Kinetic-Gasdynamic Modeling of the Heliospheric Interface

Abstract

Heliospheric energetic neutral atoms (ENAs) that will be measured by the Interstellar Boundary Explorer (IBEX) originate from the heliosheath. The heliosheath is formed as a result of the interaction of the solar wind (SW) with the circum-heliospheric interstellar medium (CHISM). The expected fluxes of ENAs are strongly dependent on the nature of this interaction. In turn, the interaction of the solar wind with the local interstellar cloud has a complex and multi-component nature. Detailed theoretical modeling of the interaction between the SW and the local interstellar medium is required to understand the physics of the heliosheath and to predict and explain the heliospheric ENAs. This paper summarizes current state-of-art kinetic-gasdynamic models of the SW/CHISM interaction. We shall restrict our discussion to the kinetic-gasdynamic and kinetic-magnetohydrodynamic (MHD) models developed by the Moscow group. This paper summarizes briefly the main results of the first self-consistent, two-component, kinetic-gasdynamic model by Baranov and Malama (J. Geophys. Res. 98:15157-15163, 1993), presents new results obtained from the 3D kinetic-MHD model by Izmodenov et al. (Astron. Astrophys. 437:L35-L38, 2005a), describes the basic formulation and results of the model by Malama et al. (Astron. Astrophys. 445:693-701, 2006) as well as reports current developments in the model. This self-consistent model considers pickup protons as a separate non-equilibrium component. Then we discuss a stochastic acceleration model for pickup protons in the supersonic solar wind and in the heliosheath. We also present the expected heliospheric ENA fluxes obtained in the framework of the models.

Constraining the pickup ion abundance and temperature through the multifluid reconstruction of the Voyager 2 termination shock crossing

“…Most global models of the outer heliosphere treat the ion components of the solar wind as a single MHD fluid [Opher et al, 2006[Opher et al, , 2009Pogorelov et al, 2007;Alouani-Bibi et al, 2011;Ratkiewicz and Grygorczuk, 2008;Izmodenov et al, 2009]. These models do not yield a self-consistent description of the pickup ions; therefore, additional assumptions are needed to link the upstream pickup ion pressure with the downstream pickup ion pressure across the termination shock [Zank et al, 1996[Zank et al, , 2010Fahr and Chalov, 2008].…”

Low Energy Neutral Atoms From the Heliosheath

“…This neutral exchanges charge a second time beyond the heliopause, creating a pickup ion in the nearby interstellar medium. The pickup ion exchanges charge a third time, creating a neutral atom that returns to the inner solar system (Izmodenov et al 2009;Chalov et al 2010;Heerikhuisen et al 2010). Process 3b in Figure 1 is shown for a solar wind ion in the heliosphere.…”

“…Additional discussion of the secondary ENA process and other ENA populations is found in Izmodenov et al (2009) and Chalov et al (2010). For a recent review of processes that may create the IBEX ribbon, see McComas et al (2014).…”

LATITUDINAL AND ENERGY DEPENDENCE OF ENERGETIC NEUTRAL ATOM SPECTRAL INDICES MEASURED BY THEINTERSTELLAR BOUNDARY EXPLORER

“…In addition to these heliospheric sources, a substantial fraction of the <0.5 keV ENAs in the GDF observed by IBEX-Lo could also originate from suprathermal ions and/or PUIs that exist near the heliopause or beyond in the disturbed LISM region just outside the heliopause known as the outer heliosheath (see Izmodenov et al 2009;Chalov et al 2010;Heerikhuisen et al 2010Heerikhuisen et al , 2014Heerikhuisen & Pogorelov 2011;Fuselier et al 2012Fuselier et al , 2014Opher et al 2013;Desai et al 2014;Zirnstein et al 2014).…”