On the origin and physics of Gamma Flares in Crab Nebula

TL;DR

This paper proposes a mechanism where pulsar energy converts into Langmuir waves, leading to plasma instabilities and particle acceleration, which may explain gamma-ray flares in the Crab Nebula, especially around 100 MeV.

Contribution

It introduces a novel model linking pulsar magnetosphere processes to gamma-ray flares via Langmuir wave dynamics and self-trapping of synchrotron radiation.

Findings

Energy transfer from pulsar to nebula via plasmon condensate is efficient.

Langmuir wave collapse can accelerate particles, causing flares.

Self-trapping of radiation explains energy-specific flare observations.

Abstract

We consider parametric generation of electrostatic waves in the magnetosphere of the pulsar PSR0531. It is shown that in the framework of this mechanism it is possible to convert the pulsar rotational energy into the energy of Langmuir waves. The maximum growth rate is achieved in the "superluminal" area, where phase velocity of perturbations is exceeding the speed of light. Therefore electromagnetic waves do not damp on particles. Instead, they create plasmon condensate, which is carried out, outside of the pulsar magnetosphere and reaches the Crab nebula. It is shown, that the transfer of the energy of the plasmon condensate from the light cylinder to the active region of the nebula happens practically without losses. Unlike the plasma of the magnetosphere, the one of nebula contains ions, i.e., it may sustain modulation instability, which leads to the collapse of the Langmuir condensate. Langmuir wave collapse, in turn, leads to the acceleration of the distribution function particles. Furthermore, we consider processes leading to the self-trapping of the synchrotron radiation, resulting in the growth of the radiation intensity, which manifests itself observationally as a flare. The condition for the self-trapping onset is derived, showing that if the phenomena takes place at $~100 MeV$, then it doesn't happen at lower (or higher) energies. This specific kind of higher/lower energy cutoff could explain why when we observe the flare at 100 MeV no enhanced emission is observed at lower/higher energies!