Macroscopic modelling of radio emission from ultra-high-energy-cosmic-ray-induced air showers

PhD ceremony: Mr. K.D. de Vries, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Macroscopic modelling of radio emission from ultra-high-energy-cosmic-ray-induced air showers

Promotor(s): prof. O. Scholten, prof. K. Werner

Faculty: Mathematics and Natural Scineces

When an ultra-high-energy cosmic ray collides in Earth's atmosphere it induces a cascade of secondary particles flying toward Earth's surface with approximately the speed of light. A net electron excess in combination with the deflection of electrons and positrons in Earth's magnetic field gives rise to large electric currents in the particle cascade. The radio emission due to the time variation of these currents in combination with relativistic effects is calculated. Especially relativistic “Cherenkov” effects due to the finite density of air are shown to be crucial in the description of the radio emission.

To model the radio emission a computer code has been developed. This code uses the charge and current distributions in the particle cascade as obtained directly from Monte-Carlo simulations. These distributions are used to calculate the radio emission. Results from simulations show that radio emission is an excellent probe to obtain information about the mass and composition of the initial cosmic ray. Furthermore, a comparison of the simulations with data is given and for the first time in a natural process strong indications are found for the emission due to the net electron excess in the particle cascade.