Universal and local time variations deduced from simultaneous Schumann resonance records at three widely separated observatories

Abstract

A technique is applied to experimental Schumann resonance intensity that separates the universal (UT) and local time (LT) variations. Two orthogonal horizontal magnetic field components were recorded simultaneously at the observatories of Moshiri, Japan (44.4°N, 142.2°E), Lehta, Russia (64.4°N, 34°E), and West Greenwich, Rhode Island, United States (41.6°N, 71.6°W). We use the cumulative magnetic field power integrated over the first three Schumann resonance modes. Diurnal variations were averaged over a month for the period from August 1999 to December 2001 at each site. These records were combined to obtain estimates for the UT daily patterns of the global thunderstorm activity. Diurnal variations of particular months repeat year after year, indicating that space‐time distributions of global thunderstorms are annually replicated with minor deviations. Another technique, based on geometric averaging of records, was used to obtain alternative estimates of the global thunderstorm intensity. Results acquired with both techniques showed an outstanding similarity.