Authors: Sayak Bose (Princeton University, Princeton Plasma Physics Laboratory), Troy Carter (Oak Ridge National Laboratory), Michael Hahn (Columbia University), Daniel Wolf Savin (Columbia University) and Steve Vincena (University of California Los Angeles)

Alfvén wave phase mixing is one of the leading theoretical mechanisms for coronal hole heating, yet investigations into its effectiveness have remained confined to theory and simulations for over four decades. Here, we report the first laboratory experiments of Alfvén wave phase mixing under conditions scaled to match solar coronal holes. Our results clearly demonstrate that phase mixing drives energy from an initially low perpendicular wave number  to higher values, leading to significantly enhanced wave damping. Conducted on the Large Plasma Device at UCLA, the experiments varied the transverse density gradient, the primary driver of phase mixing from a uniform plasma to both Wentzel–Kramers–Brillouin (WKB) and strong non-WKB regimes. In the WKB regime, the observed wave damping agrees with theoretical predictions. By synthesizing our experimental results with existing solar observations, we analyze the impact of phase-mixing in heating coronal holes.