New Publication: “Electron Heating Scales in Collisionless Shocks Measured by MMS” by Andreas Johlander at al.

Electron heating at collisionless shocks in space is a combination of adiabatic heating due to large-scale electric and magnetic fields and non-adiabatic scattering by high-frequency fluctuations. The scales at which heating happens hints to what physical processes are taking place. In this letter, we study electron heating scales with data from the Magnetospheric Multiscale (MMS) spacecraft at Earth’s quasi-perpendicular bow shock. We utilize the tight tetrahedron formation and high-resolution plasma measurements of MMS to directly measure the electron temperature gradient. From this, we reconstruct the electron temperature profile inside the shock ramp and find that the electron temperature increase takes place on ion or sub-ion scales. Further, we use Liouville mapping to investigate the electron distributions through the ramp to estimate the deHoffmann-Teller potential and electric field. We find that electron heating is highly non-adiabatic at the high-Mach number shocks studied here.

Electron temperature profiles for the three shock crossing events. The x-axes show the profile along urn:x-wiley:00948276:media:grl65419:grl65419-math-0015 which means that upstream is at higher values regardless of which direction the spacecraft crossed the shock. Units are km on the bottom and di,u on the top. The shortest distance where half the temperature increase takes place is marked in gray.

Full Article:
Johlander, A. (SHARP), Khotyaintsev, Y. V. (SHARP), Dimmock, A. P. (SHARP), Graham, D. B. (SHARP), & Lalti, A. (SHARP) (2023). Electron heating scales in collisionless shocks measured by MMS. Geophysical Research Letters, 50, doi: 10.1029/2022GL100400

License: CC BY 4.0