資料7-GCommission G ReportAugust 6, 2014
1. Research Report
1.1. Report from National Institute of Communications and Information(Takuya Tsugawa, NICT)=== Report from recent papers ===After the M9.0 Tohoku-oki earthquake in 2011, strong deformation of ionogram echo traces, forming
multiple cusp signatures (MCS), were observed at three stations 790-1880 km from the epicenter. The
vertical structure of the ionospheric disturbances was determined by true height analysis and comparedwith broadband seismograph records at stations close to the ionosondes. These ionosphericdisturbances were caused by vertically propagating acoustic waves excited by the up/down groundmotion of seismic waves. Numerical simulations have shown that acoustic waves with a period of 1540 s and amplitude of order 1 mm/s at the ground level were sufficient to create MCSs. These acoustic
wave parameters are consistent with the seismic records if the motion of the air mass on the groundlevel is assumed to be the same as the ground motion. The travel time diagram of the seismic records
showed that the MCS ionogram first detected at each station was caused by P waves, while the otherswere caused by Rayleigh waves.
Reference
Maruyama, T., and H. Shinagawa (2014), Infrasonic sounds excited by seismic waves of the2011Tohoku-oki earthquake as visualized in ionograms, J. Geophys. Res. Space Physics, 119,4094?4108, doi:10.1002/2013JA019707.
1.2. Report from Solat-Terrestrial Environmental Laboratory, Nagoya University(Kazuo Shiokawa, Nagoya University)
Solar-Terrestrial Environment Laboratory, Nagoya University has kept optical observations of theionosphere and the thermosphere using the Optical Mesosphere Thermosphere Imagers at 13 stationsin Japan, Canada, Russia, Thailand, Indoensia, Norway, Australia, and Hawaii. The nighttime
medium-scale travelling ionospheric disturbance (MSTID) were statistically investigated using 630nm airglow images obtained at subtropical site Yonaguni (24.5N, 22 1E), Japan in collaboration with
the Electronic Navigation ResearchInstitute. The results show various characteristics of theequatorward boundary of the southwestward-moving MSTIDs at subtropical latitudes.
1.3. EISCAT Research Activities(Satonori Nozawa, Nagoya University)=== Report from recent papers ===(1) High-latitude ionospheric variations at times near auroral substorms exhibit large temporalvariations in both vertical and horizontal extents. Statistical analysis was made of data from theEISCAT UHF radar at Tromso, Norway, and International Monitor for Auroral Geomagnetic
Effects magnetometer, particularly focusing on the height dependencies. Results show clear
evidences of large electric field with corresponding frictional heating and Pedersen currents
located just outside the front of the poleward expanding aurora. At the beginning of the substorm
recovery phase, the ionospheric density had a large peak in the E region and a smaller peak in theF region.

資料7-G(2) We examined the brightness of 630.0 nm airglow, I630, associated with polar cap patches
observed during a magnetic storm that occurred on 22 January 2012. Brightness was measured
using an all-sky imager (ASI) located at Longyearbyen, Svalbard. The observed I630 wascompared with the F region electron density observed by the EISCAT Svalbard Radar (ESR). The
I630 was positively correlated with the F2 layer peak electron density, NmF2, and inverselycorrelated with the altitude of the F2layer peak electron density, hmF2, as expected from theknown relationship between these parameters. During the observation periods the measured
brightness frequently exceeded the calculated I630; we infer that in most cases, low-energy
particle precipitation is responsible for the extra brightness.
(3) A new solid-state sodium lidar installed at Ramfjordmoen, Tromso (69.6°N, 19.2°E), started
observations of neutral temperature together with sodium density in the mesosphere-lower
thermosphere (MLT) region on 1 October 2010. The new lidar provided temperature data with atime resolution of 10 min and with good quality between ?80 and ?105 km from October 2010 toMarch 2011. For the night of 5 October 2010, we succeeded in conducting simultaneous
observations of the new lidar and the European Incoherent Scatter UHF radar with the tristatic
Common Program 1 (CP-1) mode. Comparisons of neutral and ion temperatures showed a goodagreement at 104 km between 0050 and 0230 UT on 6 October 2010 when the electric fieldstrength was smaller, while significant deviations (up to ?25 K) are found at 107 km. We
evaluated contributions of Joule heating and electron-ion heat exchange, but derived values seemto be underestimated.
Reference(1) Oyama, S., Y. Miyoshi, K. Shiokawa, J. Kurihara, T. T. Tsuda, and B. J. Watkins, Heightdependent ionospheric variations in the vicinity of nightside poleward expanding aurora after
substorm onset, J. Geophys. Res., doi:10.1002/2013JA019704, 2014.
(2) Sakai, J., K. Hosokawa, S. Taguchi, Y. Ogawa, Storm-time enhancements of 630.0-nm airglow
associated with polar cap patches, J. Geophys. Res., doi:10.1029/2013JA019197, 2014.
(3) Nozawa, S., T. Kawahara, N. Saito, C. Hall, T. Tsuda, T. Kawabata, S. Wada, A. Brekke, T.
Takahashi, H. Fujiwara, Y. Ogawa, and R. Fujii, Variations of the neutral temperature and sodium
density between 80 and 107 km above Tromsoe during the winter of 2010-2011 by a new solidstate sodium LIDAR, J. Geophys. Res., doi:10.1029/2013JA019520, 2014.
2. Project progress
In March 2014, following research project was approved as one of 27 High-Priority Projects of theMaster Plan 2014 of the Science Council of Japan. In July 2014, the project was further listed in thedraft of Roadmap 2014 of Ministry of Education, Culture, Sports, Science and Technology (MEXT) as
one of 10 new plans. We appreciate strong support from the URSI community.
<Project outline>
Title: Study of coupling processes in the solar-terrestrial system
Project Summary: Energy from the sun is divided into radiation and solar wind (high-speedparticles), which are maximum at the equatorial and polar regions, respectively. We study the flowof the energy and materials in the whole atmosphere by establishing two large atmospheric radars
at these singular points, and global observation network.
Scientific Significance: We elucidate energy and plasma flow from the Sun to the Earth, responseof the Earth’s atmosphere, ionosphere and magnetosphere to short/long period variability of theSun, and coupling processes between these regions, which leads us quantitative understanding of
the solar-terrestrial environment as a whole system.

資料7-G

Social Value: The development of the new radar has direct impact on radio science, informatics
and electronics. Results from our studies will improve the forecast accuracy of severe weather andspace weather. Our plan will serve national and international capacity building through fieldstudies and international schools.
Period of the project: 2014 to 2024
Equipment of the project:(1) Equatorial MU Radar(2) EISCAT_3D Radar(3) Global observation network
PI and Institutions:
PI: Toshitaka Tsuda (RISH, Kyoto University)
Research Institute for Sustainable Humanosphere (RISH), Kyoto University
National Institute for Polar Research
Solar-Terrestrial Environment Laboratory, Nagoya University
International Center for Space Weather Science and Education, Kyushu University
IUGONET (Inter-university Upper atmosphere Global Observation NETwork)
consortium
3. Publication list
Publications were listed in each section of research report.