On the Magnitude and Variability of Height Gradients in the Equatorial F Region Vertical Plasma Drifts

Abstract

AbstractPrevious radar studies have shown that magnitude of the vertical component of equatorial ionospheric E×B plasma drifts can vary significantly with height, even within main F region altitudes. These studies, however, were limited to few observation days. In order to properly quantify the height variation of equatorial F region vertical drifts, we examined 559 days of measurements made by the incoherent scatter radar of the Jicamarca Radio Observatory between the years of 1986 and 2017. From the observed profiles of vertical plasma drifts, we determined the mean behavior and variability of the height gradients as a function of local time and two distinct solar flux conditions (mean F10.7 around 80 and 150 SFU). Only observations made under geomagnetically quiet conditions were considered. Our results quantify the enhanced negative height gradients of vertical drifts near sunset that have been reported in the past. More importantly, we also identify and explain an enhancement in positive gradients near sunrise. We discuss the variability of the height gradients in vertical ionospheric E×B drifts at main equatorial F region heights, and the impact of this variability for satellite observations and studies of ionospheric stability and equatorial spread F.