Electron Energization by Dispersive Alfvén Waves in the Cusp

Abstract The propagation of kinetic Alfvén waves (assumed sourced from intermittent dayside reconnection) is investigated with a gyrofluid‐kinetic electron model compared with Cluster observations. These observations reveal electron distributions that are preferentially field‐aligned or field‐opposed, with signatures that are unidirectional or counterstreaming and skews that vary with the current sense. The simulations reproduce, with good fidelity, the observed local characteristics when the conditions match the observed local plasma conditions. The wave energy conversion is predominantly positive at mid‐altitudes, indicating a transfer of wave to electron energy. This conversion rate increases significantly at low‐altitudes (in the inertial Alfvén wave regime) and is accompanied by the formation of highly field‐aligned electron beams peaking at several hundred eV in energy, with a directionality that is opposite to the current sense. This low‐altitude energization results in the dissipation of the majority of the wave Poynting flux and would lead to substantial soft electron precipitation.