Space weather opening a crack in our planet's magnetic defenses.

Sometimes the sky surprises us. On Feb. 14-15, with little warning, geomagnetic activity rippled around the Arctic Circle, producing an outbreak of auroras that veteran observers said was among the best in months. At the height of the display, a US Defense Meteorological Program satellite photographed a whirlpool of Northern Lights just north of the Bering Sea:



"A number of images from the DMSP F18 satellite captured the dramatic auroral event of the last couple nights," says analyst Paul McCrone, who processed processed the data at the US Navy's Fleet Numerical Meteorology and Oceanography Center in Monterey, CA.

The reason for the outburst is still not completely clear. It got started on Feb. 14th when a magnetic disturbance rippled around the Arctic Circle. No CME was obvious in local solar wind data at the time; the disturbance just ... happened. Once begun, the disturbance was amplified by the actions of the interplanetary magnetic field (IMF) near Earth. The IMF tipped south, opening a crack in our planet's magnetic defenses. Solar wind poured in and fueled the auroras.

[link to www.spaceweather.com]