
15, 1995 event observed at 5:13:29 UT. Figure shows the cut through f(v) along the ambient magnetic field
The positive velocity is referred to the ambient magnetic field direction. The beam-like component isdisplayed by arrow.

Antenna in Space Plasma
Higashi et al. (2005) studied the characteristics of dipole antenna or probe antenna, namely the antenna
impedance and effective length using the AKEBONO and GEOTAIL observation data. The impedance of
the wire dipole antennas onboard the Akebono satellite is estimated by using the electromagnetic fieldobservations for Omega navigational signals. The estimated capacitance and resistance exhibit specific spin
variation, which would be caused by the plasma sheath formation around the antenna wires depending on
the angle between the antenna direction and the geomagnetic field line. The figure shown below indicates adependence of antenna impedance to the angle on the geomagnetic field. The effective lengths of two
orthogonal sets of wire dipole antennas are estimated to be nearly the half of its tip-to-tip length of 60 m,
which is consistent with the conventional assumption of the effective lengths of the dipole.

Figure: Experimental results
showing the dependence ofantenna
impedanceonthegeomagnetic field (Higashi et al.,2004).

<SELENE>
The Lunar Radar Sounder (LRS) experiment onboard the SELENE consists of three subsystems; SDR(sounder), NPW (natural plasma wave) and WFC (waveform capture). SDR will provide subsurface
stratification and tectonic features in the shallow part (several km depth) of the lunar crust, by using an
FM/CW radar technique in HF frequency range. NPW and WFC will observe planetary radio waves andnatural plasma waves in the frequency range from 20kHz to 30MHz and from 100Hz to 1MHz,
respectively.

The mission instruments are now in the stage of
1.5th system function test at Tsukuba Space center. The
system function tests and EMC (Electromagnetic
Compatibility) tests are scheduled from March to
September. After the system function test, theinstruments will have last opportunity for final
adjustments. Figure @ shows the LRS instrument in
the RF test at the Tsukuba Space Center in December
2004 (report by Ono and Kumamto).

<Rocket Experiment>
Application of MF waves to Ionospheric Plasma measurement
Ashihara et al. (2005) measured the electron number density in the mid-latitude D-regeon ionosphereand found an thin layer of enhanced electron density by using the MF radio absorption method. The
S-310-33 rocket was launched at 0:30 JST on 18th January, 2004.
The Medium Frequency Receiver (MFR) was installed onthe tomeasure the intensities of radio waves at 238 kHz and 873 kHz
transmitted from the ground stations. The electron density profile wasestimated from absorption of these radio waves. It is found that there
was a thin layer of high electron density of 2.4×103 cm-3 at thealtitude of 89 km. The thickness of its layer is about 0.9 〜 1.0 km.
The left figure shows the electron density profiles estimated by threedifferent methods: The thick line indictes the one estimated by therocket experiment using MFR, the broken line by probe method, andthe thin line is by the IRI 2001 model. The MFR rocket experimentgives the existence of thin layer of high electron density.
<New Technology>

Ishisaka et al. (2005) measured the electron density in the very low altitude as low as 50km by the
MF radio absorption method. The SRP-4 rocket was launched at 12:07 LT on 18 March 2002. The Low
frequency and Medium frequency band radio Receiver (LMR) and the DC Probe System (DPS) were
installed on-board the rocket to estimate the D-region electron density. The LMR measured theintensities
of radio waves received from ground-based stations operating at 257 kHz, 660 kHz and 820 kHz,
respectively.
The electron density profile at altitudes below 90 km wasestimated from the measured absorption of these radio waves. It
was found that the electron density began to increase at the altitudeof 52 km and was larger than that estimated by the International
Reference Ionosphere model at altitudes from 74 km to 89 km. The
estimated electron density profile from 40 km to 95 km is shown in
the figure, where the broken line is the one obtained by the IRI
model

