Global Pc5 Pulsations From the Polar Cap to the Equator: Wave Characteristics, Phase Variations, Disturbance Current System, and Signal Transmission

Abstract

AbstractWe present observations of global Pc5 pulsations by ∼180 ground magnetometers during the recovery phase of an intense geomagnetic storm. Measurements of magnetic fields along four latitudinal magnetometer chains and one longitudinal magnetometer chain are used to determine the wave characteristics of Pc5 pulsations. Many new features of Pc5 pulsations are identified from a single event for the first time. The Pc5 pulsations occur simultaneously at all latitudes and longitudes/local times, and the period of the Pc5 pulsations is about 10 min and does not depend on latitude and longitude. The latitudinal distributions of the northward (H) component and magnetic pressure of Pc5 perturbations are derived. The phase of the H component reverses across 50–70° magnetic latitude (MLat) but is nearly the same at middle and low latitudes. The phase of the H component at low latitudes does not vary much with longitude/local time. The phase of the D component magnetic field reverses near the equator in the latitudinal direction and also reverses around dawn, noon, dusk, and midnights in the longitudinal direction. The distribution and evolution of global ionospheric equivalent disturbance currents during Pc5 pulsations are derived. A coupled magnetospheric‐ionospheric current system is proposed to explain the observed characteristics of global Pc5 pulsations. It is suggested that the variations of the phase of Pc5 pulsations with latitude and local time are determined by the global distribution of the coupled magnetospheric‐ionospheric current system but not caused by propagation delay of the signals.