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Plasma Interactions in the Crab Nebula

Published online by Cambridge University Press:  07 February 2017

F. D. Kahn
F. D. Kahn*
Affiliation:
Astronomy Department, University of Manchester, Manchester, U.K.

Abstract

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Alfvén waves can be carried by the thermal plasma in the Crab Nebula. Each such wave perturbs the relativistic plasma present, in particular it strongly affects those particles which are in resonance with it. For a wave travelling parallel to the magnetic field the resonances are quite simple, but a wave travelling obliquely can give rise to multiple resonances, and can therefore couple together particles with quite different energies.

It is shown that the interaction with the relativistic plasma leads to an amplification of the Alfvén waves when the mean velocity of relativistic plasma relative to the thermal plasma exceeds the Alfvén speed. The rise time for the instability is quite short, and the waves, once excited, are highly effective in redistributing the directions of motion of the relativistic particles. The relativistic plasma therefore cannot stream freely through the thermal plasma. On the other hand the disturbances will never quite die out in the Crab Nebula as long as the Crab pulsar keeps injecting fresh plasma, and thus keeps producing new inhomogeneities in the relativistic plasma density.

Type
Session 5
Information
Symposium - International Astronomical Union , Volume 46: The Crab Nebula , 1971 , pp. 281 - 291
Copyright
Copyright © Reidel 1971 

References

Details of the physics of the Crab Nebula are given in several other papers contributed to this symposium.Google Scholar
The theory of Alfvén waves and of plasma waves has been discussed by many authors, including Google Scholar
Clemmow, P. C. and Dougherty, J. P., Electrodynamics of Particles and Plasmas , Addison Wesley, 1969.Google Scholar
The importance of the interaction of relativistic plasmas and Alfvén waves in the interstellar plasma has been emphasied by a number of authors. The effect is essentially the same as that in the Crab Nebula. References are Google Scholar
Kulsrud, R. M. and Pearce, W. P.: 1969, Astrophys. J. 156, 445.Google Scholar
Skilling, J.: 1970, Monthly Notices Roy. Astron. Soc. 147, 1.Google Scholar
Wentzel, D. G.: 1969, Astrophys. J. 156, 303.Google Scholar
Skilling in particular gives an interesting discussion of the associated physical effects.Google Scholar