Excitation of the third harmonic mode in meridian planes for Pi2 in the auroral zone

摘要

Polarizations of Pi2 pulsations in the magnetosphere and on the ground in the auroral zone are inconsistent when field line motions in the meridian and transverse planes are both in the fundamental harmonic. To resolve these inconsistencies, we propose a third harmonic mode in the meridian planes. The excitation of the third harmonic is explained by dusk-to-dawn currents at the equatorial plane, which are driven by diamagnetic currents during substorm injections. We propose diamagnetic currents in the equatorial plane and compressional input at the outer boundary as the source of Pi2 pulsations in the magnetosphere.