期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 408, 期 4, 页码 2092-2114出版社
WILEY-BLACKWELL
DOI: 10.1111/j.1365-2966.2010.17286.x
关键词
acceleration of particles; plasmas; stars: magnetic field; stars: neutron; pulsars: general
资金
- NSF [AST-0507813]
- NASA [NNG06GJI08G, NNX09AU05G]
- DOE [DE-FC02-06ER41453]
- NASA [NNX09AU05G, 107621] Funding Source: Federal RePORTER
I argue that the problem of electromagnetically driven electron-positron cascades in magnetospheres of neutron stars must be addressed starting from first principles. I describe a general numerical algorithm for doing self-consistent kinetic simulations of electron-positron cascades - wherein particle acceleration, pair creation and screening of the electric field are calculated simultaneously - and apply it to model the Ruderman & Sutherland cascade in one dimension. I find that pair creation is quite regular and quasi-periodic. In each cycle a blob of ultra-relativistic electron-positron plasma is generated; it propagates into the magnetosphere leaving a tail of less relativistic plasma behind, and the next discharge occurs when this mildly relativistic plasma leaves the polar cap. A short burst of pair formation is followed by a longer quiet phase when accelerating electric field is screened and no pairs are produced. Some of freshly injected electron-positrons pairs get trapped in plasma oscillations creating a population of low-energy particles. The cascade easily adjusts to the current density required by the pulsar magnetosphere by reversing some of the low-energy particles. Each discharge generates a strong coherent superluminal electrostatic wave, which may be relevant for the problem of pulsar radioemission.
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