Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Second order Fermi reacceleration mechanisms and large scale synchrotron
  radio emission in intra-cluster bridges   Radio observations at low frequencies with the Low Frequency Array (LOFAR)
start discovering gigantic radio bridges connecting pairs of massive galaxy
clusters. These observations probe unexplored mechanisms of in situ particle
acceleration that operate on volumes of several Mpc$^3$. Numerical simulations
suggest that such bridges are dynamically complex and that weak shocks and
super-Alfv\'{e}nic turbulence can be driven across the entire volume of these
regions. In this Letter we explore, for the first time, the role of second
order Fermi mechanisms for the reacceleration of relativistic electrons
interacting with turbulence in these peculiar regions. We assume the turbulent
energy flux measured in simulations and adopt a scenario in which relativistic
particles scatter with magnetic field lines diffusing in super-Alfv\'enic
turbulence and magnetic fields are amplified by the same turbulence. We show
that steep spectrum and volume filling synchrotron emission can be generated in
the entire intra-cluster bridge region thus providing a natural explanation for
radio bridges. Consequently, radio observations have the potential to probe the
dissipation of energy on scales larger than galaxy clusters and second order
Fermi mechanisms operating in physical regimes that are still poorly explored.
This has a potential impact on several branches of astrophysics and cosmology.

27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an