Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structure on Interplanetary Shock Fronts: Type II Radio Burst Source
  Regions   We present \emph{in situ} observations of the source regions of
interplanetary (IP) type II radio bursts, using data from the Wind spacecraft
during the period 1996-2002. We show the results of this survey as well as
in-depth analysis of several individual events. Each event analyzed in detail
is associated with an interplanetary coronal mass ejection (ICME) and an IP
shock driven by the ICME. Immediately prior to the arrival of each shock,
electron beams along the interplanetary magnetic field (IMF) and associated
Langmuir waves are detected, implying magnetic connection to a
quasiperpendicular shock front acceleration site. These observations are
analogous to those made in the terrestrial foreshock region, indicating that a
similar foreshock region exists on IP shock fronts. The analogy suggests that
the electron acceleration process is a fast Fermi process, and this suggestion
is borne out by loss cone features in the electron distribution functions. The
presence of a foreshock region requires nonplanar structure on the shock front.
Using Wind burst mode data, the foreshock electrons are analyzed to estimate
the dimensions of the curved region. We present the first measurement of the
lateral, shock-parallel scale size of IP foreshock regions. The presence of
these regions on IP shock fronts can explain the fine structure often seen in
the spectra of type II bursts.

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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: patt-sol
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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: comp-gas
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The categories of this paper are: econ