Irregular magnetic pulsations in the polar cleft caused by traveling ionospheric convection vortices

Abstract

Irregular magnetic pulsations with periods of 5–8 minutes analyzed using data from an array of temporary stations around Sondre Stromfjord, Greenland have been found to correspond to traveling convection vortices. The vortices can be sorted into different classes corresponding to the following types: 1) isolated twin vortices, 2) single vortices and 3) multiple vortices. The vortices are observed in the pre-noon sector as well in the post-noon sector although more frequently in the pre-noon sector. The motion is generally antisunward along the auroral oval. Although magnetic variations like those discussed here have been proposed to be ionospheric signatures of flux transfer events (FTE's) the spatial and temporal resolution of the Greenland magnetometer observations show that none of the observed vortices may be explained by existing models of flux transfer events.