Dynamics of radiating particles in current sheets with a transverse magnetic field component

Abstract

Upcoming multipetawatt laser facilities are capable of inducing effects of quantum electrodynamics (QED) in laser-plasma interaction such as strong radiation reaction and QED cascades, both of which can significantly influence the properties and dynamics of laser plasma. This can result in the formation of extreme plasma structures with unprecedented TG levels of quasistatic magnetic fields, for example current sheets or pinch configurations of nanometer scale or smaller. In such structures radiation losses can play a significant role, so the influence of radiation losses onto the evolution of extreme current sheets deserves a separate and thorough investigation. In the current work we develop an analytical model and extend the quasiadiabatic approach describing individual particle motion onto 3D particle motion in the case when radiation reaction is non-negligible. Given that particle motion is determined by (quasi)invariants of non-dissipative motion, we derive how these (quasi)invariants evolve under the influence of radiation losses, quantify this influence and obtain a (quasi)invariant of dissipative motion. This allows reducing the dimensionality of the system of differential equations describing particle motion to just two instead of six. It is also discussed how the presented method can be used in a wider range of problems.