Adiabatic-radiative shock systems in YSO jets and novae outflows

TL;DR

This paper investigates the simultaneous occurrence of adiabatic and radiative shocks in jets from young stars and novae, using analytical, numerical, and laboratory scaling methods to explore their physical implications and potential for particle acceleration.

Contribution

It provides the first comprehensive analysis of conditions allowing coexistence of adiabatic and radiative shocks in astrophysical jets, supported by simulations and laboratory experiment scaling.

Findings

Coexistence of adiabatic and radiative shocks is feasible in jet termination regions.

Instabilities at contact discontinuities lead to mixing of shocked materials.

Laboratory experiments can replicate these shock conditions for further study.

Abstract

The termination regions of non-relativistic jets in protostars and supersonic outflows in classical novae are nonthermal emitters. Given the high densities in these systems, radiative shocks are expected to form. However, in the presence of high velocities, the formation of adiabatic shocks is also possible. A case of interest is when the two types of shocks occur simultaneously. These dense jets/outflows are excellent candidates for laboratory experiments as demonstrated by MHD scaling. We aim at studying the combination of adiabatic and radiative shocks in these systems. We focus on determining the conditions under which this combination is feasible together with its physical implications. We perform an analytical study of the shocks in both types of sources for a set of parameters. The hydrodynamical evolution of a jet colliding with an ambient medium is studied with 2D numerical simulations confirming our initial theoretical estimates. We show that for a wide set of parameters the combination of an adiabatic and a radiative shock is possible at the working surface of the termination region in jets from young stars and novae outflows. We find that instabilities are developed at the contact discontinuity, mixing the shocked materials. Also, we explore the MHD parameter scaling required for studying protostellar jets and novae outflows using laboratory experiments on laser facilities. The coexistence of an adiabatic and a radiative shock is expected at the termination region of protostellar jets and novae outflows. This scenario is very promising for particle acceleration and gamma-ray emission. The parameters for scaled laboratory experiments are very much in line with plasma conditions achievable in currently operating high-power laser facilities. This opens the door to new means for studying novae outflows never considered before.