Spots when light on and smoke squares. Causes?

[Alexandr Zlotsky 1]

On small and medium rps of the engine, when the landing lights are switched on, during the movement of the aircraft, dark spots appear, emanating from the headlights and chaotically moving ahead of the headlights. When the airplane with the headlights on does not move, the spots disappear. Give a link on this issue, if anyone knows any causes, please. I do not read English well, so it's hard for me to find this topic on the forum. Thanks.