Solar Flare

Lucky Timing

On July 3rd it had been more than two months since my last solar imaging session. Conditions were unusually nice for a July morning! Humidity was low, skies were clear, a modest breeze blew away annoying insects, and temperature ranged in the low 70's. Summer mornings in Williamsburg are rarely clear and clouds inevitably increase near noon. By 11:00 AM clouds put an end to my observing opportunity. The satellite view below shows the temporary clear viewing window for southeastern Virginia. One major sunspot and a few filaments appeared on the Sun's disc as you can see in the next full-disc mosaic constructed from 21 individual panels.

Sunspot 2835 appears on the right in the Sun's southern hemisphere. It is accompanied by three floating filaments. In center, above the equator is an active area numbered 2837. Also in the northern hemisphere, on the right, near the limb, is a filament. To this filament's right, almost on the rim itself is sunspot 2838 just before emitting a flare. (Click on the image to get a larger view with better detail.) 

The previous mosaic was processed to show details on the disc so rim details are not visible. The next mosaic was processed to show prominences and spicules around the rim.When the previous disc mosaic is inverted positive to negative, the floating nature of the filaments becomes more apparent. Once again, you should enlarge these images to see the best detail.

I used my Hinode solar guider while capturing all individual images here. It prevented image drift caused by imperfect tracking. Let's take a closer look at some features. Active area 2837 did not display a visible sunspot umbra, but you can see white areas of higher energy emission around the slightly disturbed surface. 

Large sunspot 2835 was better placed near center on the solar disc a few days earlier. On July 3rd 2835 was diminishing, approaching the western limb, and soon to rotate out of sight. A white area of energetic emission is left of the umbra. A nice prominence sat on the limb nearby. I had to combine two images to make the prominence visible. The image showing sunspot detail did not show the prominence. The image showing the prominence overexposed the sunspot. Combining the images makes a nice scene.

Now we come to the solar flare! The explosion happened in a small, relatively inconspicuous developing sunspot numbered 2838 very close to the northwestern limb. In the next image, captured before the flare at 9:58 AM EDT, sunspot 2838 is a small white area on the Sun's limb to the lower right of the dark filament. 

Things had changed 36 minutes after the previous image was obtained! When I returned to get another image at 10:35 AM EDT, I saw an extremely bright overexposed area bursting out of the sunspot! Sometimes the timing is lucky!

Although the small eruption doesn't look very dramatic, it was the most powerful solar flare observed in four years! It caused magnetic field fluctuations on Earth and a shortwave radio blackout over the Atlantic Ocean. Flare strength is described on a scale that measures x-ray brightness. The flare above was classed as an X1.5 flare, at the lower end of the most powerful type. It's always a surprise to see rapid change on the Sun in real time! The flare was extremely bright on my laptop screen.