Magnificent sunspot 2192 produced a dramatic explosion on October 25th! After setting up my telescope and centering on 2192, the first image on my computer screen showed a huge flare erupting from the midst of the sunspot group! The flare was completely overexposed and white, as you can see in the first image below taken at 1:57 EDT (17:57 UT).
The flare diminished as time went on. At 3:06 EDT (19:06 UT), just 69 minutes after the first image was captured, the sunspot group looked like the next image. The overexposed white area had shrunk significantly.
The flare peaked at 1:09 EDT (17:09 UT) according to space weather websites. So my first observation was 48 minutes after the officially reported peak. The flare was diminishing at this time. If I had begun observing an hour sooner, I would have captured the rise of the flare toward its peak instead of its decline.
This was an X1 flare, the most powerful class of solar flares. Solar flares are classified according to their rate of energy output in X-rays. An X1 flare gushes energy at a rate greater than 0.0001 watts per square meter in X-ray wavelengths between 0.1 and 0.8 nanometers as measured by detectors in geosynchronous orbit around Earth. This 0.0001 watts may not seem like a lot of power per square meter, but this is the flux measured near Earth far away from the concentrated source on the Sun. By the time X-rays travel to Earth from the Sun they have spread out over a tremendous area. A square meter near Earth receives only 0.0001 watts, but at the source on the Sun energy is emitted at the rate of about 14 billion gigawatts!!! That's equivalent to the power output of 14 billion nuclear power plants!! It's a good thing we're so far from the Sun!
The next picture is a 22-image mosaic showing features spread over the solar disc. Sunspot 2192, with the white flare winding through its middle, is right of center. A very long dark filament runs horizontally above center. Modest sunspot 2194 is below center and sunspot 2195 is left of center. (Click on the image for a larger view.)
The immense dark filament stretching horizontally above the disc center is many, many times larger than Earth as shown in the next image where a comparison Earth is superimposed below the center of the filament. It may be hard to see the Earth image at first because, unfortunately, it seems to blend in with the background.
After collecting images for the disc mosaic above I thought the active sunspot might still be changing enough to make an interesting movie. So I recorded movie frames, one every 60 seconds, beginning at 3:08 EDT (19:08 UT). When 30 minutes had elapsed it seemed like nothing was happening, so I stopped recording at 3:38 EDT (19:38 UT). The 31-frame movie below shows the aftermath of the flare. At the beginning of the movie white areas are brightest. Over the next 30 minutes brightness diminishes as the flare continues to die down. The spot was perfectly positioned for making a long movie. I gave up too soon! Lots of details are changing within the sunspot group, although these changes weren't easily apparent as I captured video clips one by one. (Be patient while the movie loads. If it doesn't play automatically, click on it.)