Year: 2025
Type: article
Abstract: We examine the transition from diffusion-limited to drag-off escape using a direct simulation Monte Carlo (DSMC) model developed to simulate planetary atmospheres, referred to as Harrah. A 1D spherically symmetric DSMC model is used to simulate two-component atmospheres to focus on the impact of rarefaction on thermal diffusion. The results for the escape rates and thermal structure are characterized using a mass-averaged Jeans parameter, λ avg,0, and Knudsen number, Kna,0, defined at a reference radial distance r 0. As a test of the model, we simulated the escape of N2 and H2 self-consistently for conditions of Pluto’s upper atmosphere observed during the New Horizons mission. As expected, the DSMC result for H2 escape is consistent with the diffusion-limited approximation, and H2 escape has little effect on the background N2 atmosphere. Then we examined the transition from diffusion-limited to drag-off escape for two-component atmospheres characterized by mass-averaged Knudsen numbers and Jeans parameters of Kna,0 ≈ 0.01–0.1 and λ avg,0 ≈ 0.5–13, respectively. We found that escape transitioned from hydrodynamic escape to an enhanced Jeans-like escape at λ avg,0 ≈ 3.0–3.6. For values of λ avg,0 < 3.0–3.6, escape was hydrodynamic and in the blow-off regime. For values of λ avg,0 >≈ 3.6, the DSMC results indicated that using the diffusion-limited and drag-off approximations can lead to inaccurate estimates of the escape rate.
Source: The Planetary Science Journal
DOI: 10.3847/psj/ada369
Authors: Jack C. Evans, Shane Robert Carberry Mogan, Robert E. Johnson, Orenthal J. Tucker
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,800
Awards: G1453181110, Track 4: Advanced CI Coordination Ecosystem: Monitoring and Measurement Services, G3562386289, Track 1: ACCESS Resource Allocations Marketplace and Platform Services (RAMPS), G4010157413, ACO: An Open CI Ecosystem to Advance Scientific Discovery (OpenCI), Track 3: COre National Ecosystem for CyberinfrasTructure (CONECT), G5367127336, G5464919783, G6423577336, Track 2: Customized Multi-tier Assistance, Training, and Computational Help (MATCH) for End User ACCESS to CI
OpenAlex ID: W4407187305