153 research outputs found
Comoving acceleration of overdense electron-positron plasma by colliding ultra-intense laser pulses
Particle-in-cell (PIC) simulation results of sustained acceleration of
electron-positron (e+e-) plasmas by comoving electromagnetic (EM) pulses are
presented. When a thin slab of overdense e+e- plasma is irradiated with
linear-polarized ultra-intense short laser pulses from both sides, the pulses
are transmitted when the plasma is compressed to thinner than ~ 2 relativistic
skin depths. A fraction of the plasma is then captured and efficiently
accelerated by self-induced JxB forces. For 1 micron laser and 1021Wcm-2
intensity, the maximum energy exceeds GeV in a picosecond.Comment: 10 pages, 4 figure
Sustained Acceleration of Over-dense Plasmas by Colliding Laser Pulses
We review recent PIC simulation results which show that double-sided
irradiaton of a thin overdense plasma slab by ultra-intense laser pulses from
both sides can lead to sustained comoving acceleration of surface electrons to
energies much higher than the conventional ponderomotive limit. The
acceleration stops only when the electrons drift transversely out of the laser
beam. We show results of parameter studies based on this concept and discuss
future laser experiments that can be used to test these computer results.Comment: 9 pages 6 figures. AIP Conference Proceedings for 2005 Varenna Conf.
on Superstrong Fields in Plasmas (AIP, NY 2006
Soft gamma rays from black holes versus neutron stars
The recent launches of GRANAT and GRO provide unprecedented opportunities to study compact collapsed objects from their hard x ray and gamma ray emissions. The spectral range above 100 keV can now be explored with much higher sensitivity and time resolution than before. The soft gamma ray spectral data is reviewed of black holes and neutron stars, radiation, and particle energization mechanisms and potentially distinguishing gamma ray signatures. These may include soft x ray excesses versus deficiencies, thermal versus nonthermal processes, transient gamma ray bumps versus power law tails, lines, and periodicities. Some of the highest priority future observations are outlines which will shed much light on such systems
Plasma Radiation Model of Fast Radio Bursts from Magnetars
We propose a novel idea for the coherent intense millisecond radio emission
of cosmic fast radio bursts (FRBs), which have recently been identified with
flares from a magnetar. Motivated by the conventional paradigm of Type III
solar radio bursts, we will explore the emission of coherent plasma line
radiation at the electron plasma frequency and its harmonic as potential
candidates of the coherent FRB emissions associated with magnetar flares. We
discuss the emissions region parameters in relativistic strongly magnetized
plasmas consisting of electrons, positrons and protons. The goal is to make
observable predictions of this model to confront the multi-wavelength
observations of FRBs from magnetars. These results will impact both
observational radio astronomy and space-based astrophysicsComment: 13 pages 7 figure
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