speed: 633.0 km/sec
A fast-moving (~600 km/s) stream of solar wind is buffeting Earth's magnetic field this weekend. Reports of high-latitude auroras are few, however, because of the nearly full Moon and midnight sun around the Arctic Circle. NOAA forecasters estimate a 40% chance of polar geomagnetic storms on June 22nd.
SOLSTICE FULL MOON: This weekend's full Moon is a "supermoon," as much as 14% bigger and 30% brighter than other full Moons of 2013. Even on Friday night, 36 hours before maximum illumination, the Moon already looked super:
SOLSTICE SOLAR FLARE: The northern summer solstice began with a bang. On June 21st at 03:16 UT, sunspot AR1777 produced a long-duration M2-class solar flare. NASA's Solar Dynamics Observatory photographed the flare's extreme ultraviolet flash and a plume of material flying out of the blast site: