SMuK 2023 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 13: Astrophysics: Galaxies II

EP 13.3: Talk

Thursday, March 23, 2023, 18:15–18:30, ZEU/0160

Improved numerical scheme for solving shock acceleration in jets using stochastic differential equations — •Patrick Günther, Sarah Wagner, and Karl Mannheim — Institute for Theoretical Physics and Astrophysics, University of Würzburg

Supersonic jets ejected from active galactiv nuclei show in situ acceleration of charged particles to ultrarelativistic energies far away from the central black hole. Diffusive shock acceleration and momentum diffusion, also known as 1st and 2nd order Fermi acceleration, are mechanisms that can explain the observed particle spectra. In the test-particle and diffusion approximation regime, the governing transport equations are Fokker-Planck equations equivalent to stochastic differential equations which can be solved numerically in a fast way. Advantages and disadvantages of this Monte-Carlo sampling method are discussed. The accuracy of the results depends on the choice of the numerical integrator used and a number of schemes are tested and compared. Basic integrators like the Cauchy-Euler scheme fail to predict the acceleration accurately in a scenario with steep shock gradients. It is shown that a semi-implicit second-order scheme can remedy this problem allowing for using the method in hybrid magnetohydrodynamical jet simulations in order to predict their non-thermal emissions.