Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exact spirally symmetric galactic dynamos   This paper extends the results of an earlier paper on scale invariant
galactic spiral magnetic modes to time dependent, scale invariant, spirals. The
examples given are all exact in that they may be described in terms of
hypergeometric functions. We restrict the discussion to an infinitely
conducting medium in order to avoid earlier approximation, which limited the
solutions to cones lying within about twenty degrees to the plane. The magnetic
disc spirals, `X type" poloidal fields, and the recent discovery of rotation
measure screens in edge-on galactic halos were all recovered in such solutions.

27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph