Origin of magnetosheath jets and energy-source quantification

Determine and quantify the energy sources at kinetic and fluid scales that drive the formation of magnetosheath jets downstream of collisionless shocks, establishing the relative contributions of kinetic-scale structures and macroscopic fluid processes to the observed enhancements in downstream kinetic energy density.

Background

Magnetosheath jets are fast plasma flows observed downstream of Earth's bow shock and other planetary environments, exhibiting kinetic energy densities comparable to or exceeding upstream values. Multiple mechanisms have been proposed (e.g., bow shock ripples, upstream coherent structures like SLAMS, and kinetic processes linked to shock reformation), but observational constraints and the prevalence of kinetic-scale dynamics complicate definitive identification of their origins.

The paper emphasizes that all suggested mechanisms depend on kinetic-scale structures or instabilities, yet the energetic contribution of these kinetic processes to jet formation has not been analytically determined. The authors use a CGL fluid formalism with pressure anisotropy to isolate kinetic contributions and provide initial observational evidence, but they note that fully determining and quantifying the energy sources at kinetic and fluid scales remains outstanding.