Collisional effects on the lower hybrid drift wave inside the reconnecting current sheet of a laboratory plasma

Abstract:

Lower hybrid drift waves have been observed near the electron diffusion region of the Magnetic Reconnection Experiment (MRX), where finite Coulomb collisions exist. To address possible collisional effects on the generation and propagation of the lower hybrid drift wave (LHDW), we have developed a theoretical framework, which is based on a local linear model and electron fluid equations. Unlike the previous model for collisionless plasma [1], we have modified the expression for electron heat flux and added the effects due to heat generation by collisions with known fluid closures [2,3]. In addition, the first-order perpendicular temperature, which was neglected in the previous model, is included. Preliminary results show that collisional effects for typical MRX parameters are negligible, although finite Coulomb collisions decrease the growth rate. With parameters measured in MRX during reconnection with a relatively high guide field that exceeds the reconnecting field component, the quasi electrostatic LHDW propagating almost perpendicular to the equilibrium magnetic field is unstable. This quasi electrostatic LHDW is capable of generating density fluctuations that are correlated with fluctuations in the electric field, potentially leading to anomalous electron heating which could be important during reconnection.

[1] J. Yoo et al. Lower hybrid drift waves during guide field reconnection, submitted.

[2] J. Ji and E. D. Held, phys. plasmas 20, 042114 (2013).

[3] J. Ji and I. Joseph, phys. plasmas 25, 032117 (2018).