For months, it was “Eclipse!  Eclipse!”  Then, that abruptly ended.  Well, the sun is apparently jealous of the sudden lack of attention, as this week it reached out and smacked the Earth with a large coronal mass ejection (CME) as if to say, “Hey!  Still here!”

NASA's_SDO_Observes_Largest_Sunspot_of_the_Solar_Cycle_(15430820129)So let’s pay attention – fortunately, all those eclipse-viewing glasses are still useful.  If they’re still in good shape, not torn or anything, use them to take a look at the daytime sun.  This week (as originally pointed out to me by friend-and-follower, Tom) there were sunspots large enough to EASILY see with the naked eye and eclipse glasses.  This was the same spot grouping ultimately responsible for the big flare back on Thursday (Sept 7).  That group is now about to rotate beyond the western limb and onto the far side of the sun for the next 2 weeks.  They may or may not be there when that spot on the Sun’s surface rotates back into view.

The stream of ionized material from CMEs poses some danger to satellites, high-altitude aircraft, and even Earth-based communications systems – but interaction between these particles and Earth’s magnetic field also creates auroras, and we’ve had some nice ones for the past few days, visible down into the continental US through the midwest.  Hopefully some of my readers were able to get a glimpse?  Let me know!  Acadia National Park posted a great shot on their Instagram feed of the aurora over Jordan Pond – it was the exact same view, except with a lightshow, that I had a month ago.  (Unfortunately I can’t link or share that directly here – but check out acadianps on Instagram…) Seeing them this far south is unusual in any case, but particularly in the summertime.  Spaceweather.com is an excellent site for aurora prediction and other observations on sunspot activity, CMEs, cosmic ray intensity, and the like.  It includes a nice graphic of the auroral coverage on a global view, making me jealous of Alaskans’ frequent viewing opportunities!

Sunspots are dark because they are aligned with concentrations of magnetic flux in the solar magnetic field.  These flux lines reduce convection at the solar surface, resulting in areas that are relatively cool (not, by any means, cool in absolute terms.  They’re absolutely still incredibly hot, but compared to the normal surface, they’re cooler and darker).  They normally occur in pairs, with opposite magnetic polarity, and this creates loops in the magnetic field lines – from one spot to the other – that pulls plasma up and into large loops and prominences off the surface.  These things are HUGE – a typical prominence is about ten times the size of the Earth, and the biggest are of course much larger.  Occasionally, as the magnetic field twists and changes, these loops snap, whip-like, and fling large amounts of matter into space.  This is a coronal mass ejection, and when they come at Earth, like they did this week, “space weather” happens.

Sunspots_on_sunSolar activity tends to peak on an 11-year cycle, and we’re actually headed toward a minimum (with the lowest point projected in 2020).  But the activity this week reminds us that this is a statistical cycle, and that these things can happen at any time.

All in all, these are very violent events.  The Sun is a crazy, impressively dynamic beast, constantly changing – even though it appears to be a boring old ball of gas.  Very fortunately for us, the Earth’s magnetic field and ozone layer shield us from the Sun’s fury, and make these things beautiful and interesting, instead of deadly!  Put those eclipse glasses to use and see what you can see!

Get Out There
Troy
flying-squirrel.org

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