Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic field generation by charge exchange in a supernova remnant in
  the early universe   We present new generation mechanisms of magnetic fields in supernova remnant
shocks propagating to partially ionized plasmas in the early universe. Upstream
plasmas are dissipated at the collisionless shock, but hydrogen atoms are not
dissipated because they do not interact with electromagnetic fields. After the
hydrogen atoms are ionized in the shock downstream region, they become cold
proton beams that induce the electron return current. The injection of the beam
protons can be interpreted as an external force acting on the downstream proton
plasma. We show that the effective external force and the electron return
current can generate magnetic fields without any seed magnetic fields. The
magnetic field strength is estimated to be $B\sim 10^{-14}-10^{-11}~{\rm G}$,
where the characteristic lengthscale is the mean free path of charge exchange,
$\sim 10^{15}~{\rm cm}$. Since protons are marginally magnetized by the
generated magnetic field in the downstream region, the magnetic field could be
amplified to larger values and stretched to larger scales by turbulent dynamo
and expansion.

10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th