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Particle acceleration in laser-driven magnetic reconnection
Particle acceleration induced by magnetic reconnection is thought to be a promising candidate for producing the nonthermal emissions associated with explosive phenomena such as solar flares, pulsar wind nebulae, and jets from active galactic nuclei. Laboratory experiments can play an important role...
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Published in: | Physics of plasmas 2017-04, Vol.24 (4) |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Particle
acceleration induced by magnetic reconnection is thought to be a promising
candidate for producing the nonthermal emissions associated with explosive phenomena such
as solar flares, pulsar wind nebulae, and jets from active galactic nuclei. Laboratory
experiments can play an important role in the study of the detailed microphysics of
magnetic
reconnection and the dominant particle acceleration mechanisms. We have used two- and
three-dimensional particle-in-cell
simulations to study particle acceleration in high Lundquist number
reconnection
regimes associated with laser-driven plasma experiments. For current experimental
conditions, we show that nonthermal electrons can be accelerated to energies more than an order
of magnitude larger than the initial thermal energy. The nonthermal electrons gain their energy
mainly from the reconnection
electric field
near the X points, and particle injection into the
reconnection
layer and escape from the finite system establish a distribution of energies that
resembles a power-law spectrum. Energetic electrons can also become trapped inside the plasmoids that
form in the current layer and gain additional energy from the electric field arising from the
motion of the plasmoid. We compare simulations for finite and infinite periodic systems to
demonstrate the importance of particle escape on the shape of the spectrum. Based on our
findings, we provide an analytical estimate of the maximum electron energy and threshold
condition for observing suprathermal electron acceleration in terms of experimentally tunable
parameters. We also discuss experimental signatures, including the angular distribution of
the accelerated particles, and construct synthetic detector spectra. These results open
the way for novel experimental studies of particle acceleration induced by reconnection. |
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ISSN: | 1070-664X 1089-7674 |
DOI: | 10.1063/1.4978627 |