Solar Vortices as Conduits for Magnetoacoustic Waves: Multi-Layer Coupling and Their Role in Atmospheric Heating
Vortices are widespread throughout the solar atmosphere and commonly interpreted as channels for Alfvén wave energy transport. However, this interpretation has mostly been inferred from the apparent alignment of rotating plasma structures with the magnetic field, rather than direct evidence of the nature of the waves involved. We present observational and numerical evidence that solar vortices act as coherent waveguides dominated by magnetoacoustic waves in the lower atmosphere, combining high-resolution SST observations and Bifrost simulation data. Using Normalised Mutual Information and Jensen-Shannon Divergence as coupling diagnostics, we provide the first observational identification of a solar vortex footpoint through information-theoretic metrics, locating it in the photospheric region of highest shared information with the chromospheric swirl. Spectral Proper Orthogonal Decomposition separates dominant dynamical patterns, allowing us to identify sausage, kink, and helical wave modes propagating along vortex structures. In the Bifrost simulation, we find no evidence for torsional Alfvén waves supported by vortices below 1 Mm. Instead, the waves supported by vortices are magnetoacoustic, and their energy transport is predominantly compressive in the lower atmosphere, with the magnetic component becoming dominant only at greater heights. Even the compressive wave component alone reaches nanoflare-level magnitudes ($\sim10^{25}$~erg), indicating that vortex-associated compressive perturbations may provide an energetically relevant contribution in regimes where magnetic-energy transport dominates. The recovery of sausage and helical modes in temperature perturbations shows that these modes carry a thermal signature, further supporting their relevance for chromospheric energy transport and localised heating.