# Interstellar Neutral Gas Species And Their Pickup Ions Inside The Heliospheric Termination Shock. The Large-scale Structures

## TL;DR

This study models the distribution and abundance ratios of interstellar neutral gas and pickup ions inside the heliosphere, highlighting their spatial variations and optimal detection regions during different solar activity phases.

## Contribution

It provides a comprehensive analysis of ISN gas and PUI distributions for multiple species across the entire heliosphere, considering solar cycle effects and identifying detection hotspots.

## Key findings

- He$^+$ and Ne$^+$ PUIs are best detected in the downwind hemisphere within 1 au.
- H$^+$ and O$^+$ PUIs are more detectable from Jupiter to Pluto orbits.
- The study maps the ISN gas density cavities and abundance ratio variations across the heliosphere.

## Abstract

We study the distribution of the interstellar neutral (ISN) gas density and the pick-up ion (PUI) density of hydrogen, helium, neon, and oxygen in the heliosphere for heliocentric distances from inside 1 au up to the solar wind termination shock (TS), both in and out of the ecliptic plane. We discuss similarities and differences in the large-scale structures of the ISN gas and PUIs formed in the heliosphere between various species. We discuss the distribution of ISN gas and PUI densities for two extreme phases of the solar activity cycle, it is the solar minimum and the solar maximum. We identify the location of the ISN gas density cavity of various species. We study the relative abundance ratios of Ne/O, H/He, Ne/He, and O/He for ISN gas and PUIs densities and their variation with location in the heliosphere. We also discuss the modulation of relative abundance ratios of ISN gas and PUIs along the TS. We conclude that the preferable locations for detection of He$^+$ and Ne$^+$ PUIs are in the downwind hemisphere within 1~au, whereas for H$^+$ and O$^+$ PUIs the preferable locations for detection are for distances from Jupiter to Pluto orbits.