資料8-GCommission G Report
July 16, 2013
1. Research Report
1.1. Realtime ionospheric disturbance monitoring(Susumu Saito, Electronic Navigation Research Institute;
Takuya Tsugawa, National Institute of Information and Commnucations Technology)
Electronic Navigation Research Institute (ENRI) and National Institute of Information andCommunications Technology (NICT) developed a system to monitor ionospheric disturbances inrealtime. Observed data of 200 GPS receivers selected from the Japanese nationwide GPS reference
network (GEONET) are transferred to ENRI in realtime with a sampling rate of 1 Hz. The data areprocessed to produce a map of perturbation component of ionospheric total electron content (TEC)
every 5 minutes with a typical time delay of 1-2 minutes. The realtime monitor will be utilized in theJAXA/ISAS sounding rocket experiment for medium-scale traveling ionospheric disturbances tomonitor occurrence of the target phenomenon.
(http://www.enri.go.jp/cnspub/susaito/rocket/recent_mstid.html).
The two-dimensional maps of absolute TEC, rate of TEC change index (ROTI), and loss of lock on
GPS signals (LOL) are also available from NICT with 10-30 minutes delay(http://seg-web.nict.go.jp/GPS/RT_GEONET/index_e.html)
1.2 A new data format to promote international exchange and share of GNSS-TEC data
(Takuya Tsugawa, National Institute of Information and Commnucations Technology)
Several 100 km to 1,000 km scale ionospheric variations caused by equatorial plasma bubble and/or
travelling ionospheric disturbances can degrade single-frequency GNSS positioning and differential
GNSS positioning. However, these ionospheric disturbances have not been monitored enough due tothe lack of dense wide-coverage ionospheric observations. One of the most effective methods for suchdense and wide-coverage ionospheric observations is two-dimensional TEC observations using adense GNSS receiver network. Dense GNSS receiver networks are now available only limited areas
such as Japan, North America, and Europe. It is needed to expand the GNSS-TEC observation area
using all the available GNSS receiver networks with international collaboration of ionosphere andspace weather researchers in the world. We propose a new data format, GNSS-TEC Exchange format(GTEX), to promote international exchange and share of GNSS-TEC data. The main concept of theGTEX is to include slant TEC data from each GNSS receiver. By sharing slant TEC data which are
not converted to vertical TEC, various ionospheric studies may be possible without affected by
specific analysis procedures such as satellite/receiver bias estimation, or different mapping heights.
The structure of GTEX is designed to be as close to the format of GNSS observation data (RINEX) aspossible, because RINEX is a de facto standard in exchanging GNSS observation data and potential
users of GTEX would be familiar with RINEX. Since the 1st Asia-Oceania Space Weather Alliance(AOSWA) workshop held at Chiang Mai, Thailand during 22-24 February, 2012 (AOSWA, 2013), we
have collaborated with several organizations researching ionosphere and space weather in Korea,Thailand, Indonesia, Malaysia, and China to share the GTEX data of each country and to develop
dense wide-coverage TEC maps in the Asia-Oceania region. The GTEX has been adopted as the basisof ionospheric data sharing by Ionospheric Studies Task Force (ISTF) established in the Asia-PacificRegion of International Civil Aviation Organization (ICAO), which is working on ionosphericcharacterization for facilitation of GNSS implementation for aviation (ICAO/ISTF, 2012).

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Reference
Asia-Oceania Space Weather Alliance (AOSWA) (2013), http://aoswa.nict.go.jp/ICAO/ISTF (2012), Report of the second meeting of ionospheric studies task force (ISTF/2),
International Civil Aviation Organization Asia and Pacific Office, Bangkok, Thailand, October 2012,
http://www.bangkok.icao.int/cns/meeting.do?method=MeetingDetail&meeting_id=206
1.3. Airglow imaging experiment(Kazuo Shiokawa, Solar-Terrestrial Environmental Laboratory, Nagoya University)
The Solar-Terrestrial Environment Laboratory (STEL), Nagoya University is conducting variousoptical and radio measurements of ionosphere and thermosphere at 13 ground-based stations over theworld. The STEL have started new routine measurements of VLF/ELF waves at Athabasca (54.7°N,246.7°E), Canada since September 25, 2012, in collaboration with Kanazawa University andAthabasca University. STEL also started routine measurements of ionospheric airglow emssions at630-nm at Haleakala, Hawai (20.7°N, 203.7°E) in March 2013 in collaboration with Kyoto Universityand Tohoku University. These ground-based data are available from STEL web site.
Quick-look spectra are available at http://stdb2.stelab.nagoya-u.ac.jp/vlf/index.html
2. Meetings (future meetings)
Following meetings are scheduled in relation to URSI Commission-G.
IAGA the XIIth Scientific General Assembly, Merida Yucatan, Mexico, August 26-31, 2013
Symposium web-page: http://www.iaga2013.org.mx/
International CAWSES-II Symposium, Nagoya, Japan, November 18-22, 2013
Symposium web-page: http://www.stelab.nagoya-u.ac.jp/cawses2013/
Mesosphere, Thermosphere, Ionosphere Research Meeting,National Institute of Information and Communications Technology, Koganei, Japan,
September 16-17, 2013
3. Publication list
Thermosphere studies
H. Liu, T. Hirano, S. Watanabe, "Empirical model of the thermospheric mass density based on
CHAMP satellite observations", J. Geophys. Res., 118, 843-848, doi:10.1002/jgra50144, 2013a.
Liu, H. H. Jin, Miyoshi, Y., H. Fujiwara, H, Shinagawa, Upper atmosphere response to stratospheresudden warming: Local time and height dependence simulated by GAIA model, Geophys. Res. Lett.,
40, 635-640, doi:10.1002/grl.50146, 2013b.

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