Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Study of time evolution of the bend-over energy in the energetic
  particle spectrum at a parallel shock   Shock acceleration is considered one of the most important mechanisms for the
acceleration of astrophysical energetic particles. In this work, we calculate
the trajectories of a large number of test charged particles accurately in a
parallel shock with magnetic turbulence. We investigate the time evolution of
the accelerated-particle energy spectrum in the downstream of the shock in
order to understand the acceleration mechanism of energetic particles. From
simulation results we obtain power-law energy spectra with a bend-over energy,
$E_0$, increasing with time. With the particle mean acceleration time and mean
momentum change during each cycle of the shock crossing from diffusive shock
acceleration model (following Drury), a time-dependent differential equation
for the maximum energy, $E_{acc}$, of particles accelerated at the shock, can
be approximately obtained. We assume the theoretical bend-over energy as
$E_{acc}$. It is found that the bend-over energy from simulations agrees well
with the theoretical bend-over energy using the non-linear diffusion theory,
NLGCE-F, in contrast to that using the classic quasi-linear theory (QLT).

5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th