Ionospheric Variations at Midlatitude Detected by a Dense GPS Receiver Array in Japan

Akinori Saito, Yuichi Otsuka, Takuya Tsugawa, Kazuaki Matsunaga, and Keisuke Hoshinoo

Abstract:	"Ionospheric variations over Japan were investigated with high spatial and temporal resolution data of GEONET, which consists of about 1,200 GPS receivers. Total Electron Content (TEC) data derived from GEONET clarified that various ionospheric phenomena cause the variation of the ionosphere in the region around 30 degrees of the geomagnetic latitude, and affect on the navigation system. The large day-to-day variation of TEC gradient over Japan was found to be attributed to the day-to-day variation of the Equatorial Ionization Anomaly (EIA) because Japan is located on the northern slope of EIA. The amplitude and location of EIA have large variability because they are controlled by a complex system among the neutral and the ionized atmospheres, lower and upper atmospheres, and low-latitude and high-latitude ionospheres. As a result, the variation of EIA is difficult to be predicted. Meso-scale ionospheric structures, such as medium-scale traveling ionospheric disturbances (MSTID) and plasma bubbles, drift in about 100m/s of velocity and cause variations of short temporal scale. They were often observed to be accompanied by smaller scale structures that generate phase and amplitude scintillations of the GPS radio waves. The activity of MSTID has maxima in summer and winter. During these maximum periods, they were detected by GEONET almost everyday. Plasma bubbles were detected in the lowest latitude area of Japan, and found to reach the central part of Japan in a few days in a year. Most of them were in the geomagnetically disturbed periods. The geomagnetic disturbances also generate large-scale traveling ionospheric disturbances and reduction of TEC."
Published in:	Proceedings of the 61st Annual Meeting of The Institute of Navigation (2005) June 27 - 29, 2005 Royal Sonesta Hotel Cambridge, MA
Pages:	425 - 428
Cite this article:	Saito, Akinori, Otsuka, Yuichi, Tsugawa, Takuya, Matsunaga, Kazuaki, Hoshinoo, Keisuke, "Ionospheric Variations at Midlatitude Detected by a Dense GPS Receiver Array in Japan," Proceedings of the 61st Annual Meeting of The Institute of Navigation (2005), Cambridge, MA, June 2005, pp. 425-428.
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