Report on the Activity of Commission G

(8 March 2007)

1. Research activity

1.1 FORMOSAT-3/COSMIC observation campaign in December 2006

Research Institute for Sustainable Humanosphere (RISH) and Department of Geophysics, both Kyoto University, Solar-Terrestrial Environment Laboratory, Nagoya University, and Department of Geophysics, Tohoku University joined the FORMOSAT-3/COSMIC international observation campaign conducted on December 21, and 22, 2006. The purpose of this campaign was to validate ionospheric data from satellites with other observations. FORMOSAT-3/COSMIC is the constellation of six micro-satellites launched in April 2006. For the ionosphere, the satellites measure plasma density profile from GPS occultation experiment, and operate TIP (Tiny Ionospheric Photometer) and TBB (Tri-Band Beacon). We conducted following ground-based experiment for the campaign; IS and FAI observations with the MU radar, GPS-TEC measurement from the GEONET GPS receivers, airglow imaging from Rikubetsu, Shigaraki, Sata and Yonaguni. Collaborating with National Space Organization (NSPO) in Taiwan, we operated ISUAL on FORMOSAT-2 satellite in the special observation mode to measure 630 nm airglow layers in the F-region. Results from the campaign will be discussed in the next FORMOSAT-3/COSMIC workshop planned in Taiwan in May 2007.

1.2 Rocket experiment to investigate the electron-temperature enhancement at Sq focus

ISAS/JAXA successfully launched a sounding rocket S-310-37 on January 16, 2007 from Uchinoura Space Center (USC). The main purpose of this experiment was to reveal the electron-temperature enhancement near the Sq focus. By monitoring the location of the Sq current system by means of a ground-based network of magnetometers, the rocket was launched after the Sq focus was confirmed to exist near the trajectory. All instruments on the rocket worked fine, and successfully measured the electron density and temperature, electron energy distribution function, electric filed, and magnetic field. Quick-look of the data shows a clear high-temperature region near 100 km altitude.

1.3 3-D tomography of ionosphere over Japan based on GPS-TEC data

Tomography of ionospheric plasma density has been developed by Geophysics Institute, Kyoto University based on the GPS-TEC (Total Electron Content) data from the GEONET. The analysis is stable, and it is now possible to calculate 3D structures of the medium-scale traveling ionospheric disturbances (MS-TID) over Japan. An example of the analysis on July 27, 2004 is shown below. The left panel shows horizontal distribution of GPS-TEC drawn with the assumption of flat ionosphere at 300 km altitude. The right panel shows vertical distribution of the plasma along the red line in the left panel estimated by the tomography analysis. The ionosphere has clear height variation signifying the MS-TID.

1.4 Initial results of the Southeast Asian ionosonde network (SEALION)

Data from multi-point observation of the ionosphere at the equatorial and low-latitude stations (SEALION) revealed meridional structure of so-called F3 layer. Roles of the thermospheric wind and the zonal electric field on the formation of the F3 layer were examined through model calculations. Also SEALION was shown to have a great capability of studying ionosphere- thermosphere coupling process. Ionospheric height variations at the magnetic conjugate locations were used for inferring thermospheric neutral wind characteristics. The results exhibit a 6-hr periodic reversal of the transequatorial wind during nighttime, which might be related with the quarter-diurnal tide or the midnight temperature/pressure bulge. The asymmetry of the evening ionospheric heights at conjugate locations, and thus the strength of a transequatorial wind, was found to anticorrelate with onsets of equatorial spread F on an event-to-event basis, which confirms the transequatorial wind suppression mechanism for the Rayleigh-Taylor instability involving with the whole magnetic flux tube.

2. Past meetings

National meetings

12/8 4th Space Environment Information Users Forum (NICT., Koganei, Tokyo).

12/14,15 3rd Space Environment Symposium (Tsukuba Space Center, JAXA, Ibaraki).

12/21,22 Space Science Symposium (ISAS/JAXA, Sagamihara, Kanagawa).

12/22 Antarctica Syowa Base Large Atmospheric Radar Project (PANSY)Workshop

(NIPR, Itabashi, Tokyo).

12/25,26 JST・NICT Joint Simulation Workshop.

International meetings

1/3-6 Chapman Conference on Mid-latitude Ionospheric Dynamics and Disturbances

(Yosemite National Park, California, USA).

2/19,20 7th International Conference on Global Change: Connection to the Arctic (GCCA-7)

(Fairbanks, Alaska, USA).

3. Future Meetings

National meetings

3/8-9 CAWSES Space Weather Workshop (STEL, Nagoya U. Nagoya, Aichi).

3/28 STE Event Analysis Workshop (NICT, Kyushu U., Ehime U., Kyoto U.,Nagoya U./STEL; relayed via Internet）

International meetings

3/18-21 Workshop on Comparative Study of Space Weather and flare/Substorm

(Fairbanks, Alaska, USA).

3/20-23 International Symposium on Coupling Processes in the Equatorial Atmosphere

(Kyoto University Clock Tower Centennial Hall, Kyoto).

6/4-8 SuperDARN Workshop 2007 (Abashiri, Hokkaido)

7/2-13 IUGG/IAGA (Perugia, Italy).

7/30-8/4 AOGS2007 (Bangkok, Thailand).

8/20-24 2007 International Symposium on Antennas and Propagation (Niigata)

10/22-27 International CAWSES meeting (Kyoto)