Formation flying at night would be a specialised discipline.
It looks like something artificial like a searchlight equivalent well, well below the horizon, relatively close to the helicopters position. With the advancing (towards the ‘camera’) left side blade being higher than the ‘camera’ position the angle of attack would appear stronger so a reflection would have to be from a source of an equivalent angle on the trailing edge/more distant side of the more strongly angled blade. /— — I I
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