On possible interactions between upper and lower atmosphere

Comparison of geomagnetic data with data on tropospheric and stratospheric circulation characteristics shows a statistically highly significant shrinking in areal extent of the stratospheric vortex from the third to the eight day following a geomagnetic storm. During the contraction of the polar vortex edge, the mean height of the vortex central contour decreases only slightly. This indicates that a stratospheric warming event is associated with a steepening of the contour gradient rather than a warming over the entire area of the stratospheric polar vortex. The troposphere reacts to these weak, but nevertheless significant stratospheric warming events by a shrinkage of the area of the 500-mb cold air pool. It is shown that the observed warming of the stratosphere that follows a geomagnetically disturbed key day cannot be explained by simple radiation absorption.