On the Magnetospheric Heating Problem

In the Earth's magnetosphere the specific entropy, increases by approximately two orders of magnitude when transitioning from the magnetosheath into the magnetosphere. However, the origin of this non-adiabatic heating is not well understood. In addition, there exists a dawn-dusk temperature asymmetry in the flanks of the plasma sheet - the cold component ions are hotter by 30-40% at the dawnside plasma sheet compared to the duskside plasma sheet. 

Our recent statistical study of magnetosheath temperatures using 7 years of THEMIS data indicates that ion magnetosheath temperatures downstream of quasi-parallel (dawn-flank for the Parker-Spiral IMF) bow shock are only ~15 percent higher than downstream of the quasi-perpendicular shock. This magnetosheath temperature asymmetry is therefore inadequate to cause the observed level of the plasma sheet temperature asymmetry. 

In this presentation we address the origin of non-adiabatic heating from the magnetosheath into the plasma sheet by utilizing small Cluster spacecraft separations, 9 years of statistical THEMIS data as well as Hall-MHD and hybrid simulations. 

We present evidence of a new physical mechanism capable of cross-scale energy transport at the flank magnetopause with strong contributions to the non-adiabatic heating observed between the magnetosheath and plasma sheet. This same heating mechanism may occur and drive asymmetries also in the magnetospheres of gas giants: Jupiter and Saturn, as well as play role elsewhere in the universe where significant flow shears are present such as in the solar corona, and other astrophysical and laboratory plasmas