The half subharmonic excitation of ionization waves in positive columns of glow discharges

The 1/2 subharmonic excitation is studied for the ionization wave in a positive column glow discharge. When an oscillation with about twice the frequency of the resonant one is applied by modulating the discharge current, the 1/2 subharmonic is excited if the applied voltage exceeds a certain critical value. However, the excitation phenomenon differs from that of the ion-acoustic wave, since the ionization wave has a backward wave property in contrast to the forward one. Such an excitation mechanism is theoretically explained by the Van der Pol equation. (author)