Radio emission of the Crab and Crab-like pulsars

Abstract

The pulsar radio emission is commonly associated with the plasma outflow in the open field line tube; then a pencil beam is emitted along the pulsar magnetic axis. Observations suggest that there is an additional radio emission mechanism specific for pulsars with high magnetic field at the light cylinder. These pulsars are known to be strong sources of non-thermal high energy radiation, which could be attributed to reconnection in the current sheet separating, just beyond the light cylinder, the oppositely directed magnetic fields. Pulsars with the highest magnetic field at the light cylinder (> 100 kG) exhibit also radio pulses in phase with the high energy pulses. Moreover, giant radio pulses are observed in these pulsars. I argue that the reconnection process that produces high energy emission could also be responsible for the radio emission. Namely, coalescence of magnetic islands in the sheet produces magnetic perturbations that propagate away in the form of electro-magnetic nanoshots. I estimate the parameters of this emission and show that they are compatible with observations.

Magnetosphere of an orbiting neutron star

“…where B L denotes the magnetic-field strength for the reconnection region, Γ and are the bulk Lorentz factor and characteristic scale of the magnetic islands, D is the distance to the source, and τ ∼ 10/ω p with ω p the plasma frequency. Here, is determined by the force balance and energy conservation in the magnetic islands, and Γ is inferred as 10-100 [28,52]. In the present context, we obtain a quite small flux for orbits close to the innermost stable circular orbit…”

“…The latest work also shows that in the reconnection region, radio waves may be emitted by coalescence of magnetic islands in the CS that produces magnetic perturbations propagating away [28,31,52]. For this process, the predicted spectral flux density of the radio waves with the frequency ν is…”

“…Here we suppose that the total mass of the system is 5.6M , a ≈ 100 km, and the magnetic field strength at the NS pole is B = 10 12 G. We also simply set τ ν = 1. The expected value of in the reconnection region of the pulsar magnetosphere is about 10 times larger than the thickness of the CS, which is proportional to B −3/2 L as [28,52] ∼ 0.1 cm…”

Electromagnetic Precursors to Gravitational-wave Events: Numerical Simulations of Flaring in Pre-merger Binary Neutron Star Magnetospheres

“…Given typically very low efficiency, ≤ 10 −4 , of converting reconnecting magnetic flux into escaping coherent electromagnetic waves it makes it unlikely to expect an FRBstrength radio signal from the current sheet trailing the flare. As noted by Lyubarsky (2020) in a similar context of magnetar flares, reconnection in the collision of the escaping magnetic bubble with the large-scale magnetospheric current sheet is more likely to produce a powerful radio signal. Another coherent radio emission channel is linked to the escaping magnetic bubble.…”

Emission Mechanisms of Fast Radio Bursts

“…The coherent radio emission could be produced during reconnection in magnetically dominated plasma, provided the Larmor radius of particles in the current sheet is comparable with the radio wavelength. This mechanism was recently proposed as a source of radio emission from the Crab and Crab-like pulsars [46][47][48]. In ref.…”