Escaping of Fast Radio Bursts

Abstract

We reconsider the escape of high brightness coherent emission of Fast Radio Bursts (FRBs) from magnetars' magnetospheres, and conclude that there are numerous ways for the powerful FRB pulse to avoid nonlinear absorption. Sufficiently strong surface fields, $\geq 10\%$ of the quantum field, limit the waves' non-linearity to moderate values. For weaker fields, the electric field experienced by a particle is limited by a combined ponderomotive and parallel-adiabatic forward acceleration of charges by the incoming FRB pulse along the magnetic field lines newly opened during FRB/Coronal Mass Ejection (CME). As a result, particles surf the weaker front part of the pulse, experiencing low radiative losses, and are cleared from the magnetosphere for the bulk of the pulse to propagate. We also find: (i) for propagation across magnetic field, the O-mode suffers much smaller dissipation than the X-mode; (ii) quasi-parallel propagation suffers minimal dissipation; (iii) initial mildly relativistic radial plasma flow further reduces losses; (iv) for oblique propagation of a pulse with limited transverse size, the leading part of the pulse would ponderomotively sweep the plasma aside.