This scientific article reports the first experimental detection of reflected Alfvén waves from an Alfvén-speed gradient in a laboratory setting, mimicking conditions found in coronal holes on the Sun. The study, conducted in the Large Plasma Device (LAPD) at the University of California, Los Angeles, focused on the impact of Alfvén-speed inhomogeneity on Alfvén wave reflection. The researchers varied the Alfvén-speed gradient and the wavelength of the incident Alfvén wave to study the resulting reflection. The experimental findings were supported by simulations using the Gkeyll code, showing a strong correlation between the strength of the Alfvén-speed gradient and the amount of wave reflection. The research suggests that wave reflection from smooth Alfvén-speed gradients in coronal holes may contribute significantly to the heating of the solar corona, particularly at lower heights, through the process of wave-driven turbulence.

Basic Plasma Science Facility: https://plasma.physics.ucla.edu

Article being discussed: Sayak Bose, Jason M. TenBarge, Troy Carter, Michael Hahn, Hantao Ji, James Juno, Daniel Wolf Savin, Shreekrishna Tripathi, and Stephen Vincena, “Experimental Study of Alfvén Wave Reflection from an Alfvén-speed Gradient Relevant to the Solar Coronal Holes”, The Astrophysical Journal, 971:72, 12pp, (2024); https://dx.doi.org/10.3847/1538-4357/ad528f

The Gkeyll 2.0 simulation code: https://gkeyll.readthedocs.io/en/latest/

The Basic Plasma Science Facility is a Collaborative Research Facility that is primarily funded by the US Department of Energy Fusion Energy Sciences program, with additional funding from the National Science Foundation.