McClements, K. G., Dendy, R. O., Dieckmann, M. E., Ynnerman, A. and Chapman, Sandra C.. (2005) Surfatron and stochastic acceleration of electrons in astrophysical plasmas. Journal of Plasma Physics, Vol.71 (No.2). pp. 127-141. ISSN 0022-3778

Preview

PDF WRAP_Mcclements_surfratron_stochastic.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader Download (367Kb)

Abstract

Electron acceleration by large amplitude electrostatic waves in astrophysical plasmas is studied using particle-in-cell (PIC) simulations. The waves are excited initially at the electron plasma frequency $\omega_{\rm pe}$ by a Buneman instability driven by ion beams: the parameters of the ion beams are appropriate for high Mach number astrophysical shocks, such as those associated with supernova remnants (SNRs). If $\omega_{\rm pe}$ is much higher than the electron cyclotron frequency $\Omega_{\rm e}$, the linear phase of the instability does not depend on the magnitude of the magnetic field. However, the subsequent time evolution of particles and waves depends on both $\omega_{\rm pe}/\Omega_{\rm e}$ and the size of the simulation box $L$. If $L$ is equal to one wavelength, $\lambda_0$, of the Buneman-unstable mode, electrons trapped by the waves undergo acceleration via the surfatron mechanism across the wave front. This occurs most efficiently when $\omega_{\rm pe}/\Omega_{\rm e} \simeq 100$: in this case electrons are accelerated to speeds of up $c/2$ where $c$ is the speed of light. In a simulation with $L=4\lambda_0$ and $\omega_{\rm pe}/\Omega_{\rm e} = 100$, it is found that sideband instabilities give rise to a broad spectrum of wavenumbers, with a power law tail. Some stochastic electron acceleration is observed in this case, but not the surfatron process. Direct integration of the electron equations of motion, using parameters approximating to those of the wave modes observed in the simulations, suggests that the surfatron is compatible with the presence of a broad wave spectrum if $\omega_{\rm pe}/\Omega_{\rm e}> 100$. It is concluded that a combination of stochastic and surfatron acceleration could provide an efficient generator of mildly relativistic electrons at SNR shocks.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Plasma accelerators, Collisions (Astrophysics), Stochastic processes, Supernova remnants, Particles, Relativistic
Journal or Publication Title:	Journal of Plasma Physics
Publisher:	Cambridge University Press
ISSN:	0022-3778
Date:	April 2005
Volume:	Vol.71
Number:	No.2
Page Range:	pp. 127-141
Identification Number:	10.1017/S0022377804003514
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC), Universitetet i Linköping
References:	Achterberg, A. and Ball, L. 1994 Astron. Astrophys. 285, 687. Bell, A. R. 1978 Mon. Not. R. Astron. Soc. 182, 147. Bernstein, I. B., Greene, J. M. and Kruskal, M. D. 1957 Phys. Rev. 108, 546. Biermann, P. L. and Cassinelli, J. P. 1993 Astron. Astrophys. 277, 691. Bingham, R., Mendonça, J. T. and Shukla, P. K. 2004 Plasma Phys. Control. Fusion 46, R1. Blondin, J. M. and Lundqvist, P. 1993 Astrophys. J. 405, 337. Brunetti, M., Califano, F. and Pegoraro, F. 2000 Phys. Rev. E 62, 4109. Dieckmann, M. E., McClements, K. G., Chapman, S. C., Dendy, R. O. and Drury, L. O'C. 2000a Astron. Astrophys. 356, 377. Dieckmann, M. E., Ljung, P., Ynnerman, A. and McClements, K. G. 2000b Phys. Plasmas 7, 5171. Dieckmann, M. E., Eliasson, B., Stathopoulos, A. and Ynnerman, A. 2004a Phys. Rev. Lett. 92, 065006. Dieckmann, M. E., Eliasson, B. and Shukla, P. K. 2004b Phys. Plasmas 11, 1394. Hoshino, M. and Shimada, N. 2002 Astrophys. J. 572, 880. Karney, C. F. F. 1978 Phys. Fluids 21, 1584. Katsouleas T. and Dawson, J. M. 1983 IEEE Trans. Nuc. Science NS-30, 3241. Kruer, W. L., Dawson, J. M. and Sudan, R. N. 1969 Phys. Rev. Lett. 23, 838. McClements, K. G., Dieckmann, M. E., Ynnerman, A., Chapman, S. C. and Dendy, R. O. 2001 Phys. Rev. Lett. 87, 255 002. Mendonça, J. T. 1996 Physica Scripta T63, 136. Quest, K. B. 1986 J. Geophys. Res. 91, 8805. Schmitz, H., Chapman, S. C. and Dendy, R. O. 2002a Astrophys. J. 570, 637. Schmitz, H., Chapman, S. C. and Dendy, R. O. 2002b Astrophys. J. 579, 327. Scholer, M., Shinohara, I. and Matsukiyo, S. 2003 J. Geophys. Res. 108, 1014. Sckopke, N., Paschmann, G., Bame, S. J., Gosling, J. T. and Russell, C. T. 1983 J. Geophys. Res. 88, 6121. Shimada, N. and Hoshino, M. 2000 Astrophys. J. Lett. 543, L67. Tajima, T. and Dawson, J. M. 1979 Phys. Rev. Lett. 43, 267.
URI:	http://wrap.warwick.ac.uk/id/eprint/743

Request changes to a record

Actions (login required)

View Item