Computational study of discharges

This branch of the group “Electric discharges in the Atmosphere” focuses on the computational study of streamer discharges, lightning leaders and associated phenomena such as terrestrial gamma-ray flashes (TGFs) as well as the chemistry of greenhouse gases and (pre-)biotic molecules in various gas mixtures.

TGFs are bursts of high-energy photons (MeV) from thunderstorms making them the most energetic natural phenomena on Earth; however, we are still lacking fundamental knowledge about their production mechanism and their effects. This research is embedded in the DFF Sapere Aude Starting Grant project “Relativistic electrons and terrestrial gamma-ray flashes from lightning” which aims at understanding the emission and effects of terrestrial gamma-ray flashes (TGFs) in and above thunderclouds on Modern and Primordial Earth.

The research objectives are to determine the:

• Processes producing relativistic electrons and TGF photons, and assess the role of hydrometeors in the production of discharges creating high electric fields for electron acceleration
• Significance of relativistic particles on the production of greenhouse gases
• Influence of relativistic particle beams from thunderstorms on the production of (pre-)biotic molecules in the atmosphere of Primordial Earth

The research group develop and employ particle-in-cell Monte Carlo, fluid and hybrid models to study various aspects of discharges, understand streamers and leaders as well as TGFs and their implications. Particle-in-cell models treat individual particles (electrons/leptons, photons, hadrons) allowing to study their physics thoroughly and account for rare events. Fluid models treat discharges as a fluid and update particle densities only which makes them computationally fast. Hybrid models combine these two worlds in order to combine the accuracy of particle models with the computational efficiency of fluid models. Additionally, we want to couple these models to plasma chemistry models allowing us to study how electrons and photons activate the ambient gas triggering the chemistry towards greenhouse gases and pre-biotic molecules.

A main part of this research is to adapt and extend these models to the architectures of the newest generation of pre-exascale supercomputers (e.g. LUMI) in order to exploit macroscale simulations (as never before) in the future and to extend our models to astrophysical plasma phenomena.

We collaborate with colleagues at various national and international institutes, e.g. DTU Physics, DTU Compute, the University of Belgrade and the Alabama A&M University.