Plasma Bullet as a Plasma Diffusion Wave-Packet in Plasma Jets

The propagation of a plasma bullet in a plasma jet is described under the base of plasma fluid theory in terms of the plasma drift, the gas flow, and the plasma diffusion. The analysis reveals that the plasma bullet originates from the electrostatic diffusion wave in plasma propagating in the plasma column of jets. The plasma diffusion waves, electron waves, and ion waves propagate in the form of a wave-packet modulated by the operation frequency of the voltage pulse. The waves have the dispersion relation of omega similar to ku(alpha phi), and the wavelength has the order of Debye length lambda(D) similar to 10(-4) m as k(2) lambda(2)(D) similar to 1. The phase velocity is u(alpha phi) similar to(u(alpha d) + u(b) + u(n) + kappa(alpha)u(n)) with the mobility ratio of kappa(e) = vertical bar mu(e)/mu(i)vertical bar for electrons (alpha = e) and kappa(i) = 1 for ions (alpha = i). The terms u(ed), u(id), u(b), and u(n) represent the electron drift velocity, the ion drift velocity, the gas blowing velocity, and the plasma diffusion velocity, respectively. The waves are modulated to be the wave-packet of d omega similar to u(g)dk with the group velocity of u(g) similar to c(s)(2)/u(n)similar to(10(4)-10(5)) m/s, where the acoustic velocity is c(s) similar to 10(3) m/s and the diffusion velocity is u(n) similar to(10-10(2)) m/s estimated in a plasma jet device.