A comparison of Pi2 pulsations observed by CHAMP in low Earth orbit and on the ground at low latitudes

Abstract

Initial results of a comparative study of Pi2 pulsations observed by the CHAMP satellite in low Earth orbit and at a low‐latitude ground station in South Africa are presented. It has for the first time been possible to extract and clearly resolve Pi2 pulsations from low Earth orbit satellite data due to the unprecedented accuracy and resolution of the CHAMP magnetic field measurements. An important new result is that the correlation between satellite and ground Pi2s is improved by subtraction of a lithospheric magnetic field anomaly model from the satellite data. The analysis indicates that the H‐component of the Pi2 pulsation on the ground is well correlated with the compressional and poloidal components above the ionosphere. Furthermore, in the southern hemisphere the compressional and poloidal components oscillate in phase with H; however, in the northern hemisphere the poloidal component oscillates in anti‐phase with the compressional and H components.