Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Suprathermal electrons at Saturn's bow shock   The leading explanation for the origin of galactic cosmic rays is particle
acceleration at the shocks surrounding young supernova remnants (SNRs),
although crucial aspects of the acceleration process are unclear. The similar
collisionless plasma shocks frequently encountered by spacecraft in the solar
wind are generally far weaker (lower Mach number) than these SNR shocks.
However, the Cassini spacecraft has shown that the shock standing in the solar
wind sunward of Saturn (Saturn's bow shock) can occasionally reach this
high-Mach number astrophysical regime. In this regime Cassini has provided the
first in situ evidence for electron acceleration under quasi-parallel upstream
magnetic conditions. Here we present the full picture of suprathermal electrons
at Saturn's bow shock revealed by Cassini. The downstream thermal electron
distribution is resolved in all data taken by the low-energy electron detector
(CAPS-ELS, <28 keV) during shock crossings, but the higher energy channels were
at (or close to) background. The high-energy electron detector (MIMI-LEMMS, >18
keV) measured a suprathermal electron signature at 31 of 508 crossings, where
typically only the lowest energy channels (<100 keV) were above background. We
show that these results are consistent with theory in which the "injection" of
thermal electrons into an acceleration process involves interaction with
whistler waves at the shock front, and becomes possible for all upstream
magnetic field orientations at high Mach numbers like those of the strong
shocks around young SNRs. A future dedicated study will analyze the rare
crossings with evidence for relativistic electrons (up to ~1 MeV).

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The categories of this paper are: patt-sol
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The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
2
The categories of this paper are: math
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The categories of this paper are: ao-sci
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The categories of this paper are: math-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: cs