Connecting Kinetic and MHD Scales in Flows of Partially Ionized Plasma with Shocks

ORAL

Abstract

Flows of partially ionized plasma are frequently characterized by the presence of both thermal and nonthermal populations of ions. Such flows cannot be modeled using traditional MHD equations and require more advanced approaches to treat them. If a non-thermal component of ions is formed due to charge exchange and collisions between the thermal ions and neutral atoms, it experiences the action of magnetic field, its distribution function is isotropized, and it soon acquires the velocity of the ambient plasma without being thermodynamically equilibrated. This situation, occurs in the outer heliosphere -- the part of interstellar space beyond the solar system whose properties are determined by the solar wind interaction with the local interstellar medium. To describe such flows we have developed a numerical model that describes the flow of plasma with MHD equations, whereas the transport of neutral atoms is modeled kinetically, by solving the corresponding Boltzmann equations. The presence of non-termal (pickup) ions (PUIs) and turbulence they generate requires their kinetic treatment at collisionless shocks. We incorporate such kinetic process intothe global MHD model of the heliosphere by imposing specifcally designed boundariy conditions at the heliospheric termination shock. We describe the model details and comapre simulation results with the IBEX, New Horizons, and Voyager data.

*This work is supported by NSF-BSF grants ts 2010450, 2010144 and 2019744, NASA grants 80NSSC24K0267 and 80NSSC22K0524. 744. It was also partially funded by the IBEX mission as part of NASA's Explorer Program (80NSSC18K0237) and IMAP mission as a part of NASA's Solar Terrestrial Probes (STP) Program (80GSFC19C0). We acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing HPC resources on Frontera supported by NSF award CISE-OAC-2031611 and NASA High-End Computing Program award SMD-17-1537.

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Publication: 1. Bera, R. K., Fraternale, F., Pogorelov, N. V., Roytershteyn, V., Gedalin, M., McComas, D. J., Zank, G. P. (2023), The role of pickup ions in the interaction of the solar wind with the local interstellar medium. I. Importance of kinetic processes at the heliospheric termination shock, Astrophys. J., 954, 147
2. . Bera, R. K., Fraternale, F., Pogorelov, N. V., Roytershteyn, V., Gedalin, M., McComas, D. J., Zank, G. P. (2024), The role of pickup ions in the interaction of the solar wind with the local interstellar medium. II. The effects of solar cycle, Astrophys. J., to be submitted
3. Fraternale, F., Pogorelov, N. V., Heerikhuisen, J. (2021), Transport of Interstellar Neutral Helium throughout the Heliosphere, Astrophys. J. Lett., 921, L24
4. Fraternale, F., Pogorelov, N. V., Bera, R. K. (2023), The Role of Electrons and Helium Atoms in Global Modeling of the Heliosphere, Astrophys. J., 946, 97
6. Gedalin, M., Golan, M., Pogorelov, N. V., Roytershteyn, V. (2022), Change of Rankine–Hugoniot relations during post-shock relaxation of anisotropic distributions, Astrophys. J., 940, 21
7. Gedalin, M., Roytershteyn, V., Pogorelov, N. V. (2023), Shock Heating of Incident Thermal and Superthermal Populations of Different Ion Species, Astrophys. J., 945, 50
8. Pogorelov, N.V., Fraternale, F., Zhang, M. (2024), The global structure of the heliosphere, Nature Astronomy, to be submitted
9. Zhang, M., Pogorelov, N. V., Zhang, Y., Hu, H. B., Schlickeiser, R. (2020), The Original Anisotropy of TeV Cosmic Rays in the Local Interstellar Medium , Astrophys. J., 889, 97

Presenters

  • Nikolai V Pogorelov

    • University of Alabama, Huntersville

Authors

  • Nikolai V Pogorelov

    • University of Alabama, Huntersville

  • Ratan Kumar Bera

    • The University of Alabama in Huntsville

  • Federico Fraternale

    • The University of Alabama in Huntsville

  • Michael Gedalin

    • Ben-Gurion University of the Negev, Beer-Sheva

  • Vadim S Roytershteyn

    • Space Science Institute