Commission H (Waves in Plasmas) Activity Report
November 15th, 2004
T. Okada, Y. Omura, and H. MatsumotoResearch Topics<Akebono>
Based on the plasma wave data by AKEBONO spacecraft over 15 years, the mapping of VLF
wave activity in the inner geospace has been elucidated (Kasahara et al., 2004). An example of suchtime variation of electric wave intensity during the geomagnetic storm time in the frequency range
from 1 to 10kHz is shown in Figure 1. The plasma wave data obtained by the instruments PWS andVLF are available on request [for further information: http://www.stp.isas.jaxa.jp/akebono].

Figure 1
Vertical axis indicates the L-valueof the observation point, and thehorizontal axis indicates the relative
time from the beginning time of thestorm recovery (Kasahara et al.
2004).

One of the hot topics in the inner magnetosphere physics is the origin of relativistic electrons in
the outer radiation belt. One of the plausible mechanisms is wave-particle resonant diffusion bywhistler mode chorus during recovery phase of magnetic storm is one of hot topics. Using Akebono
VLF and RDM data, several works related to the topic are performed and some interesting results
were demonstrated so far.

<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 at least until the next long eclipse in 2005.The 24 hour plots of the observed
wave spectrum data are opened in the PWI web site http://www.rish.kyoto-u.ac.jp/gtlpwi, andhttp://www.stp.isas.jaxa.jp/geotail.

<Antenna in space plasma>
The characteristics of dipole antenna or probe antenna have been studied in two ways; one is theconstruction of electrical equivalent circuit using the AKEBONO and GEOTAIL observation data.
Figure 2 shows a dependence of antenna impedance to the angle on the geomagnetic field (Higashiet al., 2004). Another approach is the computer simulation using the particle code. Usui et al. havebeen studying the antenna properties of a dipole antenna immersed in magnetized plasma byperforming PIC (Particle-In-Cell) electromagnetic simulations. In the simulation, the effect of theplasma temperature and sheath size around the antenna are taken into account.

Figure 2
Experimental result
showing the dependence ofantenna impedance on thegeomagnetic field(Higashi et al., 2004).

Figure 3
Depencence of antenna
impedancebyobtained

Particle-In-Cellsimulations (Usui et al.,2004).

<SELENE>
SELENE spacecraft will be launched in 2006. After the 1st system function and EMC tests
performed from August 2003 to January 2004, each scientific instrument is now in the final
adjustment stage and next system function test will start in January 2005. For the delivery, onboard
software is now under development to install various kinds of intelligent functions, such as datacompression and data selection algorithm.
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
natural plasma waves in the frequency range from 20kHz to 30MHz and from 100Hz to 1MHz,respectively.

<BepiColombo>
The BepiColombo is the science mission to Mercury. It is the first collaborative science mission
between JAXA and ESA.The BepiColombo mission consists of two individual spacecraft called
MPO (Mercury Planetary Orbiter) and MMO (Mercury Magnetospheric Orbiter). The Announce ofOpportunity(AO) for the MMO spacecraft was issued by JAXA in April 2004.
ScientistsinJapanandEurope

jointly

proposed the plasma wave observation systemcalled PWI (Plasma Wave Investigation) in theresponse to the AO for MMO. The Principal
Investigator of PWI is Prof. Hiroshi Matsumotoin Kyoto university, Japan.After reviewing thePWI proposal, the MMO Payload

ReviewCommittee in JAXA selected the PWI for thescience payload onboard MMO spacecraft. PWI
investigates plasma/radio waves andDCelectric field in Mercury magnetosphere. The
MMO launch is scheduled in 2012.
Illustration of MMO (Mercury Magnetospheric Orbiter

<Ionospheric sounding by Radio Waves>
The ionospheric sounding S-310-33 rocket experiment was successfully conducted at
Kagoshima Space center, JAXA on January 18th. The MF wave (NHK Kumamoto BroadcastingStation; 873 kHz) was observed and using the wave absorption method, the electron number
density profile was estimated. An usual enhancement of electron density was found to exist ataltitude below 90 km during night time, which cannot be sensed either by the conventional
ionosonde nor the MF radar (Ashihara et al., 2004). The left of Figure 4 shows the wave intensity
observed along the upgoing rocket trajectory, and the right, the estimated electron number density.
Thiskindimportantofexperimentisto improve the Internati

onal Reference Ionosphere (IRI)
model at altitudes below 90. For thesame aim, a rocket experiment athigh latitudes is now under designby the Alaska Student Rocket
Project (ASRP) team. The rocket
named as SRP-5 will be launched inFairbanks, Alaska in Feburary 2005.

Figure 4. Observed MF radio wave intensity along the upgoing rocket trajectory (Left),
and the estimated electron number density shown by red line (Right).

.

Conferences
Conferences and Meetings ( July 2004 –October 2004)
1) The First Asia-Oceania Geophysics Society Meeting , Singapore, July 5-9, 2004
2) 35th COSPAR Scientific Assembly, Paris, France, July 8-25, 2004
3) NATO Advanced Study Institute on Sprites, Elves and Intense Lightning Discharges Corte inCorsica, July 21-30, 2004
4) The 28th Symposium on Space and Atmospheric Science in the Polar Regions, NIPR, Tokyo,
August 3-4, 2004
5) Western Pacific Geophysics Meeting : Honolulu Hawaii, August 16-20, 2004
6) AP-RASC'04, Qingdao, China, August 24-27, 2004
7) Society of Geomagnetism and Earth, Planetaqry and Space Sciences (SGEPSS), Ehime,September 26-29, 2004
8) 2004 STE Simulation Meetings, Chiba, October 28-29, 2004.
9) Pittsburgh, USA, November 6-12 2004.

Future Conferences and Meetings
1) AGU Fall meeting: December 13-17, San Francisco, 2004.
2) Space Weather/Climate Symposium #5, STEL, Nagoya, November 24-26, 2004.
3) Symposium on Space Environment, JAXA, Tsukuba, November 25-26, 2004.
4) AGU 2004 Fall Meeting, San Francisco U.S.A., December 13-17, 2004.
5) Third International Symposium on the Arctic Research and eventh Ny-Alesund ScientificSeminar, Tokyo, Japan, February 22-24, 2005
6) Magnetospheric ULF Waves (Chapman), San Diego, CA, USA, March 21-25, 2005
7) 7th International School/Symposium for Space Simulations, Kyoto, Japan, March 26-31, 2005
8) ISSS-7, Kyoto, March 26-31, 2005 http://www.rish.kyoto-u.ac.jp/isss7/9) 9th Spacecraft Charging Technology Conference, April 4-8, 2005,Tsukuba10) European Geosciences Union General Assembly , April 24-29, 2005, Vienna, Austria,2004
11) 9th Spacecraft Charging Technology Conference April 4-8, 2005, Tsukuba, Japan12) European Geosciences Union General Assembly 2005, Vienna, April 24-29, 2005
13) AGU 2005 Joint Assembly, Louisiana, USA, May 23-27, 2005
14) Asia Oceania Geosciences Society's 2nd Annual Meeting (AOGS 2005), June 20-24,
2005, Singaporean (http://www.asiaoceania-conference.org/)