Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Simulations of galactic dynamos   We review our current understanding of galactic dynamo theory, paying
particular attention to numerical simulations both of the mean-field equations
and the original three-dimensional equations relevant to describing the
magnetic field evolution for a turbulent flow. We emphasize the theoretical
difficulties in explaining non-axisymmetric magnetic fields in galaxies and
discuss the observational basis for such results in terms of rotation measure
analysis. Next, we discuss nonlinear theory, the role of magnetic helicity
conservation and magnetic helicity fluxes. This leads to the possibility that
galactic magnetic fields may be bi-helical, with opposite signs of helicity and
large and small length scales. We discuss their observational signatures and
close by discussing the possibilities of explaining the origin of primordial
magnetic fields.

27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs