Magnetocentrifugal acceleration of bulk motion of plasma in pulsar magnetosphere

TL;DR

This paper investigates how magneto-centrifugal forces can accelerate plasma in pulsar magnetospheres, showing that twisted magnetic field lines can boost particles to energies explaining observed very high energy gamma-ray emissions.

Contribution

It demonstrates that twisted magnetic field lines in pulsar magnetospheres can efficiently accelerate plasma via magneto-centrifugal forces, aligning with recent numerical models.

Findings

Lorentz factor increases with radius as γ∼(1-(rΩ/c)^2)^{-1}

Magneto-centrifugal acceleration can produce energies explaining VHE gamma-rays from Crab pulsar

Existence of twisted field lines near the last closed field line in pulsar magnetospheres

Abstract

Acceleration of bulk motion of plasma due to magneto centrifugal mechanism is investigated for different shapes of the field lines of 3-D magnetic field. It is shown that this mechanism can be efficient provided that the field line is twisted into direction of rotation. According to the last results of the numerical modelling a fraction of the field lines with such geometrical shape apparently exist in the pulsar magnetosphere close to the last closed field line. In this case the Lorentz factor $\gamma$ increases with the radius $r$ along these field lines as $\gamma\sim (1-(r\Omega/c)^2)^{-1}$, where $\Omega$ - angular velocity of the pulsar rotation. The magneto centrifugal mechanism provides acceleration of the electrons to the energy which is sufficient to explain the observed VHE pulsed $\gamma$-rays from Crab pulsar.