Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Subcritical growth of electron phase-space holes in planetary radiation
  belts   The discovery of long-lived electrostatic coherent structures with
large-amplitude electric fields ($1 \leq E \leq 500 $ mV/m) by the Van Allen
Probes has revealed alternative routes through which planetary radiation belts'
acceleration can take place. Following previous reports showing that small
phase-space holes, with $q\phi /T^c_e\simeq 10^{-2}-10^{-3}$, could result from
electron interaction with large-amplitude whistlers, we demonstrate one
possible mechanism through which holes can grow nonlinearly (i.e. $\gamma
\propto \sqrt{\phi}$) and subcritically as a result of momentum exchange
between hot and cold electron populations. Our results provide an explanation
for the common occurrence and fast growth of large-amplitude electron
phase-space holes in the Earth's radiation belts.

10
The categories of this paper are: q-bio
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The categories of this paper are: eess
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
2
The categories of this paper are: math
1
The categories of this paper are: cs
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
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The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph