Primary neutral helium in the heliosphere

TL;DR

This paper presents modeling of neutral helium in the heliosphere based on IBEX-Lo measurements, aiming to understand interstellar medium interactions and secondary neutral particle production.

Contribution

It introduces a coupled modeling approach combining global heliosphere simulations with analytic neutral trajectory calculations to estimate neutral helium distribution.

Findings

Identification of primary interstellar helium in the inner heliosphere

Evidence of secondary neutral helium and oxygen creation within the heliosphere

Enhanced understanding of neutral particle dynamics in the heliosphere

Abstract

Two years of neutral measurements by IBEX-Lo have yielded several direct observations of interstellar neutral helium and oxygen during preferred viewing seasons. Besides the interstellar signal, there are indications of the presence of secondary neutral helium and oxygen created in the heliosphere. Detailed modeling of these particle species is necessary to connect the measured fluxes to the pristine local interstellar medium while accounting for loss and production of neutral particles during their path through the heliosphere. In this contribution, global heliosphere models are coupled to analytic calculations of neutral trajectories to obtain detailed estimates of the neutral distribution function of primary interstellar helium atoms in the heliosphere, in particular in the inner heliosphere.