Abstract
Abstract
We report low-frequency electromagnetic turbulence in large-volume plasma devices in a region that receives magnetically screened plasma. The magnetic screen is produced by the activation of a large solenoid that generates a strong magnetic field (
B
EEF
) transverse to the background axial magnetic field (
B
z
). The magnetic field strength variation in
B
EEF
controls the plasma diffusion and is responsible for parametric profile modifications in large volume plasma devices. The turbulence is characterized by the observed features of an electromagnetic mode having frequency ordering in the lower hybrid range (f
ci < f < f
LH). The free energy source for the excited turbulence is believed to be the prevalent finite radial pressure gradient in the system. The excited electromagnetic mode shows typical scales for the wave number,
k
⊥
∼ 0.13 cm−1 and frequency f ∼ 6 kHz and propagates with phase velocity comparable to ion acoustic velocity, C
s in electron diamagnetic drift direction. It is believed that the low-frequency pressure gradient-driven electromagnetic mode exhibits coupling with the lower hybrid or whistler wave.