Mini map changes

I don’t mean fog of war. I mean when playing as Protoss there are white streaks starting at the right of the minimap and diminishing as they go leftward. I used “black sheep wall” to really get a good look at it and if I could upload the screenshot I can show you.

Normally if you hit tab you just see a black minimap and other units, what are those white streaks in the Protoss missions?