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Pulsar Winds

Pulsars are rapidly rotating, magnetized neutron stars, and all those not in a binary star system are observed to be slowing down. Charged particles (most likely electrons and positrons) and magnetic fields carry the rotation energy away from the star in a relativistic wind, and deposit it in a ”nebula” observed in the radio, optical, X-ray and gamma-ray wavebands around several pulsars.

However, how the energy is released is unknown. One possibility is magnetic reconnection or annihilation. The pulsar wind carries a wave pattern imprinted on it at the rotation frequency of the star. Magnetic field lines from the two poles are folded into a striped pattern, separated by a current sheet. The alternating component of the field can be dissipated in the sheet, leading to heating and acceleration of the wind. If it occurs rapidly, dissipation will give pulsed high energy emission, similar to that observed.

The current sheet in the wind surrounding a pulsar, sketched from an analytic solution for the relativistic magnetohydrodynamic flow. As the star rotates, the pattern moves radially outwards at a speed close to that of light. Across the sheet, the direction of the magnetic field reverses. Magnetic field dissipation leads to heating of the plasma in the sheet.

The polarisation properties of pulsed optical emission from the Crab pulsar as predicted in the striped-wind model (left) and as observed (right). The radiation intensity, the polarised fraction, and the angle of linear polarisation are shown.


Recent contributions

Takamoto, Makoto; Kisaka, Shota; Suzuki, Takeru K.; Terasawa, Toshio, 2014, The Astrophysical Journal
The Evolution of High-temperature Plasma in Magnetar Magnetospheres and its Implications for Giant Flares

Y. Takamori, H.Okawa, M. Takamoto, Y Suwa, 2013, accepted in Publications of the Astronomical Society of Japan
An Alternative Numerical Method for the Stationary Pulsar Magnetosphere

M. Takamoto, 2013, The Astrophysical Journal
Evolution of Relativistic Plasmoid Chains in a Poynting-Dominated Plasma

I. Mochol & J.G. Kirk, 2013, The Astrophysical Journal
Propagation and stability of superluminal waves in pulsar winds

T. Amano & J.G. Kirk, 2013, The Astrophysical Journal
The Role of Superluminal Electromagnetic Waves in Pulsar Wind Termination Shocks

I. Mochol, PhD thesis, 2012
Nonlinear waves in Poynting-flux dominated outflows

Mochol, I. & Kirk, J.G. 2012, EPS Conference on Plasma Physics
Strong Electromagnetic Waves and Pulsar Termination Shocks

Arka, Ioanna & Kirk, John G. 2012, The Astrophysical Journal
Superluminal Waves in Pulsar Winds

I. Arka, PhD thesis, 2011
Non-linear waves in the laboratory and in astrophysics: Pair production in counter-propagating laser beams and strong waves in pulsar winds

Kirk, J.G. & Arka, I. 2011, Asian-Pacific Regional IAU Meeting
Of Winds and Waves

Kirk, J. G. 2010, Plasma Physics and Controlled Fusion
Waves in pulsar winds