Measurement of turbulent fields in a plasma prepared with the aid of magnetic sound

With the aid of a magnetic and an electric probe, turbulent fields (noise) in a magnetized plasma prepared according to the method of magneto-acoustic ionization have been measured. Presence of magnetic noise with a frequency maximum in the region of 12 MHz (ω_i<ω≤ω_e) and low-frequency electric noise with a broad frequency spectrum increasing toward low frequencies and followed down to 80 kHz has been established. The magnetic noise can, by the nature of the frequency spectrum, be identified as free magneto-acoustic vibrations of a plasma column that are excited by non-linear interaction between the plasma and the power wave of the ionizing generator.

The electric noise has both an azimuthal component characteristic of drift waves and an axial component with a phase velocity like ionic sound. Drift-wave excitation is associated with universal inhomogeneous-plasma instability, and ionic-sound excitation can be explained by both non-linear interactions of drift waves and non-stationary phenomena in the ionization process itself.