We use the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure to produce composite maps of high-latitude ionospheric parameters for 11 May 1999. On that day there was a near void in the solar wind momentum flux. Yet, focused high-latitude interactions occurred at Earth. Our maps of convection, Joule heating, particle precipitating power and field-aligned current show a striking asymmetry between hemispheres. In the latter three parameters there is at least a five-fold difference in values between the hemispheres. The northern hemisphere polar cap particle precipitation is the strongest we have ever mapped. Strong electrodynamic interactions were focused above 70¿ north magnetic latitude. In the southern hemisphere only weak, irregular patterns are mapped. We attribute these differences to the strong interplanetary magnetic field spiral configuration, the sunward tilt of the northern hemisphere and the direct beam or strahl of solar electrons impinging on the northern polar cap during the momentum void. ¿ 2000 American Geophysical Union