THEMIS observations of compressional poloidal pulsations in the dawnside magnetosphere: A case study

Abstract

We present results from a case study of compressional poloidal pulsations with periods ranging from 5 to 12 min in the dawn magnetosphere from 1630 to 2000 UT on 27 February 2011. However, we employ THEMIS (Time History of Events and Macroscale Interactions during Substorms) magnetic field, plasma, and energetic particle observations to determine azimuthal wavelengths (7000-27,000 km) and velocities (9-28 km/s) consistent with previous work. We then apply a new method invoking the north to south motion of the THEMIS spacecraft and the fact that the equatorial node exhibited north-south oscillations to derive the meridional structure of the wave in great detail. We determined that the amplitude of the meridional motion of the equatorial node was ∼0.8 R E, and that the meridional wave length exceeded 3 RE. Key Points We studied wave characteristics of poloidal compressional pulsations New method to derive the meridional structure of the wave The amplitude of the meridional motion of the equatorial node was ∼0.8 RE ©2013. American Geophysical Union. All Rights Reserved.