Equatorial evening prereversal vertical drift and spread F suppression by disturbance penetration electric fields

This paper presents new evidences on the responses of the evening sector equatorial ionosphere to prompt penetrating (PP) magnetospheric electric fields. In particular we show for the first time that the evening prereversal enhancement in the vertical drift/zonal electric field (PRE) and the consequent spread F (ESF) generation can be totally suppressed by penetration electric field of westward polarity arising from over‐shielding processes. In contrast the undershielding PP electric field of eastward polarity is found to enhance the PRE and ESF in agreement with recent findings. These results are evaluated using collisional interchange instability growth rate model calculations.