venerdì 21 aprile 2017

POTENT CORONAL HOLE TURNS TOWARD EARTH: A large hole in the sun's atmosphere is turning toward Earth, and it is spewing a stream of fast-moving solar wind toward our planet. NASA's Solar Dynamics Observatory photographed the giant fissure on April 21st:


This is a "coronal hole" (CH) -- a vast region where the sun's magnetic field opens up and allows solar wind to escape. Gaseous material flowing from this coronal hole is expected to reach our planet on April 23rd or 24th and could spark moderately-strong G2-class geomagnetic storms. NOAA forecasters say the odds of a magnetic storm is 75%.

We've seen this coronal hole before. On March 27th it lashed Earth's magnetic field with a fast-moving stream that ignited intense auroras around both of Earth's poles. The coronal hole is potent because it is spewing solar wind threaded with "negative polarity" magnetic fields. Such fields do a good job connecting to Earth's magnetosphere and energizing geomagnetic storms. Free: Aurora Alerts

spaceweather.com

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