Reply to comment on "An Active Plume Eruption on Europa During Galileo Flyby E26 as Indicated by Energetic Proton Depletions"

TL;DR

This paper defends the idea that energetic proton depletions observed during Galileo's Europa flyby can be caused by plumes and electromagnetic perturbations, emphasizing the need for careful analysis despite some artefacts in data.

Contribution

It clarifies that proton depletions linked to plumes are still plausible and addresses artefacts and simulation interpretations, reinforcing the significance of plume detection methods.

Findings

Proton depletions can be caused by plumes and electromagnetic fields.

Artefacts in data may result from proton misclassification.

Charge exchange explains certain energy loss observations.

Abstract

In Huybrighs et al., 2020 we investigated energetic proton depletions along Galileo's Europa flyby E26. Based on a particle tracing analysis we proposed that depletions are caused by perturbed electrogmagnetic fields combined with atmospheric charge exchange and possible plumes. One depletion feature identified as a plume signature was shown to be an artefact Jia et al., 2021. Despite that, here we emphasize that Huybrighs et al., 2020 demonstrates that plumes can cause proton depletions and that these features should be sought after. Furthermore, the conclusions on the importance of perturbed electromagnetic fields and atmospheric charge exchange on the depletions are unaffected. We suggest that the artefact's cause is a mistagging of protons as heavier ions by EPD. The artefact prevents us from confirming or excluding that there is a plume associated depletion. We also address comments on the MHD simulations and demonstrate that 540-1040 keV losses are not necessarily inconsistent with 115-244 keV losses by plume associated charge exchange.