Speaker
R. Bingham
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.4014.pdf
Electron acceleration and maser radiation from collisionless shocks
R. Bingham1,2, D.C. Speirs1, K. Ronald1, A. Rigby3, R. Bamford2,3, R. A. Cairns4,
A.D.R. Phelps1, M. E. Koepke5, B. J. Kellett2, L. O. Silva6, S. Lebedev7, G. Gregori3
1Department of Physics, SUPA, University of Strathclyde, Glasgow, G4 0NG, U.K.
2Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, England, OX11 0QX, U.K.
3Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, U.K.
4School of Mathematics and Statistics, University of St. Andrews, Fife, Scotland, KY16 9SS,
U.K.
5Department of Physics, West Virginia University, Morgantown, WV 26506-6315, U.S.A.
6GoLP/Instituto de Plasmas e Fusau Nuclear, Instituto Superior Tecnico,
Universidade de Lisboa, 1049-001 Lisbon, Portugal
7Imperial College London, London, SW72AZ, U.K.
In this paper we describe a model of electron energization and cyclotron-maser emission
applicable to astrophysical magnetised collisionless shocks. It is inspired by the work of
Begelman, Ergun and Rees [1] who argued that the cyclotron maser instability occurs in
localised magnetised collisionless shocks such as those expected in Blazar jets. We report on
two recent laboratory experiments and numerical simulations carried out to investigate
electron acceleration at collisionless shocks and the maser radiation mechanism [2][3][4].
We describe how electrons accelerated by lower-hybrid waves at collisionless shocks
generate cyclotron-maser radiation when the accelerated electrons move into regions of
stronger magnetic fields. Magnetic compression and conservation of magnetic moment lead
to the formation of an electron velocity distribution having a horseshoe shape as the electrons
are accelerated along the magnetic field. Under certain conditions the horseshoe electron
velocity distribution is unstable to the cyclotron maser instability. Electron ring distributions
are also unstable to cyclotron maser emission and we show that such distributions can also be
generated at collisionless magnetised shocks.
[1] M. C. Begelman, R. E. Ergun, and M. J. Rees, Astrophys. J. 625, 51 (2005).
[2] F. Cruz et al., Physics of Plasmas 24, 022901 (2017).
[3] D. C. Speirs et al., Phys. Rev. Lett. 113, 155002 (2014).
[4] K. Ronald et al., Physics of Plasmas 15, 056503 (2008).
