On the electric field screening by electron–positron pairs in a pulsar magnetosphere |
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| Authors: | S Shibata J Miyazaki & F Takahara |
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| Institution: | Department of Physics, Yamagata University, 1-4-12 Kojirakawa, Yamagata 990, Japan,;Department of Physics, Tokyo Metropolitan University, Minamiohsawa 1-1, Hachioji, Tokyo 192-03, Japan |
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| Abstract: | We present a steady one-dimensional model for a pulsar polar cap accelerator, where the field-aligned electric field and flow are solved self-consistently with a given current density. It is assumed that no particles return to the star. It is known that the space-charge-limited flow is accelerated to energies high enough to create electron–positron pairs if the assumed current density is high enough. We find that when pairs are created in such a space-charge-limited flow, the accelerating electric field is screened out within a short distance after pair creation, if the pair particle flux is larger than a critical value. We also find that a space charge density wave is excited in the screening region.
We find that a pair flux larger than the critical value M c=103–105 must be reached in a layer with thickness equal to the braking distance for the decelerating component. Therefore, the required multiplicity – the number of pairs created by one primary particle – is too large to be realized in the actual pulsar magnetosphere. We suggest that in order to obtain a localized potential drop along the polar cap magnetic flux, one needs to take into account additional effects such as wave–particle interaction or quasi-periodic pair creation. |
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| Keywords: | magnetic fields plasmas pulsars: general gamma-rays: theory |
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