Diurnal variation of NmF2 associated with ExB drift at the equator during solar maxima

Abstract

The diurnal variation of peak electron density, NmF2, of five stations for different seasons, solar maximum conditions and quiet magnetic activity (Kp ≤ 3) is analyzed in terms of the ExB drift velocity at the equator. The stations analyzed are Kodaikanal at the magnetic equator, Tucuman and Okinawa at the crests of the equatorial ionization anomaly (EIA), and Yamagawa and Kokobunji at the outer sides of the EIA crests. The drift velocity was taken from an empirical model based on AE-E satellite measurements, and the meridional thermospheric wind from the HWM93 model. The departure of NmF2 from simple zenith angle dependence is qualitatively explained for stations at the magnetic equator and at the EIA crests based on the contribution of electrons coming from the equator. In the case of stations away from the EIA crests, NmF2 behavior follows mainly a zenith angle dependence, which is compared to the meridional wind pattern. In all cases there are features not explainable in terms of the ExB drift or the meridional neutral wind.