Heliospheric Energetic Neutral Atoms: Non-stationary Modeling and Comparison with IBEX-Hi data

Abstract

The Interstellar Boundary Explorer (IBEX) has been measuring fluxes of the Energetic Neutral Atoms (ENAs) using the IBEX-Hi (0.3 -- 6 keV) instrument since 2008. We have developed a numerical time-depended code to calculate globally distributed flux (GDF) of hydrogen ENAs employing both 1) 3D kinetic-MHD model of the global heliosphere and 2) reconstruction of atom trajectories from 1 au, where they are observed by IBEX, to the point of their origin in the inner heliosheath (IHS). The key factor in the simulation is a detailed kinetic consideration of the pickup ions (PUIs), the supra-thermal component of protons in the heliosphere, which is "parental" to the ENAs and originates in the region of the supersonic solar wind being picked by the heliospheric magnetic field. As a result of our study, we have concluded that (1) the developed model is able to reproduce the geometry of the multi-lobe structure seen in the IBEX-Hi GDF maps, (2) the GDF is extremely sensitive to the form of the velocity distribution function of PUIs in the IHS, and the accounting for the existence of an additional energetic population of PUIs is essential to explain the data, (3) despite a relatively good agreement, there are some quantitative differences between the model calculations and IBEX-Hi data. Possible reasons for these differences are discussed.

15 pages, 10 figures; accepted for publication in MNRAS

References in corpus (3)

• The effects of a kappa-distribution in the heliosheath on the global heliosphere and ENA flux at 1 AU
• Magnitude and direction of the local interstellar magnetic field inferred from Voyager 1 and 2 interstellar data and global heliospheric model
• The Confinement of the Heliosheath Plasma by the Solar Magnetic Field as Revealed by Energetic Neutral Atom Simulations

Cited by in corpus (9)

• Thermodynamics of the inner heliosheath
• Signature of a heliotail organized by the solar magnetic field and the role of non-ideal processes in modeled IBEX ENA maps: a comparison of the BU and Moscow MHD models
• Energetic pickup proton population downstream of the termination shock as revealed by the IBEX-Hi data
• Backscattered solar Lyman-alpha emission as a tool for the heliospheric boundary exploration
• The strong effect of electron thermal conduction on the global structure of the heliosphere
• Adiabatic energy change in the inner heliosheath: How does it affect the distribution of pickup protons and energetic neutral atom fluxes?
• On the anisotropic velocity distribution of newborn pickup ions in the heliosheath
• Impact of Stochastic Acceleration on the Pickup Proton Distribution and ENA Fluxes in the Heliosphere
• Understanding the IBEX ribbon using the kinetic model of pickup proton transport in a scatter-free limit