Anomalous Electron Temperature Increases in the Evening Equatorial Ionosphere

Abstract

AbstractWe use novel radar observations at the Jicamarca Radio Observatory to study the first observations of highly enhanced plasma temperatures in the evening equatorial ionosphere. These short‐lived solstice evening events occurred following large upward plasma drifts and sharply reduced plasma densities. The electron temperatures increase during the August 5 and 6, 2011 moderate solar event reached peak values of about 1,000 K near 350 km. Smaller electron temperature increases were observed to altitudes up to about 500 km. There were also smaller concurrent ion temperature enhancements. During the very low solar flux January 20 and 21, 2020 event, a peak electron temperature increase of about 700 K occurred at an altitude of about 270 km. We also show that SAMI2‐PE simulations using the measured vertical plasma drifts reproduce the main characteristics of the measured plasma densities and temperatures up to 300 km, but not at higher altitudes. These simulations indicate that the evening anomalous plasma heating below about 300 km is due to the decrease in the electron‐ion cooling rate resulting from upward plasma drift driven decrease in the plasma density. Plasma transport and reduced cooling rate is a potential source of higher altitude heating.