Solar vortex detection with velocity field normalization: Eliminating false positives

Small-scale vortices in the solar photosphere play a central role in transporting mass, energy, and momentum into the upper solar atmosphere, yet reliably detecting these structures remains rather challenging. We address this problem by introducing a simple preprocessing step that normalizes the velocity field by its magnitude. Our method preserves flow streamlines while suppressing shear-induced artifacts that lead to spurious detections in nonuniform, high-rotation environments. For validation, we apply this approach to high-resolution Bifrost simulations and evaluate vortex detection using four commonly employed methods: instantaneous vorticity deviation, the λ2 criterion, the Q criterion, and the Γ method. We assess which structures exhibit physically consistent rotation by using the d criterion to automatically detect rotational plasma-flow features, which we use as an approximate ground truth. We find that, in the unnormalized field, a substantial fraction of detections made by the first three methods are false positive detections. Normalization removes most of these. The Γ method detects true vortices but misses a large number of vortical flows. The normalization step yields better-defined and more realistic vortex boundaries. As the Γ method underpins most observational analyses, current studies likely capture only a subset of vortical flows. By comparison, the other three methods detect 4 to 5 times more vortices after normalization, suggesting that the true photospheric vortex coverage may be underestimated by a similar factor. Overall, this physically motivated preprocessing step enhances the accuracy and physical realism of vortex detection and offers a practical enhancement for analyzing vortical flows in turbulent flows.