Existence of small-scale Rossby waves points to low convective velocity amplitudes in the Sun.

This article focuses on the detection and characterization of solar equatorial Rossby waves— a class of inertial waves in the Sun’s rotating convective zone—using approximately 13 years of high-resolution observational data from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). By applying helioseismic ring-diagram analysis (RDA) and local correlation tracking (LCT) methods to surface flow maps, the study identifies Rossby modes up to azimuthal order \( m = 34 \), extending beyond previous detection limits. The observed mode frequencies deviate significantly from the classical thin-shell Rossby-Haurwitz dispersion relation at higher \( m \), becoming prograde relative to the solar equatorial rotation rate, and their linewidths increase with \( m \), indicating shorter lifetimes. Numerical modeling using a spectral eigenvalue solver explores the influence of viscous diffusion and superadiabatic temperature gradients on mode frequencies and lifetimes, suggesting that both parameters affect high-\( m \) modes and that large-scale solar convection has a root mean square turbulent velocity constrained to about 1.7–2 m/s. These findings provide tighter constraints on solar interior turbulence and highlight the potential of inertial modes to probe solar fluid dynamics beyond the reach of traditional acoustic helioseismology.