Typhoon-induced magnetic disturbance: Cases in the western Pacific

Three typhoons occurred on the western Pacific in September 2008 and were enhanced beyond category 3 when they approached Taiwan. Geomagnetic total intensity field recorded at 2 local monitor stations in Taiwan and 1 remote station in Japan are utilized to examine magnetic disturbances induced by these typhoons. Analytical results show that changes in the amplitudes in the frequency domain at the monitor and remote stations are consistent even though magnetic storms intensely affect magnetic fields. However, obvious discrepancy can be repeatedly found from the amplitude at the frequency band between 0.0025 and 0.007 Hz, when the typhoons with category > 3 were the closest to the monitor stations. The frequency band is different with those of induction fields from either oceanic stormy waves or swells, and is consistent with that of magnetic pulsations triggered by acoustic waves from upward air motion during typhoons.