Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spark Model for Pulsar Radiation Modulation Patterns   A non-stationary polar gap model first proposed by Ruderman & Sutherland
(1975) is modified and applied to spark-associated pulsar emission at radio
wave-lengths. It is argued that under physical and geometrical conditions
prevailing above pulsar polar cap, highly non-stationary spark discharges do
not occur at random positions. Instead, sparks should tend to operate in well
determined preferred regions. At any instant the polar cap is populated as
densely as possible with a number of two-dimensional sparks with a
characteristic dimension as well as a typical distance between adjacent sparks
being about the polar gap height. Our model differs, however, markedly from its
original 'hollow cone' version. The key feature is the quasi-central spark
driven by pair production process and anchored to the local pole of a
sunspot-like surface magnetic field. This fixed spark prevents the motion of
other sparks towards the pole, restricting it to slow circumferential drift
across the planes of field lines converging at the local pole. We argue that
the polar spark constitutes the core pulsar emission, and that the annular
rings of drifting sparks contribute to conal components of the pulsar beam. We
found that the number of nested cones in the beam of typical pulsar should not
excced three; a number also found by Mitra & Deshpande (1999) using a
completely different analysis.

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The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: funct-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: cond-mat
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The categories of this paper are: physics
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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom