In response to the challenge of achieving reliable and repeatable ignition in scramjet combustors at low flight Mach numbers, this paper introduces a kerosene-air gliding arc plasma (GA_fa) igniter. Experimental investigations were conducted at a freestream total temperature of 900 K and a freestream velocity of Mach number 4, supplemented by Large Eddy Simulation (LES) to clarify the fundamental mechanisms of GA_fa-enhanced ignition in supersonic flows. Experiments on dual GA_fa igniter-assisted ignition under different Global Equivalence Ratios (GER) show that the GA_fa igniter significantly expands ignition limits compared to conventional high-energy spark igniters. The ignition process exhibits a critical GER threshold, leading to transitions among ignition failure, upstream cavity (C₁) stabilization, flame blowout, and downstream cavity (C₂) stabilization. Numerical simulations under pure-mixing conditions reveal that at low GER, insufficient Local Equivalence Ratios (LER) and poor kerosene atomization cause failure. As GER increases, C₁ achieves suitable LER first for ignition. At high GER, combustion-induced adverse pressure in C₂ prevents strong shock train formation upstream of C₁, while enhanced turbulence from C₁ promotes C₂ recirculation zone reactions, stabilizing the flame exclusively in C₂.