Sunspot, and chance of weekend storms

The sun today, July 7, 2017. See the dark spot in the middle? It’s an actual hole in the sun’s outer atmosphere – a normal feature of the sun at solar minimum – what solar scientists call a coronal hole. Image via NASA SDO.

We’re approaching another minimum in the 11-year sunspot cycle, predicted for the years 2019 and 2020, and so the number of visible spots on the sun has been low. But there’s a nice, big, visible spot on the sun now, plus an Earth-facing coronal hole seen by spacecraft. Because this hole in the sun’s atmosphere faces Earth – and because it releases a high-speed solar wind – experts say there’s a 60% chance this weekend of minor G1-class geomagnetic storms, which could causes auroras. The coming full moon, of course, might interfere or might give you an opportunity for some interesting photos. The storms are expected on July 9, 2017 when the solar wind stream should hit Earth’s magnetic field.

The sun today, July 7, 2017. You can see the sunspot, which had just rotated into view along the sun’s limb, at about 9 o’clock in this image. Image via NASA SDO.
The sun today, July 7, 2017. Here’s today’s sun at yet another wavelength of light. See the sunspot in which, around 9 o’clock? And see the coronal hole? Image via NASA SDO.

As for the sunspot, it appeared on July 6 on the limb of the sun that had just rotated into view, and it was seen to grow rapidly. The animation below shows the sunspot over 36 hours:

Time-lapse over a 36-hour period beginning July 6, via NASA’s Solar Dynamics Observatory/

This sunspot should be an easy target for backyard telescopes equipped with solar filters. commented:

So far the sunspot has not produced any strong solar flares, but this could change if the sunspot’s breakneck growth destabilizes its magnetic field. Amateur astronomers are encouraged to monitor this expanding sunspot.

Of course, the sun is dynamic and changes rapidly, so be sure to check out NASA’s Solar Dynamics Observatory’s The Sun Now page for updates.

Another view of the coronal hole – or hole in the sun’s atmosphere – visible now on the sun. Image via NASA SDO.

Bottom line: There’s a visible spot on the sun now, and an Earth-facing coronal hole might produce some good auroras around July 9, 2017.

July 7, 2017

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Deborah Byrd

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