The role of magnetospheric electric fields in producing auroral zone thin layers

Abstract

Numerical simulations have been used to examine the thickness and altitude of thin metallic ion layers which could be produced by the strong magnetospheric electric fields which map down into the auroral-zone ionosphere. Field directions between northward, through westward and southward to south-eastward are found to be able to produce layers (northern hemisphere). Observations of thin layers made with the EISCAT radar (69.6° N, 19.2° E) are also described, together with simultaneous measurements of electric fields and E-region ion-drifts. The layers are found to be most often correlated with the presence of electric fields directed between westward, through southward, to south-eastward and are largely consistent with simulations. However, some extra mechanism is required to explain the absence of intense layers for field directions between north and west and the extreme thinness of the layers in some cases. Correlated sudden sodium layers have been observed in some cases and a mechanism involving interaction with dust particles is proposed to account for the appearance of both the sodium atoms and additional metallic ions.