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Title: Simulation of high-energy proton production by fast magnetosonic shock waves in pinched plasma discharges

Abstract

High-energy particles of a few hundred keV for electrons and up to MeV for ions were observed in a plasma focus device. Haruki et al. [Phys. Plasmas 13, 082106-1 (2006)] studied the mechanism of high-energy particle production in pinched plasma discharges by use of a 3D relativistic and fully electromagnetic particle-in-cell code. It was found that the pinched current is unstable against a sausage instability, and then becomes unstable against a kink instability. As a result high-energy electrons were observed, but protons with MeV energies were not observed. In this paper the same pinch dynamics as Haruki and co-workers is investigated, focusing on the shock formation and the shock acceleration during the pinched current. It is found that a fast magnetosonic shock wave is produced during the pinching phase which, after the maximum pinch occurs, is strongly enhanced and propagates outwards. Some protons trapped in the electrostatic potential produced near the shock front can be accelerated to a few MeV by the surfatron acceleration mechanism. It is also found that the protons accelerated along the pinched axis have a ring-shaped angular distribution that is observed from numerous experiments.

Authors:
; ; ; ;  [1]
  1. Department of Electric and Electronic Systems, Faculty of Engineering, University of Toyama, 3190 Gofuku, Toyama, Toyama 930-8555 (Japan)
Publication Date:
OSTI Identifier:
20976602
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 3; Other Information: DOI: 10.1063/1.2716673; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATION; ANGULAR DISTRIBUTION; ELECTRONS; IONS; KEV RANGE; KINK INSTABILITY; MEV RANGE; PINCH EFFECT; PLASMA FOCUS; PLASMA FOCUS DEVICES; PLASMA SIMULATION; PROTONS; RELATIVISTIC PLASMA; RELATIVISTIC RANGE; SAUSAGE INSTABILITY; SHOCK WAVES

