Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radial profile of the polytropic index of solar wind plasma in the
  heliosphere   We combine different measurements of the polytropic index of the proton
plasma in the heliosphere: i) near-adiabatic index in the inner heliosphere
~1AU, ii) subadiabatic indices in the outer heliosphere ~20-40AU, and iii)
near-zero indices in the inner heliosheath. These observations are unified by a
single theoretical model of the polytropic index throughout its radial extent
in the heliosphere; the corresponding fitting reveals the decreasing trend of
the polytropic index with increasing heliocentric distance R. We anticipate
that with increasing R, (i) the Debye length and mean-free-path decreases; (ii)
the Landau damping is less effective, transferring thus less wave energy to
particles; and (iii) the collisionality degree increases, indicating that the
proton plasma in the inner heliosheath might be collisionless.

4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg