New Publication: “Scattering of Superthermal Ions at Shocks: Dependence on Energy” by Michael Gedalin et al.

Diffusive shock acceleration requires the production of backstreaming superthermal ions (injection) as a first step. Such ions can be generated in the process of scattering of ions in the superthermal tail off the shock front. Knowledge of the scattering of high-energy ions is essential for matching conditions of upstream and downstream distributions at the shock transition. Here we analyze the generation of backstreaming ions as a function of their initial energy in a model stationary shock and in a similar rippled shock. Rippling substantially enhances ion reflection and the generation of backstreaming ions for slightly and moderately superthermal energies, and thus is capable of ensuring ion injection into a further diffusive shock acceleration process. For high-energy ions, there is almost no difference in the fraction of backstreaming ions produced and the ion distributions between the planar stationary shock and the rippled shock.

Left column: the distribution of the forward-moving incident ions fu (v∥, v⊥). Upper middle: the distribution of the ions far downstream of the shock fd (v∥, v⊥) without rippling. Bottom middle: the distribution of the ions far downstream of the shock fd (v∥, v⊥) in the rippled shock. Upper right (empty in this case): the distribution of the backstreaming ions fb (v∥, v⊥) without rippling. Bottom right: the distribution of the backstreaming ions fb (v∥, v⊥) in the rippled shock. The initial ion distribution is isotropic with vp = 0.5.

Full Article:
Gedalin, M. (SHARP), Ganushkina, N. (SHARP), Pogorelov, N. V., Roytershteyn, V. (2023). Scattering of Superthermal Ions at Shocks: Dependence on Energy. The Astrophysical Journal, 957, doi: 10.3847/1538-4357/ad04dd

License: CC BY 4.0