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How to Look for Coronal Holes

Coronal holes are easy to spot in pictures taken of the sun using extreme ultraviolet light (EUV). In these pictures, coronal holes show up as dark spots, because the trapped hot gas that would normally emit EUV light has been blasted into space by the particles exiting through the coronal hole. (By the way, the bright spots are active regions, likely sites for solar flares .)

A coronal hole can persist for months or even years. As the sun turns on its axis (it makes one full rotation every 27 days), coronal holes come in and out of view. Only coronal holes near the sun’s equator—that is, holes pointing toward us—are likely to have effects here on earth.

Take a look at the current image of the sun below. Can you find any coronal holes? Are they toward the poles or near the equator, where they’re more likely to cause space weather?

Current Image of the sun from the 284Å Extreme Ultraviolet Imaging Telescope aboard NASA's SOHO satellite.



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