Delayed Correlations Between Geomagnetic Activity and Human EEG Alpha and Theta Oscillations: Evidence from Archival and Experimental Data

Neural oscillations in the alpha and theta bands have been linked to environmental factors, including geomagnetic disturbances, yet the temporal dynamics of these interactions remain poorly understood. This study examined the relationship between geomagnetic activity, quantified by the Kp index, and brain activity in low alpha (7–10 Hz) and theta (4–7 Hz) bands using two complementary approaches. In Experiment 1, archival EEG data from 238 subjects collected over four years were analyzed for correlations between daily Kp values and band power across a ±90-day window. Significant positive correlations (p < 0.01) emerged in both bands, with a spatially coherent peak in caudal regions occurring 19 days prior to EEG measurement. In Experiment 2, an independent sample of 22 participants was exposed to a simulated geomagnetic storm, and EEG was recorded at baseline and 19 days post-exposure. Paired-samples t-tests revealed significant within-subject reductions in theta, low alpha, and high alpha power over frontal and parietal regions, consistent with a delayed neural response. Together, these findings provide converging correlational and experimental evidence for a lagged influence of geomagnetic activity on human brain oscillations. The 19-day delay observed in both datasets suggests that geomagnetic disturbances may exert residual effects on neural dynamics well beyond immediate exposure, warranting further investigation into underlying mechanisms and potential behavioral relevance.