Hot spot generation by Lower Hybrid (LH) launchers is found to be governed by a resonance in the plasma electric field response to the external drive. The kinetic analysis in 1D-1V in the parallel direction allows one to compute the amplification effect for small amplitude of the external drive. The resonant Lorentzian response distorts the distribution function with an island structure in the suprathermal part at the phase velocity of the external electrostatic drive. The non-linear features enhance the plasma response driving overlap effects between multiple waves at rather low amplitude. The onset of a plateau in the distribution function with extent up to one thermal velocity is already obtained when the standard overlap condition is achieved. The sensitivity of the resonance to plasma parameters and large variation of the amplification magnitude can compensate the fast radial decay of 1