Absorption of Gamma-Ray Photons in a Vacuum Neutron Star Magnetosphere: II. The Formation of "Lightnings"

TL;DR

This paper models how high-energy gamma-ray photons trigger lightning-like plasma structures in neutron star magnetospheres, potentially explaining short radio bursts observed as RRATs.

Contribution

It introduces a detailed physical model of lightning formation in neutron star magnetospheres, linking gamma-ray absorption to plasma generation and radio emission.

Findings

Lightning propagates at near light speed along magnetic field lines.

Electron-positron pair production reaches up to 10^28 in a lightning event.

Formed plasma densities are comparable to pulsar polar caps.

Abstract

The absorption of a high-energy photon from the external cosmic gamma-ray background in the inner neutron star magnetosphere triggers the generation of a secondary electron-positron plasma and gives rise to a lightning - a lengthening and simultaneously expanding plasma tube. It propagates along magnetic fields lines with a velocity close to the speed of light. The high electron-positron plasma generation rate leads to dynamical screening of the longitudinal electric field that is provided not by charge separation but by electric current growth in the lightning. The lightning radius is comparable to the polar cap radius of a radio pulsar. The number of electron-positron pairs produced in the lightning in its lifetime reaches 10^28. The density of the forming plasma is comparable to or even higher than that in the polar cap regions of ordinary pulsars. This suggests that the radio emission from individual lightnings can be observed. Since the formation time of the radio emission is limited by the lightning lifetime, the possible single short radio bursts may be associated with rotating radio transients (RRATs).