A numerical approach to calculate cross sections for relativistic electrons and terrestrial gamma-ray flashes
Description
Terrestrial gamma-ray flashes (TGFs) are bursts of energetic X- and gamma-rays which are emitted from thunderstorms as the Bremsstrahlung of relativistic electrons. While such relativistic particles propagate through the atmosphere, they interact with air molecules which can be studied with particle Monte Carlo models. Such models require cross sections as an input. Whilst there are well established data for elastic scattering, Bremsstrahlung and impact ionization through relativistic electrons as well as for photoionization, Compton scattering and pair production for energetic photons, we lack cross sections for photoexcitation, photodissociation or the excitation of air molecules through electrons which can contribute to the chemical activation of the atmosphere, potentially relevant for the study of greenhouse gas production from lightning in our atmosphere. In order to fill this cross section gap, we here present a novel numerical tool calculating cross sections directly from Feynman diagrams providing both differential and total cross sections. We provide an overview of the code structure and present benchmarking cases against well-known cross sections. Additionally, we will present a first application by calculating the cross section for photodissociation for a wide range of energies. The presented model is capable of calculating cross sections for more leptonic and photonic processes in the atmosphere than today. Subsequently, this will allow for more realistic simulations of energetic phenomena in our atmosphere.