Pi2 pulsations in the inner magnetosphere simultaneously observed Jy the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer and Dynamics Explorer 1satellites

摘要

We statistically studied the spatial characteristics of Pi2 pulsations using magnetic fi eld observations in the magnetosphere at the equatorial-orbiting Active Magnetospheric Particle Tracer Explorers (AMPTE)/Charge Composition Explorer (CCE) and the polarorbiting Dynamics Explorer 1 (DE 1) satellites and on the ground at the low-latitude station Kakioka (KAK, L = 1.23). We defined Pi2 pulsations from wavelet analysis of KAK data covering August 1984 to January 1989 and obtained 849 nightside (20:00-04:00 LT) events. For each KAK Pi2 event, we evaluated the coherence between the ground H component and the magnetospheric radial (BLS, , azimuthal (13±A), and compressional (B_∥) components at the frequency of the ground Pi2. High-coherence ground-satellite Pi2 events were found most often in B_∥, with many of them evident at both spacecraft when CCE was located near the equator (magnetic latitude <30°) and inside of the plasmapause estimated from an empirical formula while DE 1 was located at ingh latitude (>30°) and outside of the estimated plasmapause. In these simultaneous CCE and DE 1 events, the B_∥ amplitude was larger at CCE; in addition, the H-B_∥ cross phase was ~0° at CCE but was ~180' at DE 1. We show detailed analysis of one such event as well as two other events that occurred when CCE was outside of the estimated plasmapause and exhibited different coherence and cross-phase properties at this spacecraft. Overall, the two-satellite observations provide additional evidence of plasmaspheric virtual resonance, which was previously suggested from studies using single satellites.