# An Improved Parametrized Representation of the Secondary He Neutral Flow in its Source Region

## TL;DR

This paper introduces a new parametrized model for the secondary neutral helium flow in the heliosphere's outer region, improving upon previous laminar flow assumptions and enabling remote measurement of interstellar medium divergence.

## Contribution

It proposes a simple divergent flow parametrization for secondary He particles, enhancing modeling accuracy of the outer heliosheath.

## Key findings

- The new model better fits IBEX data on neutral He flow.
- Secondary He flow can be used to measure ISM flow divergence.
- The approach offers a remote sensing method for heliospheric boundary studies.

## Abstract

Analysis of data from the Interstellar Boundary EXplorer (IBEX) has revealed the presence of a flow of neutral helium through the inner solar system that most likely emanates from the outer heliosheath, where a distinct population of neutral He is produced by charge exchange processes. This secondary He flow has been modeled using codes designed to study interstellar flows through the heliosphere, but a laminar flow is not a good approximation for the outer heliosheath. I present a simple parametrization for a more appropriate divergent flow, and demonstrate how the secondary He particles might provide a means to remotely measure the divergence of the ISM flow around the heliopause.