I was going to keep its secret but what he hell .
I drew some 1 px line with a bright color in the direction of the sigs flow , then i applied Filter > Distort > Ripple on small seting on 999 amount , then i hit Ctrl + f to do it again , and then set to hu duplicated and gfasin blured the set to lighten then merged those 2 layers and set to color dodge
@ Biggles , i forgot to mentiob , buti though you would realise , dont leave the gradien map on normal or 100 % transparency