Transparency of Fast Radio Burst Waves in Magnetar Magnetospheres

Abstract

At least some fast radio bursts (FRBs) are produced by magnetars. Even though mounting observational evidence points towards a magnetospheric origin of FRB emission, the question of the location for FRB generation continues to be debated. One argument suggested against the magnetospheric origin of bright FRBs is that the radio waves associated with an FRB may lose most of their energy before escaping the magnetosphere because the cross-section for $e^{\pm }$ to scatter large-amplitude EM waves in the presence of a strong magnetic field is much larger than the Thompson cross-section. We have investigated this suggestion and find that FRB radiation traveling through the open field line region of a magnetar's magnetosphere does not suffer much loss due to two previously ignored factors. First, the plasma in the outer magnetosphere ($r \gta 10^9 \ $cm), where the losses are potentially most severe, is likely to be flowing outward at a high Lorentz factor ${\gamma }_p\ge 10^3$. Second, the angle between the wave vector and the magnetic field vector, ${\theta }_B$, in the outer magnetosphere is likely of the order of 0.1 radian or smaller due in part to the intense FRB pulse that tilts open magnetic field lines so that they get aligned with the pulse propagation direction. Both these effects reduce the interaction between the FRB pulse and the plasma substantially. We find that a bright FRB with an isotropic luminosity $L_{\rm frb} \gta 10^{42} \ {\rm erg \ s^{-1}}$ can escape the magnetosphere unscathed for a large section of the ${\gamma }_p-{\theta }_B$ parameter space, and therefore conclude that the generation of FRBs in magnetar magnetosphere passes this test.

12 pages, 9 figures. Updated version with more precise calculations

References in corpus (14)

• A bright millisecond radio burst of extragalactic origin
• Fast radio bursts as synchrotron maser emission from decelerating relativistic blast waves
• INTEGRAL discovery of a burst with associated radio emission from the magnetar SGR 1935+2154
• The Physical Mechanisms of Fast Radio Bursts
• A bimodal burst energy distribution of a repeating fast radio burst source
• Diverse polarization angle swings from a repeating fast radio burst source
• Implications of a "Fast Radio Burst" from a Galactic Magnetar
• Fast radio bursts and their high-energy counterpart from magnetar magnetospheres
• Coherent inverse Compton scattering by bunches in fast radio bursts
• Magnetospheric curvature radiation by bunches as emission mechanism for repeating fast radio bursts
• Polarization properties of FRB 20201124A from detections with the 100-m Effelsberg Radio Telescope
• Coherent Electromagnetic Emission from Relativistic Magnetized Shocks
• Can a strong radio burst escape the magnetosphere of a magnetar?
• Electrodynamics of Magnetars IV: Self-Consistent Model of the Inner Accelerator, with Implications for Pulsed Radio Emission

Cited by in corpus (18)

• The Physics of Fast Radio Bursts
• Polarization of Fast Radio Bursts: radiation mechanisms and propagation effects
• Faraday Rotation Measure Variations of Repeating Fast Radio Burst Sources
• Polarisation of magnetospheric curvature radiation in repeating fast radio bursts
• Direct Emission of Strong Radio Pulses During Magnetar Flares
• Expanding Fireball in Magnetar Bursts and Fast Radio Bursts
• Escape of fast radio bursts from magnetars
• Multi-wavelength and Multi-messenger Counterparts of Fast Radio Bursts
• The plasma suppression effect can be ignored in realistic FRB models invoking bunched coherent radio emission
• Constraining the FRB mechanism from scintillation in the host galaxy
• Hyper-active repeating fast radio bursts from rotation modulated starquakes on magnetars
• Fast Radio Bursts with Narrow Beaming Angles Can Escape from Magnetar Magnetospheres
• Scattering Cross Sections of Magnetized Particles within Intense Electromagnetic Waves: Application to Fast Radio Bursts
• Fast Radio Bursts from non-resonant Alfvén waves and synchrotron maser emission in the magnetar wind
• Evidence of the association of repeating fast-radio-burst sources with fast-spinning super-twisted magnetars
• Circular polarization of fast radio bursts by asymmetric erosion in longitudinally magnetized plasma
• Electromagnetic Precursors to Binary Neutron Star Mergers: Kinetic Simulations of Magnetospheric Flaring
• The Impact of Accretion on FRB Radiation Mechanisms in Binary Systems: Constraints and Implications