SOLAR SECTOR BOUNDARY CROSSING: Late on May 25th, Earth will cross a fold in the heliospheric current sheet and enter a region of space filled with negative polarity magnetic fields. Such fields can open a crack in Earth's magnetosphere, allowing solar wind to pour in and fuel geomagnetic disturbances.  According to NOAA forecasters, the odds of a G1-class storm is 20% to 30%. Aurora alerts: text, voice.

PHOTOGENIC SUNSPOT: Usually when a sunspot is really big, it is also really active. Not so for sunspot AR2546, a behemoth big enough to swallow Earth yet at the same time stubbornly quiet. Since it appeared 10 days ago, AR2546 has not unleashed a single significant solar flare. On the bright side, it's photogenic. Piotr Wieczorek sends this picture from Jantar, Poland:

"As the sun rose above the Gulf of Danzig on May 22nd, the morning clouds acted as a natural filter, allowing me to photograph this big sunspot," says Wieczorek. 

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