Speaker
Description
Fast Radio Bursts (FRBs) are short, intense bursts of radio waves (100 MHz-10 GHz) lasting between 4 μs - 10 ms. These bursts, with typical luminosities of order 10^41 erg/s, have been detected at cosmological distances up to redshift z=2.1. Their extreme energetics and great brevity lead to unphysically high brightness temperatures (around 10^37 K), which implies a coherent emission mechanism.
A lot more has become known about these mysterious FRBs since their discovery in 2007. Thanks to tremendous efforts on improved instrumentation, some ~5000 FRBs have been detected by now. A further breakthrough came with the discovery of an FRB-like burst from the Milky Way magnetar SGR 1935+2154, thus firmly establishing the FRB-magnetar connection.
Despite these advances in observational knowledge, a theoretical consensus on how FRBs are generated is still far away. Generation models can generally be grouped into two groups: those where the radio waves are generated within the inner magnetosphere (r < 10^10 cm), and those were radio waves are released further away in the magnetar wind and beyond [1,2]. Both types of models face problems: the 'far-field' models struggle to explain the short timescales (< 100 ns) displayed by FRBs, whereas 'near-field' models have to explain how the radio waves can escape the obstructing inner regions of the magnetar magnetosphere. [3]
In this talk we zoom into this so-called "Fast Radio Burst Escape Problem". At first we give a general discussion of the FRB escape problem, and then present a novel set of simulations of the interaction between magnetised particles and strong electromagnetic waves. We argue that the stochastic acceleration processes which can kill an FRB still occur under a wide range of magnetic field obliqueness angles. Finally, we demonstrate that the parameter space of strong electromagnetic waves under which stochastic acceleration processes can occur exhibits unexpected fractal properties.
[1] "Emission Mechanisms of Fast Radio Bursts", Y. Lyubarsky (2021).
[2] "Solving the Mystery of Fast Radio Bursts: A Detective's Approach", B. Zhang (2023).
[3] "Scattering of Ultrastrong Electromagnetic Waves by Magnetized Particles", A.M. Beloborodov (2022).