On the cavity mode nature of low‐latitude Pi 2 pulsations

Abstract

In this paper confirmatory and new observational evidence is presented in an attempt to clarify the source mechanism of low‐latitude Pi 2 pulsations. We commence by extending our recent investigation on the occurrence of dayside Pi 2 pulsations at low and mid latitudes. Using the technique of data adaptive filtering further evidence is presented to confirm that the pulsations occur almost simultaneously in both the nightside and dayside hemispheres at low latitudes. We then demonstrate that the spectra of the dayside and nightside pulsations are similar. The spectra of Pi 2 pulsations are furthermore compared with those of Pc 3 pulsations and shown to be different in a number of respects. We believe that these various observed characteristics are a consequence of the cavity mode nature of low‐latitude Pi 2 pulsations.