How whistler-mode waves and thermal plasma density control the global distribution of diffuse auroral precipitation and the dynamical evolution of radiation belt electrons

How whistler-mode waves and thermal plasma density control the global distribution of diffuse auroral precipitation and the dynamical evolution of radiation belt electrons

Yosemite National Park

Whistler mode chorus emissions are excited as plasma sheet electrons are injected into the inner magnetosphere during geomagnetically active conditions. Recent theoretical analysis has demonstrated that the chorus emissions are primarily responsible for the precipitation of 100 eV - 30 keV electrons into the upper atmosphere and the global distribution of the diffuse and pulsating aurora. Chorus emissions can also cause local stochastic acceleration of the injected electron population to relativistic energies leading to peaks in relativistic electron phase space density in the heart of the radiation belts during magnetic storms. Such local acceleration is most effective when the solar wind dynamic pressure is low and when the thermal plasma density outside the plasmapause is reduced due to rapid magnetospheric convection. Following such acceleration the outward expansion of the plasmapause leaves the injected ultra-relativistic electron population electron in a relatively stable region where they can persist for months subject only to slow decay due to scattering by another whistler-mode emission called plasmaspheric hiss. Since natural whistler-mode emissions play such a fundamental role in controlling energetic electron dynamics in the Earth's magnetosphere, it is likely that similar processes could occur in other magnetized astrophysical objects, such as Jupiter and Saturn.