Effects of radiative energy losses on the structure of stellar wind interaction with the interstellar medium
We present two-dimensional axisymmetric gas dynamic simulations of the hypersonic stellar wind interaction with the surrounding interstellar medium moving with supersonic speed in the stellar rest frame. Our model takes into account radiative losses that appear in optically thin plasma. We aim to explore the influence of radiative cooling on the size and global shapes of astrospheres. It is demonstrated in the paper that solution depends on five dimensionless parameters: 𝛾 (the adiabatic index), 𝑀∞ (the Mach number in the undisturbed interstellar medium), 𝜒 (the ratio between terminal speed and interstellar medium speed), as well as 𝛼 and 𝜃 which are related to the energy losses; 𝛼 is responsible for radiative cooling power, 𝜃 is the interstellar medium temperature divided by 104 K. Results of the simulations demonstrate that radiative losses have a significant influence on the flow pattern. The process of radiative cooling leads to an increase of density and pressure which results in compression of the interaction region and changing the position of the astropause. We also explore the growth of Kelvin-Helmholtz instability appearing at tangential discontinuities with increasing cooling power 𝛼.