Global ULF disturbances during a stormtime substorm on 25 September 1998

摘要: [1] Quasiperiodic perturbations of ionospheric plasma with ∼10 min occurrence periods were observed by incoherent scatter radars (ISR) in high-latitude and midlatitude ionosphere after the onset a stormtime substorm. The latter occurred during period complex dynamical activity had number unusual characteristics. indicate ultralow frequency (ULF) electric field enhancements over Northern Hemisphere. Specifically, strong subauroral fields are associated ring current-related polarization jet (PJ). These correlate magnetic variations regions spanning ∼21 hours local time (MLT). radar ground magnetometer data supported simultaneous observations from DMSP geostationary satellites. As result onset, preexisting PJ shifted equatorward to L ∼ 2.5. Similar periodicities solar wind dynamic pressure interplanetary (IMF) appear be natural sources ULF at high middle latitudes.