Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Need For High Resolution In Studies Of The 3-D Magnetic Field
  Structure Of AGN Jets   We are using "broadband" (4.6 to 43 GHz) multi-frequency VLBA polarization
observations of compact AGN to investigate the 3-D structure of their jet
magnetic (B) fields. Observing at several frequencies, separated by short and
long intervals, enables reliable determination of the distribution of Faraday
Rotation, and thereby the intrinsic B field structure. Transverse Rotation
Measure (RM) gradients were detected in the jets of 0954+658 and 1418+546,
providing evidence for the presence of a helical B field surrounding the jet.
The RM in the core regions of 2200+420 (BL Lac), 0954+658 and 1418+546 display
different signs in different frequency-intervals (on different spatial scales);
we suggest an explanation for this in terms of modest bends in a helical B
field surrounding their jets. In future, polarization observations with a
combination of VSOP-2 at 8, 22 and 43 GHz and ground arrays at frequencies with
corresponding resolution will help map out the distributions of Faraday
rotation, spectral index and the 3-D B field structure both across the jet and
closer to the central engine, providing strong constraints for any jet B field
models.

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The categories of this paper are: econ
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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The categories of this paper are: cs
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: physics
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The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: hep-lat
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The categories of this paper are: chao-dyn