Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photoionization effects in streamer discharges   In this paper we study the effects of photoionization processes on the
propagation of both negative and positive streamer discharges. We show that
negative fronts accelerate in the presence of photoionization events. The
appearance and propagation of positive streamers travelling with constant
velocity is explained as the result of the combined effects of photoionization
and electron diffusion. The photoionization range plays an important role for
the selection of the velocity of the streamer as we show in this work.

16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con