Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the background-gyroresonant character of the Bell instability   We show that the Bell instability, which is widely considered potentially
important for cosmic-ray acceleration, is the low-frequency limit of a
gyroresonant interaction between the protons of the interstellar medium and
shear-Alfv\'en waves. At large cosmic-ray current densities, its growth rate is
therefore limited by the proton gyrofrequency, and two modes emerge from the
cold-beam dispersion relation. A third mode driven by electron gyroresonance is
only weakly unstable at low current densities. We discuss implications for
magnetic-field amplification and its saturation in the vicinity of supernova
remnants.

36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
2
The categories of this paper are: math
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom