Large Amplitude Relativistic Electromagnetic Solitons in Intense Laser Pulse Interaction with Underdense Plasmas

Li Baiwen1), S.Ishiguro1,2), M.M.Skoric3), H.Takamaru 4)

1)The Graduate University for Advanced Studies, 322-6 Oroshi, Toki 509-5292, Japan
2)National Institute for Fusion Science, 322-6 Oroshi, Toki 509-5292,Japan
3)Vinca Institute of Nuclear Sciences, Belgrade 11001, Serbia and Montenegro
4)Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501, Japan

Relativistic solitons are electromagnetic (E.M.) structures self-trapped by a locally modified plasma refractive index through the relativistic electron mass increase and the electron density redistribution by the ponderomotive force of intense laser pulse. They are generated behind the laser pulse and are made of low-frequency, nonlinear, spatially localized E.M. fields. A fairly large part of the laser pulse energy can be transformed into E.M. solitons. The mechanism of soliton formation and the structure were analytically investigated and observed by particle simulation in underdense and overdense plasmas [1-3]. Recently, the research on solitons has received much attention because they are of fundamental importance for nonlinear science [4] and are considered to be the essential component of turbulence in plasmas [3]. We present the results on one-dimensional large-amplitude spatially localized relativistic E.M. solitons. The standing, backward- and forward-accelerated large amplitude relativistic E.M. solitons induced by a laser pulse propagation in long underdense homogeneous plasmas after multiple nonlinear interaction processes [3], are observed by means of 1D relativistic E.M. particle-in-cell (PIC) simulations. It was found that, in addition to the inhomogeneity of the plasma density, the acceleration of solitons depends upon, not only the intensity of the incident laser pulse, but also upon the plasma length. The frequency of the E.M. soliton wave was about one-half of the unperturbed plasma frequency. The electric field of solitons has the half-cycle structure in space, while the magnetic field and corresponding electrostatic field have the one-cycle structure. The backward- or forward-accelerated solitons propagate towards the plasma-vacuum interface where they radiate their energy in the form of intense low-frequency bursts of E.M. radiation.

References

[1] R.N. Sudan et al., Phys. Plasmas 4(5), 1489(1997); Lj. Hadzievski et al., Phys. Plasmas 9, 2569(2002); S. Poormakala et al., Phys. Plasmas 9, 1820(2002)
[2] A. Pukhov et al., Phys. Rev. Lett. 76, 3975(1996); S.V. Bulanov et al., Phys. Rev. Lett. 82, 3440(1999); T. Esirkepov et al., Phys. Rev. Lett. 89, 275002(2003)
[3] K. Mima et al., Phys. Plasmas 8, 2349(2001)
[4] V.E. Zakharov,S.V.Manakov et al., Theory of Solitons, Plenum Press, New York,1984