We examine the Earth's ionospheric response on May 11, 1999, to an unusually tenuous solar wind, focusing on magnetometer, riometer, and optical data from high geomagnetic latitudes in Antarctica. Comparisons are also made with POLAR satellite data during a perigee pass over Antarctica, and with geomagnetic data collected at low latitudes. It is shown that the southern hemisphere was geophysically active, even though the Kp index on May 11 ranged only from 0 to 0+. Furthermore, despite the fact that the IMF and solar wind conditions favored northern hemisphere polar rain, low energy electron precipitation did occur in the southern polar cap. Geomagnetic power levels at low, cusp, and polar cap latitudes were also lower on May 11 than on surrounding days. Although this might be expected, discrete millihertz peaks in ULF power were still evident, especially at cusp latitudes. ¿ 2000 American Geophysical Union