Establishing a Best Practice for SDTrimSP Simulations of Solar Wind Ion Sputtering

Abstract

Solar wind (SW) ion irradiation on airless bodies can play an important role in altering their surface properties and surrounding exosphere. Much of the ion sputtering data needed for exosphere studies come from binary collision approximation sputtering models such as TRansport of Ions in Matter and its more recent extension, SDTrimSP. These models predict the yield and energy distribution of sputtered atoms, along with the depth of deposition and damage of the substrate, all as a function of the incoming ion type, impact energy, and impact angle. Within SDTrimSP there are several user-specific inputs that have been applied differently in previous SW ion sputtering simulations. These parameters can influence the simulated behavior of both the target and sputtered atoms. Here, we have conducted a sensitivity study into the SDTrimSP parameters in order to determine a best practice for simulating SW ion impacts onto planetary surfaces. We demonstrate that ion sputtering behavior is highly sensitive to several important input parameters including the ion impact angle and energy distribution and the ejected atom surface binding energy. Furthermore, different parameters can still result in similarities in the total sputtering yield, potentially masking large differences in other sputtering-induced behaviors such as the elemental yield, surface concentration, and damage production. Therefore, it is important to consider more than just the overall sputtering behavior when quantifying the importance of different parameters. This study serves to establish a more consistent methodology for simulations of SW-induced ion sputtering on bodies such as Mercury and the Moon, allowing for more accurate comparisons between studies.

Dependences of Energetic Neutral Atoms Energy on the Solar Wind Energy and Solar Zenith Angle Observed by the Chang’E-4 Rover

“…In order to explain the observations, we carry out some numerical simulations with the SDTrimSP code (Szabo et al 2022a). SDTrimSP and its extensions have been widely used to simulate interactions between celestial surfaces and the solar wind (Biber et al 2020;Szabo et al 2022b;Morrissey et al 2023). The elemental composition of lunar soil, obtained from in situ spectral data measured by Chang'E-4, is as follows in terms of atomic percentage: O ∼62.45%, Si ∼17.05%, Fe ∼5.43%, Mg ∼5.09%, Ca ∼5.18%, Al ∼3.05%, and Ti ∼1.76%, respectively (Zhao et al 2023).…”

Backscattering of Ions Impacting Ganymede’s Surface as a Source for Energetic Neutral Atoms

“…Past publications have also discussed the use of different surface binding energies in SDTrimSP (see, e.g., Szabo et al 2020b;Morrissey et al 2022;Jäggi et al 2023;Morrissey et al 2023), but the surface binding energy is a more important parameter for sputtering rather than backscattering due to the lower emission energies of sputtered atoms. We apply the surface binding energy model isbv = 2 (weighted average) with default surface binding energies for water ice, and with an increased O binding for the silicate minerals, as described in Szabo et al (2020b).…”

Energetic Neutral Atom (ENA) Emission Characteristics at the Moon and Mercury From 3D Regolith Simulations of Solar Wind Reflection

“…This approach neglects multibody collisions and overlapping collision cascades, but it has been found to be both accurate and computationally efficient for the energy range of solar wind precipitation (Behrisch & Eckstein, 2007). Several surface properties have to be provided as an input and especially the optimal choice of often unconstrained surface binding energies that affect the sputtering process have been discussed recently (Jäggi et al, 2023;Morrissey et al, 2022Morrissey et al, , 2023Szabo et al, 2020).…”