The correlation between Solar EUV Flux and Plasma Characteristics in the Low-Latitude Topside Ionosphere at Nighttime

We present the results of the correlation between solar EUV flux and ionospheric plasma parameters observed by KOMPSAT-1(685Km altitude, 2250 local time) and DMSP F-15(840Km altitude, 2130 local time) in the low-latitude topside ionosphere. The plasma density and temperature observed by KOMPSAT-1 and DMSP F-15 from June 28, 2000 to August 1, 2001 were analyzed with F10.7 which is a standard proxy for solar EUV flux. Especially, the data of the geomagnetic latitude between -60ør"¡ and 60ør"¡ in the nighttime were considered at the low- and mid-latitude region. From the result, it was shown that the plasma density and temperature at local maximum density region in the geomagnetic equator were increased with F10.7. Furthermore, the best correlation between F10.7 with a lag of 2 days and plasma parameters was observed. It means that the ionospheric equatorial plasma is influenced by the solar EUV flux with the delay of 2 days.