Speaker
Dr
Daniel Kagan
(Tel Aviv University)
Description
We investigate the acceleration of particles beyond the synchrotron burnoff limit of
the background magnetic field in relativistic magnetic reconnection by analysing the
effects of radiative cooling on test particles incident on a large reconnection
region in a 2D particle-in-cell simulation. We find that the trajectories of the
particles are not significantly affected by cooling while they are in the
reconnection region, but that their energies are significantly decreased if the
uncooled final energy is significantly higher than the burnoff limit corresponding to
the average magnetic field experienced by the particle in its trajectory in the
reconnection region. We present a semi-analytical model to calculate this average
magnetic field experienced by a particle as a function of energy in our simulations
and compare it to previous analytical work based on Speiser orbit calculations,
finding reasonable agreement between the two approaches. We then use our model to
calculate the predicted cooled spectrum corresponding to an uncooled power law, and
find that for hard power laws typically produced in reconnection simulations, cooling
produces a break in the power law at high energy but the change in index of the power
law is slight. Thus, our simulation and our model predict that the synchrotron
burnoff limit does not present a signficant limitation to the energy reached by
particles accelerated in magnetic reconnection.
Primary author
Dr
Daniel Kagan
(Tel Aviv University)
Co-authors
Prof.
Ehud Nakar
(Tel Aviv University)
Prof.
Tsvi Piran
(Hebrew University of Jerusalem)
