Some Impacts of Heavy Ions on Near-Earth Magnetospheric Processes

Abstract:

Heavy ions in the magnetosphere are known to have several impacts on magnetospheric processes. First, the hot oxygen ions of the ion plasma sheet and the cool oxygen ions of the cloak both act to reduce the dayside reconnection rate between the solar-wind and the magnetosphere. During geomagnetic storms, when the magnetosphere is oxygen rich, the reduction of the total dayside reconnection rate may be 10’s of per cent, producing a noticeable reduction in the driving of the magnetosphere. The heavy ions of the plasma cloak reduce the Alfven speed in the dayside magnetosphere, which can reduce the threshold for the Kelvin-Helmholtz instability at the magnetopause, resulting in Kelvin-Helmholtz waves that are stronger and closer to the nose of the magnetosphere; this can lead to a stronger viscous interaction between the solar wind and the magnetosphere and can also lead to enhanced transport of solar-wind plasma into the magnetosphere. By reducing the Alfven speed in the dayside magnetosphere, heavy ions also change the nature of ULF waves, which can impact the radial diffusion and drift-resonant acceleration of radiation-belt electrons and ions. Heavy ions (particularly helium) in the dipolar magnetosphere also change the nature of EMIC waves, altering the wave interaction with ring-current ions and radiation-belt electrons; with EMIC and heavy ions there are several open questions.