Wind‐shear‐driven, closed‐current dynamos in midlatitude sporadic E

Rocket and radar experiments have found anomalously large electric fields associated with midlatitude sporadic E ( E s ). In Cosgrove and Tsunoda [2001], a neutral wind source mechanism for the electric fields was proposed, by way of a simple model involving two idealized E s patch dynamos closing current with one another. Below, we show that this source mechanism can operate in generic distortions or fragmentations of an E s layer. The result is a closed‐current dynamo phenomenon that occurs whenever a E s layer is distorted against a wind shear background. Either modulation of the E s layer altitude by a gravity wave, or Kelvin‐Helmholtz billows, could produce large electric fields.