Thermal electron measurement of the nighttime upper ionosphere by KOMPSAT-1 and comparison with the IRI

KOMPSAT-1 measured electron density and temperature of the pre-midnight upper ionosphere at 685 km altitude from June 28, 2000 to August 1, 2001. The data shows enhanced electron density compared to the IRI 2001 model during this solar maximum period along the magnetic equator, shifted toward the summer hemisphere. KOMPSAT-1 data also gives higher electron temperature in most of the low latitude regions than the IRI estimations. In general, KOMPSAT-1 measurements show more significant seasonal variations than the IRI model. It is seen that the longitudinal variation of the density and temperature distribution depends on the magnetic declination angle. Also, the KOMPSAT-1 data shows the solar activity dependence of the electron density and temperature with a time delay of two days.