TEC derived from incoherent scatter measurements during solar maximum and their comparison with IRI-2001 model

Abstract

The diurnal and seasonal variations of the total electron content (TEC), derived from high resolution electron density profiles measured with the Arecibo (18.4°N, 66.7°W, dip 50^oN) incoherent scatter radar, are examined during high sunspot activity period (1989-90). Median values of TEC are then obtained at each hour during different seasons and compared with those obtained from the latest available International Reference Ionosphere (IRI-2001) model. The diurnal variations of TEC show more or less similar trend during all the seasons (i.e. maximum around daytime and minimum around midnight) with the largest values of TEC during equinox. The variability of TEC is larger at night than by day during all the seasons. Comparison of the diurnal variation of the observed median values of TEC with those predicted by the IRI model reveals, in general, similar trend during all the seasons and at all local times except during winter, when the IRI exhibits diurnal peak of TEC at around 0900 hrs LT, and the observed median peak occurs at around 1400 hrs LT. Discrepancies between the IRI and the median values exceed 40% during nighttime for winter and equinox. However, during daytime, they are less than 20% for all the seasons, except w inter morning hours. The TEC peak content increases by a factor of around 4 from solar minimum (1975-1 976) to solar maximum (1989-1990).