Thursday, June 15, 2017

Sun's large Coronal Hole to Face Earth

A large hole has opened in the sun's atmosphere and it is turning toward Earth. NASA's Solar Dynamics Observatory is monitoring the structure, shown here in an extreme ultraviolet image taken on June 13th:This is a coronal hole (CH) -- a region where the sun's magnetic field peels back and allows solar wind to escape. A fast-moving stream of solar wind from this coronal hole is expected to arrive on June 16th, possibly sparking G1-class geomagnetic storms. High-latitude sky watchers should be alert for auroras, especially in the southern hemisphere where autumn darkness favors visibility.

Forecasters note that this stream is unusually fast with wind speeds as high as 700 km/s. Moreover, it is threaded with "negative polarity" (south-pointing) magnetic fields. Such fields do a good job connecting to Earth's magnetosphere and energizing geomagnetic storms

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