Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The influence of electron density gradient direction on gradient-drift
  instabilities in the E-layer of the ionosphere   We show that the dispersion relation for gradient-drift and Farley-Buneman
instabilities within the approximation of the two-fluid MHD should contain the
terms which are traditionally supposed to be small. These terms are caused by
taking into account divergence of particles velocity and electron density
gradient along the magnetic field direction. It is shown that at heights below
115km the solution of the dispersion relation transforms into standard one,
except the situations, when the electron density gradient is parallel to
magnetic field or wave-vector. In these cases the traditionally neglected
summands to the growth rate of the irregularities becomes significant. The
additional terms depend on relative directions of electron density gradient,
magnetic field and mean velocities. This leads to the different instability
growth conditions at equatorial and high-latitude regions of the ionosphere.
The obtained results do not contradict with the experimental data.

14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph