Pulsar current sheet Cerenkov radiation

TL;DR

This paper proposes that Cerenkov radiation from current sheets in pulsar magnetospheres could explain observed radio signals, highlighting a novel coherent emission mechanism driven by ultra-relativistic particles.

Contribution

It introduces a new model where current sheet Cerenkov radiation accounts for pulsar radio emissions, connecting plasma physics with observable signals.

Findings

Cerenkov radiation can occur in pulsar current sheets under specific plasma conditions.

The mechanism potentially explains key features of pulsar radio signals.

The model aligns with known plasma frequencies and magnetic field strengths in pulsars.

Abstract

Plasma-filled pulsar magnetospheres contain thin current sheets wherein the charged particles are accelerated by magnetic reconnections to travel at ultra-relativistic speeds. On the other hand, the plasma frequency of the more regular force-free regions of the magnetosphere rests almost precisely on the upper limit of radio frequencies, with the cyclotron frequency being far higher due to the strong magnetic field. This combination produces a peculiar situation, whereby radio-frequency waves can travel at subluminal speeds without becoming evanescent. The conditions are thus conducive to Cerenkov radiation originating from current sheets, which could plausibly serve as a coherent radio emission mechanism. In this paper we aim to provide a portrait of the relevant processes involved, and show that this mechanism can possibly account for some of the most salient features of the observed radio signals.