How can I create a solar flares effect using GIMP or Inkscape?
Something like this image:
Edit: first of all thanks for all the great comments and suggestions. My initial idea was to create the image based on real surface features of the sun, as seen in this image. My steps were
sun disk: create circle, create granule-like structure using GIMP's plasma effect, then perform desaturation, Gaussian filtering, colorization, and bloom effect
corona: copy sun disk layer and apply Gaussian filter with large radius (1/3 of image width maybe), overlay layer additively
transition region: in principle the same steps as for corona, but with a smaller Gaussian filter radius and added bloom
flares: for this step I did not have any good results, I tried some brushes, but nothing looked acceptable
Here is my intermediate result (without flares):
This looks like a composite of actual images of the sun from the SOHO solar observatory.
The sun itself is probably a single image and the prominences are probably hand-picked, rotated, and then placed. The "blown out" nature of the prominences adjacent to the sun's "edge" is probably caused by the individual layers being set to a blend mode such as "lighten."
A large portion of NASA's imagery data is "open-source" in a sense, at least the RAW unprocessed type may be. Most of their imagery is actually greyscale taken at a specific wavelength or narrow wavelength band and the colors are simulated. Even for the "real-color" versions.