Drag force reduction is well known effect of the interaction of microwave filament and aerodynamic body in supersonic flow [1, 2]. Some recent experiments showed the possibility of drag force enhancement as the result of the interaction, too [3, 4]. The enhancement has been registered for limited filament length in particular cases of asymmetrical filament location. In this paper the mechanism of drag force enhancement for asymmetrically located filament is established. The mechanism is shown to connect with forming the "heat piston" in front of the body inside a shock layer. This phenomenon is investigated for wide class of defining flow parameters: rarefaction degree in the filament, impulse time duration and filament location relatively the body.