Pic takes FOREVER to load!

What you’re looking at is the radiance of the comet core (the glaring bit inside the coma), and the bow shock (the almost-lavender colored C-shape that appears to be in front of [though actually beside] the nucleus) of the ion tail itself. The day side of the comet is receiving the brunt of the sunlight (go figure), and the Solar wind is striking heaviest here. This is the hottest point of the ion cloud. From here back, the cloud spreads, is pushed away from the Sun, and cools.

Like the wake of a ship in the ocean -- or more precisely a stone projecting from a flowing stream (as you posted here) -- the wind meets the instigating bow shock, or bow wave, of the stone and is forced to either side of the obstruction, in this case the comet nucleus, raking with it the ionized particles released in the outgassing process, resulting in the familiar V of the ion tail. The tail will naturally appear brighter along the outer edges of the V, because this is a 3D object in 3D space, so, and as with an airborne bubble, the sides appear to be more dense. They aren’t. You can walk all the way around the bubble and see no difference.

In this tight image, though, the tail is particularly drowned out, due to the commanding brilliance of the nucleus’ albedo (note as well the absence of stars).

Dan