This MUST be a photo-composite, IMHO:

1: intensity differnces between the solar disk and the backlighted trees are unexpected.

2: The location of the true rising sun is to the right of the image - there may even be a hint of the true disk of the sun, but this is probably just a sliver of the real sun.

3: If the sun were really this low to the horizon on a telephoto shot, it's shape would be dramatically distorted to non-circular by atmospheric refraction.

4: The "dark edge" to the sun is a dead giveaway that that part of the image is clipped from a detailed solar image anf pasted behind the treeline.

All said, though, it's a beautiful picture!