Earth Planets Space, Vol. 54 (No. 12), pp. e13-e16, 2002E-LETTER
J. Ping1, Y. Kono1, K. Matsumoto1, Y. Otsuka2, A. Saito3, C. Shum4, K. Heki1, and N. Kawano1
1Earth Rotation Division, National Astronomical Observatory, 023-0861, Japan
2Solar-Terrestrial Environment Laboratory, Nagoya University, 464-8601, Japan
3Department of Geophysics, Graduate School of Science, Kyoto University, 606-8502, Japan
4Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, 43210, U.S.A.
(Received September 10, 2002; Revised November 14, 2002; Accepted December 6, 2002)
Based on the high time and spatial resolution total electron content (TEC) data, which is estimated from the phase and code observables obtained by using GPS (Global Positioning System) Earth Observation Network (GEONET), the TEC distribution and its time variation over Japanese Islands are scaled into 0.5° 0.5° grid data for each 10 minutes. The TEC daily map time series are arranged in an array to show the TEC evolution. Based on the spherical harmonics expansion of global ionospheric TEC model (GIM), which is estimated from global GPS observation, the TEC maps are expanded firstly through as high as 60 degrees and orders for a spherical harmonic function as a regional ionosphere map (RIM). The evolution history of medium scale traveling ionospheric disturbances (MSTIDs), i.e. polarward intense TEC enhancement and pre-noon rapid irregular fluctuations near the geomagnetic equator, are identified and confirmed in a quiet geomagnetic period.
key words: Ionosphere, GPS, TEC, global ionosphere map, regional ionosphere map.