In the Atmospheric Discharges group we study the occurrence and effects of electricity in our atmosphere. The enormous electric fields associated with lightning make it difficult to observe in-situ, and our research employs both analysis of data (primarily from the Atmosphere-Space Interactions Monitor, ASIM, on the ISS) and computational simulation.
My research focuses on computer simulations of Terrestrial Gamma-Ray Flashes (TGFs), bursts of X- and gamma-rays released to space in connection with lightning strikes. As both X- and gamma-rays lie outside of the visible spectrum, TGFs were not discovered until 1994, and the mechanisms associated with them are still unclear. For an electron to produce a gamma-photon by the Bremsstrahlung process, it must first be accelerated to relativistic speeds by an exceptionally strong electric field. Even in connection with thunderstorms, the correct conditions have yet to be observed.
We theorise that the specific geometry of hydrometeors (ice and water particles suspended in the atmosphere) can locally enhance the electric field sufficiently for gamma-photon Bremsstrahlung to take place. To this end, a computer simulation is produced, where we track millions of electrons (among other particles) in flight through an electric field. In this way we can observe their behaviour and the development of the lightning process and TGF mechanisms. As large numbers of electrons are computationally heavy to trace, our simulation is GPU-based and hybrid, to simulate electrons both as particles and as fluids, in the plasma interior. It is also optimised for the newest generation of pre-exascale supercomputers.
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