Midday auroral breakup events and related energy and momentum transfer from the magnetosheath

Combined observation by meridan scanning photometers, all-sky auroral TV camera and the EISCAT radar, permitted a detailed analysis of the temporal and spatial development of the midday auroral breakup phenomenon and the related ionospheric ion flow pattern within the 71o to 75o invariant latitude radar field of view. The observations reported are considered to be strong evidence of transient reconnection at the dayside magnetopause. Furthermore, the observed relationship between the optical signature and the ion drift observations is found to be consistent with a twin-vortex flow/current pattern in the ionosphere. The geomagnetic signatures are also in accord with this interpretation