Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New mechanism of generation of large-scale magnetic fields in merging
  protogalactic and protostellar clouds   A new mechanism of generation of large-scale magnetic fields in colliding
protogalactic clouds and merging protostellar clouds is discussed. Interaction
of the colliding clouds produces large-scale shear motions which are
superimposed on small-scale turbulence. Generation of the large-scale magnetic
field is due to a ''shear-current" effect (or "vorticity-current" effect), and
the mean vorticity is caused by the large-scale shear motions of colliding
clouds. This effect causes the generation of the mean magnetic field even in a
nonrotating and nonhelical homogeneous turbulence. There is no quenching of the
nonlinear shear-current effect contrary to the quenching of the nonlinear alpha
effect, the nonlinear turbulent magnetic diffusion, etc. During the nonlinear
growth of the mean magnetic field, the shear-current effect only changes its
sign at some value of the mean magnetic field which determines the level of the
saturated mean magnetic field. Numerical study shows that the saturated level
of the mean magnetic field is of the order of the equipartition field
determined by the turbulent kinetic energy. The estimated large-scale magnetic
field for merging protogalactic clouds is about several microgauss, and for
merging protostellar clouds is of the order of several tenth of microgauss.

27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con