Abstract: "Space weather—fluctuations in solar wind and geomagnetic activity—affects multiple biological systems, but whether these effects extend to human behavior at population scales remains controversial. We examined relationships between solar activity and violent deaths in Uruguay and Australia, two countries at similar southern latitudes but fundamentally different electromagnetic environments. Uruguay sits within the South Atlantic Magnetic Anomaly (SAMA), where Earth's magnetic field weakens to 60% of normal strength; Australia experiences normal field conditions. Analyzing 60 years of mortality data (1964-2023), we found systematic correlation reversal: in Australia, increased solar wind pressure and proton density correlated with increased violence (r = +0.52 to +0.85, p < 0.001), while in Uruguay the same variables correlated with decreased violence (r = -0.40 to -0.60, p < 0.001). This geographic reversal—occurring precisely where Earth's magnetic field geometry changes and holding consistently across suicide, homicide, and combined violence—provides strong evidence that geomagnetic conditions mediate space weather influences on human behavior. Preliminary data from Rio Grande do Sul, Brazil, located adjacent to Uruguay within SAMA, show temporal patterns consistent with our findings. Results suggest electromagnetic environment may be an overlooked factor in violence and mental health epidemiology."