Sensitivity studies of equatorial topside electron and ion temperatures

Abstract

Even in the recent extremely low solar minimum the electron and ion temperatures in the low‐latitude topside ionosphere display a great deal of day‐to‐day variability. This paper explores this variability using both the SAMI2 model and a newly developed steady state model of the plasma temperatures. Variations in the electric fields and neutral winds both produce drastic changes in the temperature profiles predicted above the magnetic equator. This implies that information about these parameters is contained in the temperature profiles measured at Jicamarca. Both winds and electric fields alter the arrangement of plasma throughout the entire low‐latitude ionosphere, including the locations and densities of the equatorial arcs. These changes have a much larger effect on the topside temperatures above the equator than changing the local advection or expansion alone because the topside equatorial temperatures are strongly coupled to the off‐equatorial F regions by field‐aligned thermal diffusion and photoelectron transport. The temperatures are more sensitive to changes in the nonlocal photoelectron heating than any other individual effect. The nonlocal photoelectron heating model used is still fairly primitive, however. The extreme sensitivity of the temperatures to the photoelectron transport model used means that more sophisticated photoelectron heating models will need to be used before meaningful comparisons between the model and observations can be made.