Sporadic E layer development and disruption at low latitudes by prompt penetration electric fields during magnetic storms

Abstract

An investigation of low‐latitude sporadic E layers during magnetic storms shows that the formation and disruption of these layers are strongly controlled by the magnetospheric electric fields that penetrate to equatorial ionosphere. It is observed that a prompt penetration electric field (PPEF) of westward polarity that dominates the nightside ionosphere can cause formation of sporadic E layers near 100 km, while a PPEF of eastward polarity that dominates the dayside and eveningside can lead to disruption of an Es layer in progress. It is shown that a vertical Hall electric field, induced by the primary zonal PPEF, in the presence of the storm‐associated enhanced conductivity of the night E layer, can be responsible for vertical ion velocity convergence sufficient to influence the Es layer formation. A downward polarity of the Hall electric field leads to Es layer formation, while an upward polarity causes the Es layer disruption. An interplay of magnetic storm associated prompt penetration electric field and energetic particle precipitation is evident in the observed Es layer response features in the region of the South Atlantic/American magnetic anomaly reported here.