The Frequency and Global Structure of High-m Poloidal Waves and Their Relationship to ST-5 Observations

The NASA ST-5 satellites detected wave events that appeared to have frequencies in the Pc 2-3 bands (Le et al. 2011). In a later study, it was confirmed that these wave events are, in fact, Doppler shifted high-m poloidal waves, having frequencies in Pc 5 band with no significant dependence on L (Chi et al. 2015). We consider these observations in the context of the kinetic fluid model (Cheng and Johnson 1999) in combination with a quasi-static equilibrium model with anisotropic pressure (Cheng 1992). High-m poloidal waves can be described with asymptotic eigen-solutions to an MHD ballooning equation expanded about 1/m². These eigenmodes are characterized by a spread across a range of L, consistent with observations that the frequency of high-m poloidal waves are independent of L.