Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A class of exact MHD models for astrophysical jets   This paper examines a new class of exact and self-consistent MHD solutions
which describe steady and axisymmetric hydromagnetic outflows from the
atmosphere of a magnetized and rotating central object with possibly an
orbiting accretion disk. The plasma is driven against gravity by a thermal
pressure gradient, as well as by magnetic rotator and radiative forces. At the
Alfvenic and fast critical points the appropriate criticality conditions are
applied. The outflow starts almost radially but after the Alfven transition and
before the fast critical surface is encountered the magnetic pinching force
bends the poloidal streamlines into a cylindrical jet-type shape. The terminal
speed, Alfven number, cross-sectional area of the jet, as well as its final
pressure and density obtain uniform values at large distances from the source.
The goal of the study is to give an analytical discussion of the
two-dimensional interplay of the thermal pressure gradient, gravitational,
Lorentz and inertial forces in accelerating and collimating an MHD flow. A
parametric study of the model is also given, as well as a brief sketch of its
applicability to a self-consistent modelling of collimated outflows from
various astrophysical objects. {The analysed model succeeds to give for the
first time an exact and self-consistent MHD solution for jet-type outflows
extending from the stellar surface to infinity where it can be superfast, in
agreement with the MHD causality principle.

25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph