Electromagnetic fluctuations in a magnetically screened high-beta laboratory plasma

Low-frequency electromagnetic turbulence has been observed in large-volume plasma devices in regions receiving magnetically screened plasma. This magnetic screening is created by activating a large solenoid that generates a strong magnetic field (B_EEF) transverse to the background axial magnetic field (B_z ). The variation in the magnetic field strength of controls plasma diffusion and leads to parametric profile modifications in LVPD. The turbulence is characterized by features of an electromagnetic mode with a frequency in the lower hybrid range (f_ci〈f〈f_LH). The source of free energy for the excited turbulence is believed to be the prevalent finite radial pressure gradient in the system. The excited electromagnetic mode has typical scales for the wave number, k_⊥ ∼ 0.13 cm^-1 , and frequency f∼ 6 kHz, propagating with a phase velocity comparable to the ion acoustic velocity, C_s , in the electron diamagnetic drift direction. It is suggested that the low-frequency pressure gradient-driven electromagnetic mode exhibits coupling with the lower hybrid or whistler wave. Further details will be explained in the presentation.