A
gigantic hole in the sun's atmosphere has opened up and a broad stream
of solar wind is flowing out of it. This is called a "coronal hole." It
is the deep blue-colored region in this extreme UV image from NASA's
Solar Dynamics Observatory:
Coronal
holes are places in the sun's atmosphere where the magnetic field
unfurls and allows solar wind to escape. In the image above, the sun's
magnetic field is traced by white curving lines. Outside the coronal
hole, those magnetic fields curve back on themselves, trapping solar
wind inside their loops. Inside the coronal hole, no such trapping
occurs. Solar wind plasma is free to fly away as indicated by the white
arrows.
For much of the next week, Earth's
environment in space will be dominated by winds flowing from this broad
hole. This should activate some beautiful Arctic auroras. NOAA
forecasters estimate a 65% of polar geomagnetic storms today as Earth
moves deeper into the solar wind stream.
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