174 research outputs found
Kinetic simulations of relativistic magnetic reconnection with synchrotron and inverse Compton cooling
First results are presented from kinetic numerical simulations of
relativistic collisionless magnetic reconnection in pair plasma that include
radiation reaction from both synchrotron and inverse Compton (IC) processes,
motivated by non-thermal high-energy astrophysical sources, including in
particular blazars. These simulations are initiated from a configuration known
as 'ABC fields' that evolves due to coalescence instability and generates thin
current layers in its linear phase. Global radiative efficiencies, instability
growth rates, time-dependent radiation spectra, lightcurves, variability
statistics and the structure of current layers are investigated for a broad
range of initial parameters. We find that the IC radiative signatures are
generally similar to the synchrotron signatures. The luminosity ratio of IC to
synchrotron spectral components, the Compton dominance, can be modified by more
than one order of magnitude with respect to its nominal value. For very short
cooling lengths, we find evidence for modification of the temperature profile
across the current layers, no systematic compression of plasma density, and
very consistent profiles of E.B. We decompose the profiles of E.B with the use
of the Vlasov momentum equation, demonstrating a contribution from radiation
reaction at the thickness scale consistent with the temperature profile.Comment: 18 pages, 6 figures, accepted for publication in the Journal of
Plasma Physics, special collection "Plasma physics under extreme conditions:
from high-energy-density experiments to astrophysics", Eds. F. Fiuza, R. D.
Blandford & S. Glenze
Black hole magnetosphere with small scale flux tubes--II. Stability and dynamics
In some Seyfert Galaxies, the hard X-rays that produce fluorescent emission
lines are thought to be generated in a hot corona that is compact and located
at only a few gravitational radii above the supermassive black hole. We
consider the possibility that this X-ray source may be powered by small scale
magnetic flux tubes attached to the accretion disk near the black hole. We use
three dimensional, time dependent force-free simulations in a simplified
setting to study the dynamics of such flux tubes as they get continuously
twisted by the central compact star/black hole. We find that, the dynamical
evolution of the flux tubes connecting the central compact object and the
accretion disk is strongly influenced by the confinement of the surrounding
field. Although differential rotation between the central object and the disk
tends to inflate the flux tubes, strong confinement from surrounding field
quenches the formation of a jet-like outflow, as the inflated flux tube becomes
kink unstable and dissipates most of the extracted rotational energy relatively
close to the central object. Such a process may be able to heat up the plasma
and produce strong X-ray emission. We estimate the energy dissipation rate and
discuss its astrophysical implications.Comment: 16 pages, 17 figures. Accepted for publication in MNRA
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