non-thermal Radiation from AStrophysical jets: from theory of Plasma turbulence to Observations

ended

"Relativistic jets from Active Galactic Nuclei (AGN) and Gamma Ray Bursts (GRBs) have fascinated astronomers for decades. Despite its importance for multi-messenger astronomy, astroparticle physics, and galaxy evolution, the physics of relativistic jets is not fully understood. According to a widely accepted paradigm, relativistic jets extract the rotational energy of the black hole via electromagnetic stresses, and transport it out to large distances in the form of Poynting flux. However, we do not understand how the Poynting flux is converted into the non-thermal radiation that we observe. Since relativistic jets have huge Reynolds numbers, turbulence could naturally dissipate the magnetic energy and accelerate a population of non-thermal particles, which emit the observed radiation via synchrotron and inverse Compton cooling. Developing concrete jet emission models based on such scenario has recently become possible due to the advent of large-scale fully kinetic simulations of magnetically dominated plasma turbulence. A crucial finding of these simulations is that particles have a strong pitch angle anisotropy (namely, particles move nearly along the direction of the local magnetic field), contrary to the textbook (and ad hoc) assumption that the radiating particles in relativistic jets are isotropic. I propose a project aiming to investigate ""non-thermal Radiation from AStrophysical jets: from theory of Plasma turbulence to Observations"" (RASPO). In this project, I will develop models for the pitch angle and energy distribution of the radiating particles that rely on fully kinetic simulations (rather than ad hoc assumptions), and fit these model to the non-thermal spectra of AGN and GRB jets. I will study the apparent contradiction between fitting of non-thermal spectra with existing isotropic models, which suggest that the emission region is matter dominated, and theoretical expectations, which suggest that jets should be instead magnetically dominated objects."