| Co-Investigator(Kenkyū-buntansha) |
NOZAWA Satonori Nagoya University, Solar-Terrestrial Environment Laboratory, Associate Professor (60212130)
OTSUKA Yuichi Nagoya University, Salar-Terrestrial Environment Labaratary, Assistant Professor (40314025)
FUJIKI Ken'ichi Nagoya University, Solar-Terrestrial Environment Laboratory, Assistant Professor (20303597)
増田 智 名古屋大学, 太陽地球環境研究所, 助教授 (10262916)
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| Budget Amount *help |
¥2,580,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥180,000)
Fiscal Year 2007: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2006: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2005: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
In this research, we tried to reveal response of the ionosphere to solar activity based on observations. This research has the following four steps; (1) constitution of the database on solar flare X-rays data and EUV irradiance data, (2) observational studies on characteristics of solar flares, (3) development of the method of EUV data analysis and data analysis itself and (4) observational studies on increase of total numbers of electrons (so-called TEC) in the ionosphere due to solar flares. As for the step (1), we made a 10-year catalogue/database for solar flares observed with Yohkoh, including the information of X-ray light curves and flare images. By using this catalogue, we analyzed solar flares statistically for the next step (2). Then, we estimated the density of the solar atmosphere where hard X-rays are emitted. It is also shown that the density depends on energy of the X-ray photons. In the step (3), we developed a new method which estimates EUV flux from soft X-ray flux during solar flares. Because the time resolution is very bad while soft X-ray data are taken continuously. Thanks to this method, we can get virtual EUV flux data any time. In addition to this, we compared EUV flux, F10.7 index, tar (total solar irradiance), and soft X-ray data Then we hard that F10.7 index correlates EUV flux, but can not be used for In the final step (4), we compared zenith angle of the sun, flare intensity, and TEC statistically and revealed that increase of TEC linearly correlated EUV flux from solar flares. The good correlation between TEC derived inn GPS data and EUV flux, indicates that the F-layer of the ionosphere could affect GPS signals. Finally, we found an asymmetry of TEC variations bath in the summer and winter hemispheres. This result suggests that the ionospheric response to EUV flux variations depends on the background condition of the atmosphere
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