The Origin of Strong Linear Polarization from Fast Radio Bursts

Abstract

The detection of almost 100% linearly polarized emission from the fast radio burst source FRB 121102 implies coherent emission of relativistic electrons moving perpendicular to the ambient magnetic field. The origin of such a particle distribution is very intriguing. Given that FRB 121102 is likely driven by a neutron star, we explored orbits of charged particles trapped in a dipole magnetic field (the Störmer problem). Most previous studies focused on particles with relatively low energies so that the guiding center approximation may be applied. High-energy particles usually have chaotic orbits except those on a periodic orbit or near stable periodic orbits. Via evaluation of the maximum Lyapunov exponent of orbits of particles launched from the equatorial plane with an axial velocity (the angular velocity sets the length and energy scales of the system), we found prominent regions of quasi-periodic orbits around stable periodic orbits in the equatorial plane at high energies. Particles in these orbits oscillate around the equatorial plane and their radial distance from the dipole can vary by a factor of ∼2. Relativistic electrons in such orbits may be responsible for the almost 100% polarized emission from FRB 121102.

A Search for Coincident Neutrino Emission from Fast Radio Bursts with Seven Years of IceCube Cascade Events

“…Recently, FRB 200448 was localized to the Galactic magnetar SGR 1935+2154, suggesting magnetars may be a source of FRBs (Anderson et al 2020). This has been further supported by the polarization of some FRBs (Wang et al 2021). While the underlying mechanism that creates FRBs is unknown, it is predicted that this coherent radio emission is the result of an ultrarelativistic shock that propagates into a baryon-filled medium.…”

Orbits of charged particles with an azimuthalinitial velocity in a dipole magnetic field

“…In particular, significant efforts have been put to study periodic orbits in the Meridian plane [8][9][10][11][12], and it has been known that stable periodic orbits can affect statistical properties of the whole system significantly [2,4]. Stable periodic orbits also bear significance in physical systems since their associated stable quasi-periodic orbits can be realized and have distinct characteristics [13,14].…”