Kinetic-Fluid Perspective on Modeling the Heliospheric/Interstellar Medium Interface

Abstract

Content of the invited paper for Workshop "From the Outer Heliosphere to the Local Bubble: Comparison of New Observations with Theory" organized by International Space Science Institute (ISSI) is presented. Main results of the kinetic-fluid model of the solar wind interaction with the partially ionized supersonic flow of the local interstellar medium (LISM) by Baranov and Malama (J. Geophys. Res. 98(A9):15, 163, 1993) and its development by Moscow group to take into account effects of solar cycles, cosmic rays, non-equilibrium processes, magnetic field and so on are given. It is shown that multi-fluid models are not correct for problem considered due to Knudsen number Kn = l ch /L ∼ 1, where l ch is the mean free path of H atoms for collisions connected with the resonance charge exchange, L is the characteristic length of the problem. Important problems connected with the physical properties of the heliospheric boundary and with magnetohydrodynamics (MHD) of the solar wind interaction with the LISM are discussed.

NEUTRAL INTERSTELLAR HELIUM PARAMETERS BASED ON IBEX-Lo OBSERVATIONS AND TEST PARTICLE CALCULATIONS

“…The size of the heliosphere is a result of the pressure balance between the outward pressure of the solar wind, and of the inward pressure from the Local Interstellar Cloud material. The components of the inward and outward pressures have been extensively discussed in the literature (see, e.g., Fahr et al (2000); Baranov (2009)) and include ram and thermal pressure of the solar wind thermal core and pickup ions, magnetic field pressure and pressure of the anomalous and Galactic components of cosmic rays. While the main pressure components from the core of the solar wind at the termination shock are known from in situ measurements of the solar wind (Richardson et al 2008;Burlaga et al 2008), the pressure from pickup ions and the components of the inward pressure from the LIC are known only indirectly, mostly from modeling based on the limited observations available.…”

Kinetic-Gasdynamic Modeling of the Heliospheric Interface

“…We shall restrict our discussion to the kinetic-gasdynamic and kineticmagnetohydrodynamic (MHD) models developed by the Moscow group. A summary of the Baranov and Malama (1993), Izmodenov et al (2001a) in all models below in the table Interstellar plasma: protons, electrons Baranov and Malama (1993) + helium ions Interstellar magnetic field Aleksashov et al (2000), Izmodenov et al (2005a), Izmodenov and Alexashov (2006) Galactic Cosmic Rays Anomalous Cosmic Rays Solar wind (protons, electrons) Baranov and Malama (1993) + alpha particles Pickup ions (kinetic description) Malama et al (2006) Solar Cycle Variations of the solar wind Izmodenov et al (2005b), Latitudinal variations of the solar wind Alexashov & Izmodenov, in preparation See also recent reviews by Baranov and Izmodenov (2006), Baranov (2009) and a book edited by Izmodenov and Kallenbach (2006). For comparison of kinetic and multi-fluid models see relevant publications is given in Table 1.…”