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Astro Bob

Minimalist Sun May Stoke Aurora Tonight

23 Jul 2018, 17:42 UTC
Minimalist Sun May Stoke Aurora Tonight
(200 words excerpt, click title or image to see full post)

Today’s sun is blank like it’s been for much of 2018 as the solar cycle heads toward a 2019-2020 minimum. The fine texture you see is caused by solar granules which are the tops of rising cells of hot plasma. A typical granule is about 1,500 km across and lasts around 10 minutes before cooling and sinking back into the sun. NASA / SDO
It’s been a long time but skywatchers in the northern U.S. states have a shot at seeing the aurora beginning at nightfall tonight through about 1 a.m. (Central Time). We’ve been in a dry spell for northern lights for some time now. That’s not surprising considering that the sun is slouching toward the next solar minimum expected in 2019-2020.
Graph showing the last three solar cycle plotting sunspot numbers. The double peak of the current cycle is shown. You can see there’s been a general decline in solar activity over the past 25 years or so. NASA
Solar activity bounces back and forth between high and low during a cycle that lasts about 11 years. The last maximum occurred in spring 2014 and was one of the wimpiest on record. In fact, it was the least ...

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