Simulations of the equatorial thermosphere anomaly: Physical mechanisms for crest formation

Instead, we found that the formation of the ETA crests is attributed to plasma-neutral heating which has two peaks in the topside ionosphere aside the magnetic equator. These two peaks, which are largely controlled by the magnetic field, are the results of energy transfer from thermal electrons and ions to the neutrals through collisions due to their temperature differences, albeit the ultimate source of this heating is solar radiation which produces photoelectrons that mainly depend on solar zenith angle.

The TIEGCM simulations show that the crests of the ETA always locate poleward by 10°–15° with respect to those of the Equatorial Ionosphere Anomaly (EIA), although the trough location of the ETA resembles that of the EIA. The location of the ETA crests is associated with the two-hump structure in plasma-neutral collision heating which is small inside the EIA region and larger at the poleward edge of this region.