AURORA SURPRISE: A stream of solar wind hit Earth on Jan. 25th. The impact sparked an unexpected G1-class geomagnetic storm. "Suddenly, the whole sky was moving and dancing. It felt like aurora was hitting us with a hammer onto the head," reports Markus Varik, who sends this picture from Tromsø, Norway:

https://imgur.com/ejRYq52

"For a moment, local magnetometers dipped down to more than -1000 nT!" says Varik. "A significant magnetic disturbance was underway, and the auroras were visible despite bright moonlight."

The solar wind was expected. It emerged from a small hole in the sun's atmosphere, which forecasters had been tracking for days. The surprise occurred when a crack formed in Earth's magnetic field. Solar wind poured in, fueling a storm in disproportion to the size of the stream.

"That," says Varik, "was a pleasant surprise."

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