Upper Atmosphere Research Satellite observation of a Pi2 pulsation

Abstract

Satellites in low‐altitude orbits provide unique opportunities to study the ionospheric screening effects on ULF waves propagating from the magnetosphere. This paper presents the first report of observation of a Pi2 pulsation from the Upper Atmosphere Research Satellite (UARS) at an altitude of ∼580 km. The Pi2 pulsation occurred on November 18, 1993, when the satellite was over the Pacific near the three ground magnetometer sites, Chichijima (L = 1.14, MLT = 23), Ewa Beach (L = 1.17, MLT = 03), and Guam (L = 1.07, MLT = 23). On the ground the Pi2 was visible in the H (northward) component from 1337 to 1343 UT at all locations with the same period of 43 s but with an amplitude ranging from 2.1 nT (Guam) to 0.6 nT (Ewa Beach). At the satellite the same pulsation was detected in the H component with an amplitude of 1.7 nT. The transverse radial component and the parallel component at the satellite oscillated in phase, consistent with previous Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer observations at L > 2. When the ground signals are linearly interpolated to the geographic longitude and latitude of UARS, the orientation of the major axis of polarization agreed well with that observed by UARS, as is expected for a fast‐mode wave propagating through the ionosphere.