A multistation study of low latitude Pc3 geomagnetic pulsations

Abstract

An array of four low latitude induction coil magnetometer stations has been used to study the spatial and temporal characteristics of Pc3 pulsations over a longitudinal range of 17° at L = 1.8−2.7 in Southeast Australia. Pc3 data over a period of about 6 months have been investigated. Interstation phase variations and polarization characteristics have been investigated in detail for 10 selected individual days common to all four stations. The East-West station chain shows generally highest coherency between X (North-South) components with relatively small interstation phase differences corresponding to low azimuthal wave numbers (| m x , y | ≲ 10). Wave spectra are generally the same at the azimuthai stations ( L = 1.8) but are often different at the higher latitude station ( L = 2.7) while wave polarization ellipticities and major axis azimuth directions at all four stations are generally similar. Diurnal variations in interstation phase indicate that Pc3 waves propagate away from local noon towards the night time with left-hand polarization and North-East major axis azimuth directions in the morning and right-hand polarization and North-West azimuth directions in the afternoon. Apparent meridional propagation is always away from the equator from North to South with | m x , y | < 12. These properties are all consistent with Pc3 wave generation by a field line resonance situated South of the network at L > 3. The resonance may be associated with the plasmapause region or field line resonances resulting from coupling with a global compressional wave mode of low wave number which is capable of propagating energy from the subsolar upstream or magnetosheath regions into the magnetosphere and down to lower latitudes near the noon meridian.