Magnetohydrodynamic turbulence experiments in a transverse magnetic field

Random fluctuations in a transverse magnetic field caused by a helium plasma produced in an arc discharge were measured with magnetic probes. Ensemble averaged power spectra of these fluctuations followed a power law over the frequency range from about 0.2 to 1 MHz, the exponents varying from −11/3 to −19/3. The time average of the fluctuation intensity parallel to the external magnetic field increased nearly linearly with the imposed field up to about 1000 G. Stronger magnetic fields inhibited these fluctuations and retarded the flow of the plasma. Integral and microscales were in the range of 40 to 100 mm and 20 to 40 mm, respectively. The random fluctuations in the magnetic field may have been due partly to random inhomogeneities in the conductivity of the plasma and only partly to vortical turbulence. Magnetic and conductivity probes indicated the presence of substantial electrical conductivity ahead of the luminous plasma. This conductivity was reduced by increasing magnetic field, interpreted as involving an electron flux.