Scaling of reconnection electron heating in the low Beta and high Alfvén speed regime of Earth's magnetotail

We survey 25 reconnection outflow events observed by Magnetospheric MultiScale (MMS) in the low Beta and high Alfvén speed regime of the Earth’s magnetotail to investigate the scaling of electron bulk heating produced by reconnection. The range of inflow Alfvén speeds and inflow electron Beta covered by this study is 1000 – 4000 km/s and 0.002 and 0.2 respectively, and the observed electron heating varies from a few hundred eV to ~2 keV. Thus, the study covers inflow Alfvén speeds and electron heating several orders of magnitude higher than previous scaling studies, in a regime which has applications to solar physics. We find that the amount of heating scales with the available magnetic energy per particle, similar to that found for high Beta plasmas where the inflow Alfvén speed and the amount of heating were orders of magnitude lower. In essence, these findings suggest that the scaling law for electron heating by reconnection could be universal.