Anomalous diffusion and oscillations of the positive column in a magnetic field

Relation between anomalous diffusion and oscillations of the positive column located in the longitudinal magnetic field in the range 0∼2,200 gauss was studied to examine the theory of Kadomtsev and Nedospasov. By investigation of intensity and spectrum of the oscillations in the region of anomalous diffusion, higher harmonics of high frequency oscillation of the order 1 Mc/s were detected. It is concluded that the excitation of high frequency oscillation is the essential cause of anomalous diffusion phenomenon in opposition to the theory of Kadomtsev and Nedospasov. In addition, we investigated the set-in-magnetic-field of helical instability by changing the intensity of low frequency oscillation and found that the set-in-magnetic-field decreases with increasing intensity of pre-helical oscillations. It may relate to the hysteresis characteristics of E_Z-B first proposed by Nakano et al. (author)