Abstract
AbstractComputation of the ionization and radiation dose in arbitrary (exo‐) planetary atmospheres due to energetic particles is recently becoming more important due to several reasons that are either correlated with the detection of trace gases for life on exoplanets or with computing dose rates at arbitrary altitudes in the Earth atmosphere. We previously presented Atmospheric Radiation Interaction Simulator, a new Geant4‐based code tailored specifically to enable parametric studies of radiation propagation through exoplanetary atmospheres (Banjac et al., 2019 https://doi.org/10.1029/2018JA026042). Therein, the calculation of ion‐electron pair production rates, which are a mandatory input for chemical and atmospheric modeling, has been presented and validated against Earth measurements and also other, similar, but solar‐system‐specific Geant4‐based codes (PLANETOCOSMICS). In addition to providing input for atmospheric modeling of exoplanets, with AtRIS we aim to directly characterize the habitability by calculating the absorbed dose. In this technical validation study, after showing a detailed analysis of the secondary particles contributing to the atmospheric radiation, we describe a feature of the code which makes direct parametric studies of the interrelation of incident radiation and the resulting absorbed dose throughout the atmosphere possible. In a validation case study configured using an atmospheric model obtained with NRLMSISE‐00 and a primary proton and helium GCR flux calculated using a recent improvement of the force‐field approach, we have compared simulation results with measurements obtained with the Flight Radiation Environment Detector (FRED). We show that Atmospheric Radiation Interaction Simulator (AtRIS) can reproduce the measured dose rate dependence on altitude.
Highlights
When energetic particles pass through matter, they interact in several ways
In addition to providing input for atmospheric modeling of exoplanets, with Atmospheric Radiation Interaction Simulator (AtRIS) we aim to directly characterize the habitability by calculating the absorbed dose. In this technical validation study, after showing a detailed analysis of the secondary particles contributing to the atmospheric radiation, we describe a feature of the code which makes direct parametric studies of the interrelation of incident radiation and the resulting absorbed dose throughout the atmosphere possible
We show that Atmospheric Radiation Interaction Simulator (AtRIS) can reproduce the measured dose rate dependence on altitude
Summary
When energetic particles pass through matter, they interact in several ways. While the most dominant interaction mechanism is of electromagnetic nature, especially at higher energies, nuclear interactions become more significant. In order to achieve its objectives, that is, to calculate the atmospheric ion-electron pair production rate as well as the absorbed and equivalent radiation dose, the primaries and the resulting secondaries are tracked throughout the planetary model. One would have to determine the energy and angular distributions of all secondary particles and use this as input for a separate simulation in which a phantom is irradiated This approach, has many disadvantages such as, for example, (i) the AtRIS simulation (mode 0, see Banjac et al, 2019, Appendix A) that provides the necessary information about secondary particles could result in several terabytes of data, (ii) the post processing would include many error-prone steps, and (iii) for each atmospheric shell interface, a separate simulation would need to be performed. Note that the calculation of the absorbed dose aims to help in characterizing the habitability of an exoplanet and has no direct relevance for the detection of biosignatures
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