Hey John, the way I deal with a thin bright halo uses the 'Darker Colour' blend mode in photoshop.
1) Open up you pic in photoshop. Duplicate the layer and change the blend mode from the default 'Normal' to 'Darker Colour.'
2) Highlight the move tool and then nudge the top layer to the left using the left arrow on your keyboard. After three or four clicks on the arrow the halo will dissapear because the 'Darker Colour' blend mode always allows the darker colour to show through. Since the halo is very light and bright it will not show. There will be other areas that have been affected so that you have a bit of a ghost like appearance but ignore that for now.
3) Add a layer mask to the top layer set to 'Hide All', all of the effects of the nudging of the top layer will now dissapear. Then all you have to do is select the paintbrush, set it to white, set it to a size a little bigger than the width of the halo and set the hardness to zero. Now just paint over the halo line and it will dissapear.
I have posted a 2 minute touch up of a screen shot of your pic. You will notice I also used the same technique to remove the less obvious halo on the left of the tree. I also removed the very slight haloing between the trunks where the light was just peeping through. In this case I cut and pasted a section from the grass area to the right of the tree onto the area between the trees. Again I set the blend mode to 'Darker Colour,' added a layer mask set to 'Hide All' and then painted away the halo.
Hope this helps
conkerwood