Energy Conversion and Exchange in a Magnetosheath Jet

Magnetosheath jets are regions with an extremely large dynamic pressure compared to that of the background plasma. We present a case study of a magnetosheath jet examining energy conversion processes and its interaction with the surrounding magnetosheath plasma. To understand the energy conversion processes we use data from the Magnetospheric Multiscale mission (MMS) to calculate the scalar product of the total current density J and the electric field (in the electron flow rest frame) E' and the pressure strain interaction term -(Pα·∇)·uα. Large energy conversion between the fields and flow is observed at the leading edge of the jet where a flow reversal and a strong current is observed. The Walén test suggests that magnetic reconnection may also occur in this region. Significant heating of the electrons through the compressive channel is observed. Within the jet itself, the plasma is cooling, indicative of an expansion of the jet as it evolves. The non-Maxwellianity of the ion and electron velocity distribution functions are calculated using three different measures. The non-Maxwellianity shows spikes for the electrons near the reconnection site, while ions exhibit higher non-Maxwellianity at the front of the jet and a smaller value near the peak of the dynamic pressure. Electrons and ions show similar trends with a time delay, suggesting a relationship between the non-Maxwellianity, indicating the different scale sizes present for both species.

Key Points
A case study of a magnetosheath jet is shown
The energy conversion terms are calculated as well as the non-Maxwellianity
At the leading edge a reconnecting current sheet is present while the jet appears to be cooling or expanding