2,716 research outputs found
Particle Acceleration by Magnetic Reconnection
Observational data require a rich variety of mechanisms to accelerate fast
particles in astrophysical environments operating under different conditions.
The mechanisms discussed in the literature include varying magnetic fields in
compact sources, stochastic processes in turbulent environments, and
acceleration behind shocks. An alternative, much less explored mechanism
involves particle acceleration within magnetic reconnection sites. In this
chapter we discuss this mechanism and show that particles can be efficiently
accelerated by reconnection through a first order Fermi process within large
scale current sheets (specially when in the presence of local turbulence which
speeds up the reconnection and make the acceleration region thicker) and also
through a second order Fermi process in pure MHD turbulent environments.Comment: 24 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1103.2984, arXiv:1202.5256, arXiv:1008.1981 by other author
The role of pressure anisotropy in the turbulent intracluster medium
In low-density plasma environments, such as the intracluster medium (ICM),
the Larmour frequency is much larger than the ion-ion collision frequency. In
such a case, the thermal pressure becomes anisotropic with respect to the
magnetic field orientation and the evolution of the turbulent gas is more
correctly described by a kinetic approach. A possible description of these
collisionless scenarios is given by the so-called kinetic magnetohydrodynamic
(KMHD) formalism, in which particles freely stream along the field lines, while
moving with the field lines in the perpendicular direction. In this way a
fluid-like behavior in the perpendicular plane is restored. In this work, we
study fast growing magnetic fluctuations in the smallest scales which operate
in the collisionless plasma that fills the ICM. In particular, we focus on the
impact of a particular evolution of the pressure anisotropy and its
implications for the turbulent dynamics of observables under the conditions
prevailing in the ICM. We present results from numerical simulations and
compare the results which those obtained using an MHD formalism.Comment: 7 pages, 14 figures, Journal of Physics: Conference Serie
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