<Polar Region Experiments>
 Polar Patrol Balloon (PPB) Experiment
Miyake et al. [2004] carried out successfully the PPB experimentin Antarctica in January 2003, and recently reported theobservational results such as the Pc1 pulsations, ELF hiss, polarchorus and auroral hiss. In the PPB experiment, two challenging
techniques for the data transmission were carried out. First, all theobserved data were transmitted directly from the balloons to
National Institute of Polar Research in Japan, by way of the
IRIDIUM satellites for the world-wide mobile telephone. We could
get the new observed data within 30 minutes due to this satellite datatransmission system. Second, the electromagnetic wave receiver(EMW) in sub gondola were placed just beneath the balloon, 100m
away from the main gondola, in order to avoid electromagnetic
noises emitted from the various instruments onboard the main
gondola. The data observed by EMW are transmitted from the sub
gondola to the main gondola by use of wireless modem. The
observation times of receivers between onboard multiple balloons are synchronized in 10ms by using the
1pps pulse signals emitted from GPS satellites. Both data transmission systems have been worked properly,
and contributed to obtaining precious scientific data in the Antarctic region.
Ground Observation
Ozaki et al. [2005] plan to make the multipoint observations of ELF/VLF waves by low power
magnetometer systems in Antarctica for the study of whistlers and ELF/VLF emissions in December 2005
to December 2006. The magnetometer systems will be placed at three sites, West Ongul (69°01'06''S 39°
30'28''E), Skallen (69°40'24''S 39°24'07''E), and H100 (69°17'44''S 41°19'15''E) unmanned stations.
Each system consists of two crossed vertical loop antennas and a multi-channel analyzer which measurescontinuously with 1 minute resolution the mean power and polarization of NS and EW magnetic
components in 4 spaced frequency bands (500, 1 k, 2 k and 6 kHz). The recorded data are sent back to
Kanazawa through IRIDIUM satellite communication. With this system, we will be able to investigate thedynamic structure of ionospheric exit points of natural ELF/VLF waves.

Seismic Radio Emissions
Higashi et al.,{2005} studied the anomalous electromagnetic signals onboard satellite in the ionosphereand the lower magnetosphere over seismic areas. In order to estimate the wave intensities related withseismic activity, they performed a numerical analysis of the electromagnetic waves in the lower ionosphereradiated from an underground transient dipole source.
Figure 1 (a) shows the spatial evolution of the horizontal (north-south component of) electric field Ey.
Each figure shows the intensity distribution of the Ey over the horizontal north-south range of ±100-km
and at the altitude range of 0- to 120-km above the epicenter. Also the spatial evolution of the horizontal(east-west component of) magnetic field Bx is shown in Figure 1 (b). The waves are slightly reflected at thealtitude of about 80 km. It is seen that a specific null appears above the epicenter in both Figures 1 (a) and(b), and the electromagnetic field intensities have a north-south asymmetric distribution above the altitudeof 70 km in the lower ionosphere, due to the whistler-mode propagation along the geomagnetic field lines.

(a)

(b)

<New Technology>
Ueda et al. [2004]developed a Digital Wave Particle Correlator (DWPC) system. The designed system isassembled in one FPGA (Field Programmable Gate Array) IC. For a new electron instrument in thedevelopment stage, FPGA is installed in many latest rocket and spacecraft to combine multi-channel,
multi-frequency range array of correlators with technical improvements.
They realized 3-channel of variable
waveform filter and data synchronization withwaveform and particle in the DWPC system. In
FPGA, the algorithm controls waveform data,
particle data, and magnetic field data. A
practical application of such a wave-particle
correlation system is important in the spacescience mission. For example, the electron
bunching generates plasma waves, packet-likelangmuir waves generated in the polar aurora orin the solar wind. This instrument can observewave-particle
interactions
byonboardcalculation of the cross correlation functions
between the obtained waveforms and detectedparticles.
Picture shows the test board of
Digital Wave Particle Correlator.

Reference
Ashihara Y., K. Ishisaka, T. Okada, T. Miyake, and Y. Murayama, “Estimation of electron density with MF
radio receiver (MFR)€35, JAXA Special Report SP-04-007, 2005
Ueda Y. et al., ISSS7 (The 7th International School/Symposium for Space Simulations)
Higashi R. et al., “The characteristics of crossed wire antennas onboard the Akebono satellite”, IEICE
Trans. Commun, Vol.J88-B, No.2, pp.442-450, 2005.
Hikishima M, Satoshi Yagitani, Isamu Nagano, Yoshiharu Omura, Hiroshi Matsumoto, “Particlesimulation of cyclotron interaction of chorus in a nonuniform magnetic field€35, XXVIIIth URSI General
Assembly, New Delhi, India, October 23-29, 2005.
Ishisaka K., T. Okada, J. Hawkins, S. Murakami, T. Miyake, Y. Murayama, I. Nagano, and H. Matsumoto,“Investigation of Electron Density Profile in the Lower Ionosphere by SRP-4 Rocket Experiment€35,
Accepted in Earth, Planets and Space.
Kumamoto, A., T. Ono, and M. Iizima, “Seasonal and solar cycle dependences of ambient plasma density
in the polar magnetosphere”, 35th COSPAR Scientific Assembly, Paris, France., p.3398, 2004
Miyake, T., T. Okada, H. Yamagishi, A. Chino, K. Ishisaka, T. Yamagami, "Development of ELF/VLF bandwave receiver onboard Polar Patrol Balloon",IEICE Trans. on Communication B, vol.J87-B, No.5,
pp.741-745, 2004
Ozaki M.,, Isamu Nagano, Satoshi Yagitani, Hisao Yamagishi, Natsuo Sato, and Akira Kadokura, “Groundbased multipoint observations of natural ELF/VLF waves in Antarctica”, The 29th Symposium on Spaceand Upper Atmospheric Sciences in the Polar Regions, Tokyo, August 2005.
Ozaki M.,, Isamu Nagano, Satoshi Yagitani, and Kazutoshi Miyamura, “Time Evolution of Seismic
Electromagnetic Wave Emission by Full-Wave Analysis”, XXVIIIth URSI General Assembly, New
Delhi, India October 2005.
Shin K. , H. Kojima, H. Matsumoto, and T. Mukai , “Electrostatic quasi-monochromatic waves downstreamof the bow shock: Geotail observations”, COSPAR COLLOQUIA SERIES Vol.16, Frontiers in
Magnetospheric Plasma Physics, pp. 293-296, 2005.

