Authors: Paria Abouhamzeh (Department of Space Science, The University of Alabama in Huntsville), Bingbing Wang (Center for Space Plasma and Aeronomic Research), Masaru Nakanotani(Center for Space Plasma and Aeronomic Research), Gary P. Zank (Department of Space Science, The University of Alabama in Huntsville, Center for Space Plasma and Aeronomic Research)

The structure of collisionless shock waves could be modified by energetic particles, such as pickup ions (PUIs) in the heliosphere and galactic cosmic rays  (GCRs) in the interstellar medium. This is particularly evident in the heliosphere and the Very Local Interstellar Medium (VLISM), where observations reveal that PUI pressure surpasses the pressure of the magnetic field and thermal gas. Energetic particles contribute a collisionless heat flux and viscosity, playing a crucial role in the dissipative processes at shock waves and modifying the shock structure. In this work, the strong scattering of the PUIs by the low-frequency MHD turbulence is included explicitly in the fluid model, which is seldom discussed in the literature. As an illustrative example, we considered a one-dimensional two-fluid set of equations and showed the calculated shock structure. This approach aims to provide deeper insights into the role of PUIs in modifying the structure of collisionless shocks in the heliosphere and address the importance of wave-particle interactions.