Electromagnetic Ion Cyclotron Wavefields in a Realistic Dipole Field

The latitudinal distribution and properties of electromagnetic ion cyclotron (EMIC) waves determine the total effect of those waves on relativistic electrons. Here we describe the latitudinal variation of EMIC waves simulated self-consistently in a dipole magnetic field for a plasmasphere or plume-like plasma at geostationary orbit with cold H+, He+, and O+ and hot protons with temperature anisotropy. The waves grow as they propagate away from the magnetic equator to higher latitude, while the wave vector turns outward radially and the polarization becomes linear. We calculate the detailed wave spectrum in four latitudinal ranges varying from magnetic latitude (MLAT) close to 0 degrees (magnetic equator) up to 21 degrees. The strongest waves are propagating away from the magnetic equator, but some wave power propagating toward the magnetic equator is observed due to local generation (especially close to the magnetic equator) or reflection. The He band waves, which are generated relatively high up on their dispersion surface, are able to propagate all the way to MLAT = 21 degrees, but the H band waves experience frequency filtering, with no equatorial waves propagating to MLAT = 21 degrees and only the higher-frequency waves propagating to MLAT = 14 degrees. The result is that the wave power averaged k(vertical bar), which determines the relativistic electron minimum resonance energy, scales like the inverse of the local magnetic field for the He mode, whereas it is almost constant for the H mode. While the perpendicular wave vector turns outward, it broadens. These wavefields should be useful for simulations of radiation belt particle dynamics. Plain Language Summary Electromagnetic ion cyclotron waves are thought to be important because of their effect on high-energy particles in the region surrounding the Earth called the inner magnetosphere. This paper describes the detailed properties of these waves, including how they evolve as they propagate along the Earth's magnetic field lines. The wavefields are saved in supporting information data sets, which can be accessed online for future studies.