Conferences and Meetings ( February 2005 –July 2005)
1) Third International Symposium on the Arctic Research and eventh Ny-Alesund Scientific Seminar,
Tokyo, Japan, February 22-24, 2005
2) International Workshop on Seismo Electromagnetics, Tokyo, Japan, March 15-17, 2005.
1) Magnetospheric ULF Waves (Chapman), San Diego, CA, USA, March 21-25, 2005
2) 7th International School/Symposium for Space Simulations, Kyoto, Japan, March 26-31, 2005
3) ISSS-7, Kyoto, March 26-31, 2005 http://www.rish.kyoto-u.ac.jp/isss7/4) International Workshop on Space Weather - On the Causes of Southward Interplanetary Magnetic
Field (IMF), Tokyo, Japan, April 4, 2005.
5) 9th Spacecraft Charging Technology Conference, Tsukuba, April 4-8, 2005,
6) European Geosciences Union General Assembly , Vienna, Austria, April 24-29, 2005
7) Joint meeting for Earth and Planetary Science 2005, Chiba, Japan, May 22-26, 2005.
8) Spring AGU Meeting New Orleans, May 23-27, 2005
9) AGU 2005 Joint Assembly, Louisiana, USA, May 23-27, 2005
10) Asia Oceania Geosciences Society's 2nd Annual Meeting (AOGS 2005), June 20-24, 2005,
Singaporean (http://www.asiaoceania-conference.org/)

Future Conferences and Meetings11) IAGA 2005 Scientific Assembly, Toulouse, France, July 18-29, 200512) International Symposium on Antenna and Propagation (ISAP2005), Seoul, Korea, August 3-5, 2005
13) Cluster and Double Star Symposium: 5th Anniversary of Cluster in Space, ESA/ESTEC, Noordwijk,
The Netherlands, September 19-23 200514) 7th Asia Pacific Plasma Theory Conference (APPTC), July12-15, 2005 http://www.tcsc.nifs.ac.jp/icnsp
15) IAGA&ICMA,
Tourouse,July
18-29,
2005
http://www.iugg.org/IAGA/index.htm
http://www.copernicus.org/IAGA/2005/index.htm
16) 9th IAMAS Scientific Assembly, Beijing, August 2-11, 200517) The Magnetospheres of the Outer Planets
University of Leicester August 7-12, 2005
http://ion.le.ac.uk/mop18) CAWSES workshop September 12-13, 2005 http://www.stelab.nagoya-u.ac.jp/~scostep
19) SGEPSS, Kyoto Univ., September 28-October http://www.kurasc.kyoto-u.ac.jp/sgepss/LOC/
20) IAA
International
Conferenceon
Low-Cost
Planetary
Missions
Kyoto Research Park, 1 October 1-13, 2005 http://www.hayabusa.isas.jaxa.jp/iclcpm2005/21) XXVIIIth International. Union of Radio Scnence [URSI], New Delhi, October 23-29, 2005
http://www.ursiga2005.org/
22) AGU fall meeting, San Fransisco, December 5-9, http://www.agu.org/meetings/fm05/
23) European Geosciences Union General Assembly, Vienna, April 2-7, 200624) 36th COSPAR, Beijing, July 16-23, 2005 http://www.copernicus.org/COSPAR/COSPAR.html
25) Western Pacific Geophysics Meeting, Beijing, 24-28 July, 2006 http://www.agu.org/meetings/wp06/