Modeling the Solar Wind at the Ulysses, Voyager, and New Horizons Spacecraft

TL;DR

This paper presents a three-dimensional, time-dependent model of the solar wind from 1 to 80 AU, integrating observational data to simulate and analyze the solar wind's behavior in the outer heliosphere and along spacecraft trajectories.

Contribution

It introduces a novel two-fluid model that captures the solar wind's dynamics across the entire outer heliosphere using observational boundary conditions.

Findings

Model agrees with Ulysses and Voyager data

Successfully reproduces solar wind parameters along New Horizons trajectory

Provides insights into solar wind behavior near Pluto

Abstract

The outer heliosphere is a dynamic region shaped largely by the interaction between the solar wind and the interstellar medium. While interplanetary magnetic field and plasma observations by the Voyager spacecraft have significantly improved our understanding of this vast region, modeling the outer heliosphere still remains a challenge. We simulate the three-dimensional, time-dependent solar wind flow from 1 to 80 astronomical units (AU), where the solar wind is assumed to be supersonic, using a two-fluid model in which protons and interstellar neutral hydrogen atoms are treated as separate fluids. We use 1-day averages of the solar wind parameters from the OMNI data set as inner boundary conditions to reproduce time-dependent effects in a simplified manner which involves interpolation in both space and time. Our model generally agrees with Ulysses data in the inner heliosphere and Voyager data in the outer heliosphere. Ultimately, we present the model solar wind parameters extracted along the trajectory of New Horizons spacecraft. We compare our results with in situ plasma data taken between 11 and 33 AU and at the closest approach to Pluto on July 14, 2015.