Coronal holes are large regions in the corona that are less dense and cooler than surrounding areas. The open structure of their
magnetic field allows a constant flow of high-density
plasma to stream out of the holes. There is an increase in the intensity of the
solar wind effects on Earth when a coronal hole faces us.
The x-ray image above shows the Sun as viewed by the Yohkoh satellite. A large coronal hole, extending from the northern into the southern solar hemisphere is near the Sun's center. The brightest region shows hot loops that remain after a solar flare.
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