Modelling the Evolution of Pulsar Wind Nebulae
Michael Vorster
(S. Ferreira, H. Moraal)
Centre for Space Research, North-West University, Potchefstroom, South Africa
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
Introduction
Supernova explosion
Massive star
●
●
Larger than 8
solar masses
Leads to
formation of a
shock wave
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
Supernova remnant
●
Sweeps up
and
accelerates
interstellar
matter radiation
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Introduction
●
Reverse shock
●
Initially propagates outward
●
Pressure difference develops between forward shock and
interior of remnant
●
Reverse shock propagates inward
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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Introduction
●
Collapsed core of progenitor star
●
Extremely large magnetic field
●
Pulsed emission
●
Relativistic magnetised wind
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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Introduction
Pressure of wind
equal to ambient
pressure
Particle
acceleration,
turbulence
(Aharonian & Bogovalov, 2002)
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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Introduction
Synchrotron
radiation,
inverse
Compton
scattering
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
(Aharonian & Bogovalov, 2002)
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Introduction
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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Introduction
Composite remnants
●
100-1000 more energy in SNR
●
PWN does not influence SNR
●
Reverse shock interacts with
PWN
●
Compresses PWN
(Gaensler & Slane, 2006)
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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Introduction
Composite remnants
●
Focus of talk: modelling the
evolution of the SNR-PWN system
(Gaensler & Slane, 2006)
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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Introduction
Motivation
●
Cosmic rays
●
Unidentified TeV sources
●
Relativistic shock acceleration
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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SNR-PWN models
●
Based on fluid dynamics
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Hydrodynamic models: Euler equations
●
Magnetohydrodynamic models
●
Equations are solved numerically
Current models are generally computationally intensive
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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SNR-PWN models
Hydrodynamic models
Advantage
Long-term evolution (kiloyears)
●
Disadvantage
●
No magnetic field
(Van der Swaluw et al., 2004)
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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SNR-PWN models
Magnetohydrodynamic models
Advantage
●
(Porth et al., 2013)
Simulate small scale structures
that are caused by magnetic
fields
(Del Zanna et al., 2006)
Disadvantage
●
Evolution of a few hundred years
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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SNR-PWN models
Kinematic models
●
Hydrodynamic model with a magnetic field
●
Effect of fluid on magnetic field taken into account
●
Reverse process neglected
●
Applicable when plasma beta is large (e.g., PWNe)
●
●
Advantage
●
Long term evolution of fluid as well as magnetic field
Disadvantage
●
Cannot resolve small scale structures
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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SNR-PWN models
(Vorster et al., 2013)
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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SNR-PWN models
Observations
(Aharonian et al., 2006)
(Vorster et al., 2013)
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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Summary
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Fluid models have been successful in simulating numerous aspects
of SNR-PWN evolution
●
However, all models have limitations
●
Limitations generally related to computational limitations
●
●
Ultimate goal: develop time-dependent, three dimensional
relativistic MHD model to simulate long term evolution
Becomes increasingly possible with advances in high performance
computing.
Centre for High Performance Computing meeting, Cape Town, 4-6 December (2013)
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