Investigations into the Influence of Heavy Ions on EMIC Wave Propagation in the Earth’s Magnetosphere

Abstract:

Geomagnetic pulsations in the Pc1 frequency range (0.2 to 5.0 Hz), which are known as electromagnetic ion cyclotron (EMIC) waves, are often observed at magnetically conjugate locations by spacecraft in the equatorial magnetosphere and ground-based stations. One difficulty in linking the propagation of detected radiation between these regions is the presence of stop bands near the heavy ion cyclotron resonance locations. Recent full wave calculations (Kim and Johnson, Full wave modeling of EMIC waves in the Earth’s magnetosphere, 2015 AGU fall meeting) demonstrate how EMIC waves propagate to higher magnetic latitudes in an electron-proton-He⁺ plasma. However, while the heavy ion concentration can be large during the solar maximum and geomagnetic storms, they adopted a 5% He⁺ plasma. In this study, we explore the roles of heavy ion (He⁺ and O⁺) concentrations on the levels of EMIC wave energy that reach lower altitudes using a two-dimensional, finite element, full wave model. The Poynting flux and polarization of the emissions are used to monitor the propagation and absorption of wave energy, as well as mode coupling between left- and right-hand circularly polarized modes. Due to the increase in heavy ion populations in the magnetosphere, the consequences that geomagnetic storms have on EMIC wave propagation are also discussed.