Propagation of Plasma Diffusion Wave According to the Voltage Polarity in the Atmospheric Pressure Plasma Jet Columns

Propagation of optical signals measured along the atmospheric plasma-jet column according to the operational voltage polarity is analyzed with the electrostatic plasma-diffusion wave in terms of the characteristic speeds of plasma fluids, such as the plasma drift u_d, the gas flow u_b, and the plasma diffusion u_n. For the positive voltage, the ion wave propagates with the wave-packet velocity of u_g ~ c_s²/u_n, where c_s is the acoustic velocity along the whole column of plasma jet without any restrictions. The electron wave propagates backward with the group velocity of electron drift with u_g ~ -u_ed toward the high voltage electrode right after passing of the frontline of ion wave-packet. For the negative voltage, the ion wave propagates on the high ionization column with the wave-packet velocity of u_g ~ c_s²/u_n. The electron wave propagates forward while its propagation mode varies from the group velocity of u_g ~ c_s²/u_n on a region of high electric field to the velocity of electron drift with ug ~ +u_ed on a low field region.