Global Climate Model Occultation Lightcurves Tested by August 2018 Ground-Based Stellar Occultation

TL;DR

This study tests Pluto's 3D climate model predictions against actual stellar occultation data from August 2018, revealing the importance of N2 ice distribution and haze effects on observed lightcurves.

Contribution

It introduces a Fourier optics-based method to generate model lightcurves from 3D GCM atmospheric data and compares these with real occultation observations.

Findings

Best-fit climate scenario includes N2 ice in southern hemisphere.

Haze reduces central flash strength in lightcurves.

Lower P/T ratio causes anomalies in central flash shoulders.

Abstract

Pluto's atmospheric profiles (temperature and pressure) have been studied for decades from stellar occultation lightcurves. In this paper, we look at recent Pluto Global Climate Model (GCM) results (3D temperature, pressure, and density fields) from Bertrand et al. (2020) and use the results to generate model observer's plane intensity fields (OPIF) and lightcurves by using a Fourier optics scheme to model light passing through Pluto's atmosphere (Young, 2012). This approach can accommodate arbitrary atmospheric structures and 3D distributions of haze. We compared the GCM model lightcurves with the lightcurves observed during the 15-AUG-2018 Pluto stellar occultation. We find that the climate scenario which best reproduces the observed data includes an N2 ice mid-latitude band in the southern hemisphere. We have also studied different haze and P/T ratio profiles: the haze effectively reduces the central flash strength, and a lower P/T ratio both reduces the central flash strength and incurs anomalies in the shoulders of the central flash.