Energetic pickup proton population downstream of the termination shock as revealed by the IBEX-Hi data

Abstract

The pickup protons originate as a result of the ionization of hydrogen atoms in the supersonic solar wind, forming the suprathermal component of protons in the heliosphere. While picked by the heliospheric magnetic field and convected into the heliosheath, the pickup protons may suffer the stochastic acceleration by the solar wind turbulence in the region from the Sun up to the heliospheric termination shock, where they can also experience the shock-drift acceleration or the reflection from the cross-shock potential. These processes create a high-energy "tail" in the pickup ion energy distribution. The properties of this energetic pickup proton population are still not well-defined, despite they are vital for the models to simulate energetic neutral atom fluxes. We have considered two scenarios for pickup proton velocity distribution downstream of the heliospheric termination shock (filled shell with energetic power-law "tail" and bi-Maxwellian). Based on the numerical kinetic model and observations of the energetic neutral atom fluxes from the inner heliosheath by the IBEX-Hi instrument, we have characterized the pickup proton distribution and provided estimations on the properties of the energetic pickup proton population downstream of the termination shock.

18 pages, 15 figures

References in corpus (4)

• Interstellar Pickup Ion Observations to 38 AU
• Magnitude and direction of the local interstellar magnetic field inferred from Voyager 1 and 2 interstellar data and global heliospheric model
• Heliospheric Energetic Neutral Atoms: Non-stationary Modeling and Comparison with IBEX-Hi data
• The Confinement of the Heliosheath Plasma by the Solar Magnetic Field as Revealed by Energetic Neutral Atom Simulations

Cited by in corpus (6)

• Thermodynamics of the inner heliosheath
• 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?
• 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