Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Kinetic energy flux versus Poynting flux in MHD winds and jets: the
  intermediate regime   We show that the formal asymptotic limit for all rotating polytropic
axisymmetric perfect MHD flows is a kinetic energy dominated wind which
collimates to paraboloids around the symmetry axis. We reach this result by
showing that another, a priori possible, solution with finite Poynting flux can
be excluded on the following physical grounds: (1) the wind velocity does not
exceed the fast mode speed everywhere and (2) the circumpolar current increases
with distance from the source.We show that asymptotic hoop stress collimation
is mathematically robust and we give strong arguments why recent
anti-collimation claims are not correct. However, in practice, due to the very
slow logarithmic decline of the circumpolar current with increasing distance
from the source, there is a broad intermediate regime with significant Poynting
flux. This intermediate regime, rather than the mathematically exact asymptotic
regime, may well apply along the finite length of the jet. We briefly discuss
peculiarities that would be associated with Poynting jets in the intermediate
regime. Force-free initial conditions in the near field are most likely to
produce such jets, in which most of the energy flux is electromagnetic.

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The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an