Radiation-dominated particle and plasma dynamics

Artikel i vetenskaplig tidskrift, 2018

We consider charged particle motion in a strong electromagnetic field of an arbitrary configuration and find a universal behaviour: for sufficient field strengths, the radiation losses lead to a general tendency of the charge to move along the direction that locally yields zero acceleration orthogonal to the direction of motion. This corresponds to the suppression of radiation losses according to both classical and quantum considerations. We show that such a radiation-free direction (RFD) exists at each point of an arbitrary electromagnetic field, while the time-scale of approaching this direction decreases with the increase in field strength. In the case of a sufficiently strong electromagnetic field, at each point of space, the charges mainly move and form currents along the local RFD, while the deviation of their motion from RFD can be calculated to determine their incoherent emission. This forms a general description of particle, and therefore plasma, dynamics in strong electromagnetic fields, the latter being generated by state-of-the-art lasers or in astrophysical environments.