Master Projects With Prof. Mertsch (2020-2021)


Project 1: The acceleration of charged dark matter in supernova remnants

Context: If a fraction of dark matter carries an electric charge, the dark matter particles could be accelerated by the sources of ordinary cosmic rays, that is supernova remnants. The details of the acceleration and the subsequent transport through the Galaxy depend on the charge and mass of the dark matter particles and thus provide a new test bed for dark matter searches.

Goals: We will characterise the importance of various processes at work that is acceleration, energy losses, escape and feedback onto the plasma. The central piece of this project will be the prediction of the fluxes of charged dark matter in a terrestrial detector. We will then set bounds on the dark matter properties by using both, constraints from direct searches and observations of ordinary cosmic rays.

Methods: Initially, we will perform analytical estimates and rely on results from semi-analytical methods. As non-linearities can become important, we will ultimately make use of numerical methods.

Prerequisites: Some familiarity with basic basic plasma physics and coding is most welcome.

Project 2: Small-scale anisotropies and the turbulent nature of the interstellar medium

Context: The transport of cosmic rays in the Galaxy is mostly diffusive, thus washing out almost all directional information. Yet, a few years ago, anisotropies were discovered in the arrival directions of cosmic rays. To understand this new phenomenon, one must understand the relative diffusion of pairs of particles through turbulent magnetic fields. Comparing predictions with observations allows for deeper insights into the turbulent nature of the interstellar medium.

Goals: We will predict observables like the angular power spectrum, starting from first-principle electrodynamics and working with contemporary models of magnetised turbulence. A particular focus could be on the energy-dependence and we would like to find model parameters that are compatible with the observed angular power spectra.

Methods: We will be working mostly analytically. For cross-checks, we can reuse numerical results that my group is presently working on.

Prerequisites: You should be keen to learn about cosmic rays and should have a hand for solving problems analytically.

Project 3: High-energy neutrinos from blazars

Context: Blazars are the dominant sources of high-energy gamma-rays in the extra-galactic sky. Reconnection through so-called plasmoids offers an interesting and predictive model for the origin of their non-thermal emission. The comparison with time-resolved data opens up a new window for understanding the physics of these most violent accelerators.

Goals: We will investigate temporal correlations in the plasmoid model, both auto-correlations, but also cross-correlation between different wavelengths (e.g. between radio and gamma-rays) or different messengers (e.g. between gamma-rays and high-energy neutrinos). We will apply our findings to the recently observed neutrino emission from the blazar TXS 0506+056.

Methods: We will be building on existing codes, both for the statistics of the plasmoids and for the radiation modelling.

Prerequisites: Some coding skills and an interest in statistical analysis.