The coughing pulsar magnetosphere

Abstract

Polar magnetospheric gaps consume a fraction of the electric potential that develops accross open field lines. This effect modifies significantly the structure of the axisymmetric pulsar magnetosphere. We present numerical steady-state solutions for various values of the gap potential. We show that a charge starved magnetosphere contains significantly less electric current than one with freely available electric charges. As a result, electromagnetic neutron star braking becomes inefficient. We argue that the magnetosphere may spontaneously rearrange itself to a lower energy configuration through a dramatic release of electromagnetic field energy and magnetic flux. Our results might be relevant in understanding the recent December 27, 2004 burst observed in SGR 1806-20.

Electrodynamics of Pulsar Magnetospheres

“…The force-free magnetosphere of the aligned rotator (Ω µ) is described by the poloidal flux function Ψ (r, θ) that obeys the pulsar equation (Equation 11) with the boundary condition Equation (22). This equation was solved numerically by Contopoulos et al (1999) (see also Goodwin et al 2004;Gruzinov 2005;Contopoulos 2005;Timokhin 2006). The solution gives the poloidal magnetic field B P (which determines the charge density ρ GJ = −Ω · B P /2πc) and the self-consistent poloidal current J P (which determines B φ ).…”

Pulsar State Switching From Markov Transitions and Stochastic Resonance

“…However, the stochastic resonance model for the quasiperiodicity in B1931+24 suggests the action of a ∼38 day period forcing function that is easiest to understand as modulation of the return current from a region outside the light cylinder. Equatorial current sheets that are disk-like are a common feature in recent numerical simulations of pulsar magnetospheres for aligned rotators (Krause-Polstorff & Michel 1985;Contopoulos 2005;Timokhin 2010;Kalapotharakos et al 2012;Li et al 2012aLi et al , 2012b. Equatorial disks are prominent in charge-starved cases (Michel 1980) that are electromagnetically "dead."…”

“…Dramatic changes of magnetospheric structure by pulsar-disk interactions were a conclusion of Barsukov et al (2009). Recent magnetosphere models incorporate a "Y" point where current from the current sheet flows along the separatrix to both magnetic PCs (e.g., Contopoulos 2005;Timokhin 2006). This feature may provide the most direct feedback from a pulsar's environment to its PCs.…”

“…Some of these may be stochastic and others periodic. In addition, magnetic reconnection within the disk from magnetic fields with oppositive polarities above and below the disk can inject relativistic particles into the magnetosphere (e.g., Contopoulos 2005;Komissarov 2006;Timokhin 2006).…”

Force-free magnetosphere of an aligned rotator with differential rotation of open magnetic field lines

“…In these works the angular velocity of plasma rotation was assumed to be constant, although the case when the open field lines rotate with a constant angular velocity different from the angular velocity of the Neutron Star (NS) was addressed in some works (see e.g. Contopoulos 2005;Beskin & Malyshkin 1998). It was also implicitly assumed that the current density in the magnetosphere could adjust to any distribution required by the global structure of the magnetosphere.…”