Large-scale vortices in the solar photosphere: statistical properties and the reliability of local correlation tracking

Vortices are observed throughout the solar atmosphere, spanning a wide range of spatial scales. Although small-scale vortices have been studied extensively, mesoscale vortices remain less explored, and it is still unclear whether they can be reliably recovered from observations. Mesogranular-scale motions are recovered from the R2D2 simulations by applying Gaussian spatial smoothing to the horizontal velocity field with full width at half maximum (FWHM) values of 2.5–4.0 Mm. To evaluate the accuracy of local correlation tracking (LCT) and its suitability for identifying mesogranular vortices, we apply LCT to synthetic intensity maps at τ = 1 using the same spatial windows and temporal averaging windows of 10–60 minutes. Vortices are identified in both the reference and LCT-derived velocity fields using the Γ method. For all tested parameter combinations, LCT underestimates the number of mesogranular-scale vortices. The best overall recovery is obtained for relatively small spatial smoothing scales (FWHM ≤3.5 Mm) and short averaging windows (≤20 minutes), which provide the most reliable vorticity and lifetime statistics while maintaining strong agreement in vortex radius and area distributions. Our analysis shows that only a modest fraction of LCT-detected vortices correspond to vortices identified in the reference velocity field (3.54%–17.88%), depending on FWHM and temporal averaging. This indicates that vortex-driven dynamics inferred from LCT-detected vortices should be interpreted with caution. Our results suggest that applying the Γ method to LCT-derived velocity fields can recover useful statistical properties of mesoscale vortical structures, especially their temporal trends and characteristic sizes.