Citation Formats

Mizuguchi, Yusuke, Sakai, Jun-Ichi, Yousefi, Hamid Reza, Haruki, Takayuki, and Masugata, Katsumi. Simulation of high-energy proton production by fast magnetosonic shock waves in pinched plasma discharges. United States: N. p., 2007. Web. doi:10.1063/1.2716673.
Mizuguchi, Yusuke, Sakai, Jun-Ichi, Yousefi, Hamid Reza, Haruki, Takayuki, & Masugata, Katsumi. Simulation of high-energy proton production by fast magnetosonic shock waves in pinched plasma discharges. United States. doi:10.1063/1.2716673.
Mizuguchi, Yusuke, Sakai, Jun-Ichi, Yousefi, Hamid Reza, Haruki, Takayuki, and Masugata, Katsumi. Thu . "Simulation of high-energy proton production by fast magnetosonic shock waves in pinched plasma discharges". United States. doi:10.1063/1.2716673.
@article{osti_20976602,
title = {Simulation of high-energy proton production by fast magnetosonic shock waves in pinched plasma discharges},
author = {Mizuguchi, Yusuke and Sakai, Jun-Ichi and Yousefi, Hamid Reza and Haruki, Takayuki and Masugata, Katsumi},
abstractNote = {High-energy particles of a few hundred keV for electrons and up to MeV for ions were observed in a plasma focus device. Haruki et al. [Phys. Plasmas 13, 082106-1 (2006)] studied the mechanism of high-energy particle production in pinched plasma discharges by use of a 3D relativistic and fully electromagnetic particle-in-cell code. It was found that the pinched current is unstable against a sausage instability, and then becomes unstable against a kink instability. As a result high-energy electrons were observed, but protons with MeV energies were not observed. In this paper the same pinch dynamics as Haruki and co-workers is investigated, focusing on the shock formation and the shock acceleration during the pinched current. It is found that a fast magnetosonic shock wave is produced during the pinching phase which, after the maximum pinch occurs, is strongly enhanced and propagates outwards. Some protons trapped in the electrostatic potential produced near the shock front can be accelerated to a few MeV by the surfatron acceleration mechanism. It is also found that the protons accelerated along the pinched axis have a ring-shaped angular distribution that is observed from numerous experiments.},
doi = {10.1063/1.2716673},
journal = {Physics of Plasmas},
number = 3,
volume = 14,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • In an experimental plasma, high-energy particles were observed by using a plasma focus device, to obtain energies of a few hundred keV for electrons, up to MeV for ions. In order to study the mechanism of high-energy particle production in pinched plasma discharges, a numerical simulation was introduced. By use of a three-dimensional relativistic and fully electromagnetic particle-in-cell code, the dynamics of a Z-pinch plasma, thought to be unstable against sausage and kink instabilities, are investigated. In this work, the development of sausage and kink instabilities and subsequent high-energy particle production are shown. In the model used here, cylindrically distributedmore » electrons and ions are driven by an external electric field. The driven particles spontaneously produce a current, which begins to pinch by the Lorentz force. Initially the pinched current is unstable against a sausage instability, and then becomes unstable against a kink instability. As a result high-energy particles are observed.« less
  • In collisionless magnetosonic shock waves, ions are commonly thought to be decelerated by dc electrostatic cross-shock electric field along the shock normal n. In a frame where ions are normally incident to the shock the change in the potential energy (qphi/sup N/) in the quasi-perpendicular geommetry is of the order of the change of the energy of normal ion flow: (qphi/sup N/)roughly-equal(1/2m/sub i/(V/sub i//sup N/xn)/sup 2/), which is approximately 200-500 eV at the earth's bow shock. We show that the electron energy gain, typically 1/10 this number, is consistent with such a large potential jump in this geometry. Key factsmore » are the different paths taken by electrons an ions through the shock wave and the frame dependence of the potential jump in the geometry. In the normal incidence frame, electrons lose energy by doing work against the solar wind motional electric field E/sub M//sup N/, which partially offsets the energy gain from the cross-shock electrostatic potential energy (ephi/sub asterisk//sup N/). In the de Hoffman-Teller frame the motional electric field vanishes; the elctrons gain the full electrostatic potential energy jump e(phi/sub asterisk//sup H//sup T/) of that frame, which is not, however, equal to the electrostatic potential energy jump e(phi/sub asterisk//sup N/) of that frame, which is not, however, equal to the electrostatic potential energy jump e(phi/sub asterisk//sup N/) in the normal incidence frame.« less
  • Observational data and theoretical models suggest that the wave spectrum in the solar wind and corona may contain a fast magnetosonic mode component. This paper presents two-dimensional hybrid simulations of the energy cascade among the fast waves in the vicinity of the proton inertial scale. The initial spectrum consists of modes propagating in the positive direction, defined by the mean magnetic field, and is allowed to evolve freely in time. The plasma beta is set to low values typical of the solar corona. The cascade proceeds from lower to higher wavenumbers and mostly in the direction across the magnetic field.more » The highly oblique fast waves are strongly dissipated on the protons. The resulting proton heating is preferentially perpendicular to the magnetic field. If the wave intensity is constrained by the observed density spectra in the corona, the heating is fast enough to generate the solar wind.« less
  • A model is considered of the conversion of running fast magnetosonic waves into Alfven waves in a longitudinally inhomogeneous gyrotropic plasma in a magnetic field with open field lines. The set of equations for the amplitudes of the interacting modes is obtained and investigated in the Wentzel-Kramers-Brillouin approximation. In the synchronization region, where the wave vectors of the two modes approach one another, most of the energy of fast magnetosonic waves is converted into the Alfven wave energy. The phases of the waves are matched in such a way that the phase difference is most favorable for wave conversion. Themore » fact that the conversion is resonant in nature may help to explain the onset of quasi-monochromatic signals in the Earth's magnetosphere and in the magnetospheres of the giant planets.« less