Physics Colloquium-Growth, Propagation, and Effects of Electromagnetic Ion Cyclotron (EMIC) Waves

Richard E. Denton

Dartmouth College, Department of Physics and Astronomy

We use two dimensional hybrid code simulations (full dynamics particle ions, but inertialess fluid electrons) in dipole geometry in order to investigate the growth, propagation, and effects of magnetospheric electromagnetic ion cyclotron (EMIC) waves. The plane of the simulation includes variation in the L shell direction and along magnetic field lines. The waves are driven by pressure anisotropy. They initially grow close to the magnetic equator, but the wave energy then propagates along magnetic field lines toward the ionospheric boundary. As the waves propagate, the wave vector turns away from the magnetic field direction and the polarization becomes more linear. Lower frequency waves are more likely to occur in regions of high particle density (like the plasmasphere). High heavy ion content, especially that of O+, can increase the frequency of the waves and can quench their growth. Radiation belt electrons are scattered in the wave fields, leading to their loss through precipitation to the ionosphere. Most theories predict that only relativistic electrons with energy above the so called "resonant energy" can be efficiently scattered, but we find that there is significant non-resonant scattering at lower energies.