Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear wave interactions as a model for naturally enhanced
  ion-acoustic lines in the ionosphere   Incoherent radar scatter from the ionosphere will, for equilibrium
conditions, show two symmetric ion-acoustic lines, one for each direction of
wave propagation. Many observation, from the EISCAT Svalbard Radar (ESR) for
instance, demonstrate that the symmetry of this ion line can be broken,
accompanied by an enhanced, nonthermal, level of fluctuations, i.e., Naturally
Enhanced Ion-Acoustic Lines (NEIALs). Several models have been proposed for
explaining these naturally enhanced lines. Here, we consider one of these,
suggesting that decay of electron beam excited Langmuir waves gives rise to
enhanced asymmetric ion lines in the ionosphere. We use a weak-turbulence
approximation, and identify crucial parameters for Langmuir decay processes to
be effective in generating the observed signals.

5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org