Laboratory measurement of Alfvén waves propagation through a parallel Alfvén speed gradient*

Alfvén waves are important in many astrophysical systems and various laboratory plasmas. Astrophysical phenomena such as solar coronal heating and the acceleration of charged particles in the magnetosphere involve inhomogeneous plasmas with complex magnetic structures. Investigating Alfven waves traveling through inhomogeneous plasmas is essential for understanding turbulence, damping, and heating. We are studying the behavior of inertial Alfvén waves (electron thermal speed << Alfvén speed) as they propagate through Alfvén speed gradients in the laboratory. We have performed a series of experiments at the Large Plasma Device (LAPD) at the University of California, Los Angeles, to measure the reflection and transmission of Alfvén waves through a gradient parallel to the background magnetic field. The inhomogeneity was created by varying the magnetic field in the direction of the propagation of the Alfvén wave. We have observed the reflection of inertial Alfvén waves as they propagate through these Alfvén speed gradients. We will present the results of these experiments.