STORM WARNING: A fast-moving stream of solar wind is buffeting Earth's magnetic field. The combined effect of this stream plus a CME expected to arrive soon (see below) has prompted NOAA forecasters to declare a 30% to 35% chance of geomagnetic storms on June 23-24. High-latitude sky watchers should be alert for auroras.
CME FORECAST, REVISED: A CME propelled toward Earth by the "solstice solar flare" of June 21st may be moving slower than originally thought. Analysts at the GSFC Space Weather Lab have downgraded the cloud's probable speed from 800 km/s to 650 km/s. Impact is now expected on June 24th at 0700 UT plus or minus 7 hours. In this animated forecast model, the yellow dot is Earth:
A slower CME should deliver a weaker blow to Earth's magnetic field. Forecasters now predict a relatively mild G1-class (Kp=5) geomagnetic storm when the cloud arrives. High-latitude sky watchers should be alert for auroras during the early hours of June 24. The season favors observers in the southern hemisphere
http://www.spaceweather.com/