Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Current-driven filamentation upstream of magnetized relativistic
  collisionless shocks   The physics of instabilities in the precursor of relativistic collisionless
shocks is of broad importance in high energy astrophysics, because these
instabilities build up the shock, control the particle acceleration process and
generate the magnetic fields in which the accelerated particles radiate. Two
crucial parameters control the micro-physics of these shocks: the magnetization
of the ambient medium and the Lorentz factor of the shock front; as of today,
much of this parameter space remains to be explored. In the present paper, we
report on a new instability upstream of electron-positron relativistic shocks
and we argue that this instability shapes the micro-physics at moderate
magnetization levels and/or large Lorentz factors. This instability is seeded
by the electric current carried by the accelerated particles in the shock
precursor as they gyrate around the background magnetic field. The compensation
current induced in the background plasma leads to an unstable configuration,
with the appearance of charge neutral filaments carrying a current of the same
polarity, oriented along the perpendicular current. This ``current-driven
filamentation'' instability grows faster than any other instability studied so
far upstream of relativistic shocks, with a growth rate comparable to the
plasma frequency. Furthermore, the compensation of the current is associated
with a slow-down of the ambient plasma as it penetrates the shock precursor (as
viewed in the shock rest frame). This slow-down of the plasma implies that the
``current driven filamentation'' instability can grow for any value of the
shock Lorentz factor, provided the magnetization \sigma <~ 10^{-2}. We argue
that this instability explains the results of recent particle-in-cell
simulations in the mildly magnetized regime.

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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
24
The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph
25
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: adap-org
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The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin