Gradient drift irregularities in mid‐latitude sporadic E

Three‐meter E region irregularities observed by a portable 50‐MHz radar on the island of Guadeloupe in June 1977 are shown to have the same properties as 3‐m irregularities generated by the gradient drift instability at the equator and in the auroral zones. The irregularities occur when intense sporadic E patches are known to occur, suggesting that they are generated by the gradient drift instability acting on the large vertical gradients in sporadic E patches. Large, rapid E region drift variations observed on two occasions suggest either that the E region electric fields are structured and less than 450 km in horizontal extent, or that E and F region fields couple and decouple intermittently during ionospheric sunset.