Evaluation of a GNSS-derived RTK-RISK indicator against global space-weather indices during the May 2024 geomagnetic storm

Abstract Severe space-weather events can produce rapid temporal and spatial ionospheric disturbances that degrade high-precision Global Navigation Satellite System (GNSS) positioning. This study evaluates a regional GNSS-derived RTK-RISK indicator against independent global space-weather and geomagnetic indices during the extreme geomagnetic storm of 11 May 2024. RTK-RISK combines regional Rate of Total Electron Content Index (ROTI) variability and spatial vertical total electron content (VTEC) gradients derived from a Latvian continuously operating reference station network. The indicator and its individual components were compared with the geomagnetic Dst and Kp indices, the interplanetary magnetic field Bz component, its southward component Bs, solar-wind speed, and the coupling proxy VswBs. Spearman rank correlation was used as the principal measure of association. The strongest statistically significant simultaneous relationship with RTK-RISK was observed for Dst (ρ = −0.63). Kp showed a positive association of ρ = 0.65, although this relationship did not reach statistical significance (p = 0.078, N = 8) at its native 3-h resolution. Significant simultaneous associations were also observed for Bs (ρ = 0.41), Bz (ρ = −0.40), and VswBs (ρ = 0.35). The signs of these relationships were physically consistent with enhanced geomagnetic activity and southward interplanetary magnetic field conditions. The results indicate that the independently derived regional RTK-RISK indicator responds coherently to global space-weather conditions and provides a locally resolved measure of ionospheric disturbance relevant to RTK positioning reliability.