Abstract
Abstract. The aim of this study is to investigate through modelling how sputtering by impacting solar wind ions influences the lifetime of dust particles in the inner heliosphere near the Sun. We consider three typical dust materials, silicate, Fe0.4Mg0.6O, and carbon, and describe their sputtering yields based on atomic yields given by the Stopping and Range of Ions in Matter (SRIM) package. The influence of the solar wind is characterized by plasma density, solar wind speed, and solar wind composition, and we assume for these parameter values that are typical for fast solar wind, slow solar wind, and coronal mass ejection (CME) conditions to calculate the sputtering lifetimes of dust. To compare the sputtering lifetimes to typical sublimation lifetimes, we use temperature estimates based on Mie calculations and material vapour pressure derived with the MAGMA chemical equilibrium code. We also compare the sputtering lifetimes to the Poynting–Robertson lifetime and to the collision lifetime. We present a set of sputtering rates and lifetimes that can be used for estimating dust destruction in the fast and slow solar wind and during CME conditions. Our results can be applied to solid particles of a few nanometres and larger. The sputtering lifetimes increase linearly with the size of particles. We show that sputtering rates increase during CME conditions, primarily because of the high number densities of heavy ions in the CME plasma. The shortest sputtering lifetimes we find are for silicate, followed by Fe0.4Mg0.6O and carbon. In a comparison between sputtering and sublimation lifetimes we concentrate on the nanodust population. The comparison shows that sublimation is the faster destruction process within 0.1 AU for Fe0.4Mg0.6O, within 0.05 AU for carbon dust, and within 0.07 AU for silicate dust. The destruction by sputtering can play a role in the vicinity of the Sun. We discuss our findings in the context of recent F-corona intensity measurements onboard Parker Solar Probe.
Highlights
New observations onboard Parker Solar Probe (PSP) raised interest again in the dust destruction in the vicinity of the Sun
We present a set of sputtering rates and lifetimes that can be used for estimating dust destruction in the fast and slow solar wind and during coronal mass ejection (CME) conditions
This study has investigated dust sputtering during more extreme conditions of coronal mass ejection (CME) events
Summary
New observations onboard Parker Solar Probe (PSP) raised interest again in the dust destruction in the vicinity of the Sun. The observed corona intensity decreases with decreasing PSP distance from the Sun, and this slope changes at 17 solar radii; dust depletion is mentioned as one of the possible explanations for this observation (Howard et al, 2019). Parker Solar Probe (Fox et al, 2016) and Solar Orbiter (Müller et al, 2013) will help to quantify the dust component in the inner heliosphere with unprecedented detail. These spacecraft do not carry dedicated dust sensors but can measure the dust component from the F-corona intensity as mentioned above and detect high-velocity dust impacts on the satellite body using electric field sensors. The dust impacts are observed because they change the floating potential of the spacecraft for short periods of time (see e.g. Zaslavsky, 2015)
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