Sun: Return of The Big Coronal Hole
At the end of October, a hole in the sun’s atmosphere lashed Earth’s magnetic field with solar wind, sparking moderately-strong geomagnetic storms and almost a full week of Arctic auroras.
News flash: It’s back. The same “coronal hole” is turning toward Earth again. NASA’s Solar Dynamics Observatory photographed the structure on Nov. 20th.
Coronal holes are regions in the sun’s atmosphere where the magnetic field peels back and allows solar wind to escape.
Since our last encounter with this hole in late October it has been transiting the farside of the sun, carried around by the sun’s 27-day rotation. Now that it is back we can see that the hole is not quite as large as it was a month ago–but it is still impressive, covering more than 1/4th of the visible solar disk.
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