Revision 1

Accepted · first revision · record

Title: Ion-to-electron heating ratio in collisionless turbulence
Plain: Turbulence in a collision-free plasma heats ions and electrons by different amounts. The ratio sets what telescopes see from hot astrophysical gas, and it is not yet pinned down.
Precise: For Alfvenic turbulence cascading to kinetic scales, determine the ion-to-electron heating ratio $Q_{i}/Q_{e}$ as a function of ion $\beta_{i}$, $T_{i}/T_{e}$ and the ratio of compressive to Alfvenic energy injection. An answer is a validated fit $Q_{i}/Q_{e}(\beta_{i}, T_{i}/T_{e})$ consistent with Parker Solar Probe and Solar Orbiter radial temperature profiles.
Settled by: Kinetic simulations in agreement with heating rates inferred from spacecraft temperature profiles across the measured $\beta$ range.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: partially-resolved
Status note: Hybrid gyrokinetic simulations (Kawazura and collaborators, 2019-2020) gave a parametric fit with $Q_{\mathrm{i}}/Q_{\mathrm{e}}$ rising steeply with $\beta_{\mathrm{i}}$; observational confirmation is incomplete.
Posed since: (empty)