Weekend Auroras

Weekend Auroras

A fast-moving stream of solar wind expected to hit Earth's magnetic field over the weekend ... did not. Bright auroras appeared anyway. "The the whole sky exploded," reports Truls Tiller, who saw this "big corona" on March 28th while camping outside the village of Skibotn, Norway:

What caused this display? On March 28th, the interplanetary magnetic field (IMF) near Earth tipped south, opening a 'crack' in our planet's magnetosphere. The fast solar wind had not yet arrived. Even so, there was plenty of slow solar wind in the area to flow through the crack and fuel the outburst.
NOAA forecasters believe the tardy stream of solar wind is still coming. When it arrives, possibly on March 30th or 31st, the solar wind speed around Earth will surge from ~300 km/s (slow) to ~700 km/s (fast). The increase could spark even brighter lights than the ones Tiller saw. High-latitude sky watchers should remain alert for auroras as the new week begins.

From SpaceWeather.com