Magnetic-dipole vortex generation by propagation of ultraintense and ultrashort laser pulses in moderate-density plasmas

Nakamura, Tatsufumi; Mima, Kunioki*

A magnetic dipole vortex is generated in the behind of an ultra-intense and ultra-short laser pulse in a near critical density plasma. The vortex is self-sustained by its magnetic field pressure which expels background cold electrons. This results in inducing a sheath field around the vortex which accelerates electrons to drive high amplitude electric current inside the vortex. The energy spectra of electrons accelerated in vortex shows non-thermal distribution with relatively high energy. The vortex is stable for a long period since it is in the electromagnetic equilibrium. The size of vortex and magnitude of electromagnetic fields are explained by a simple analytical model, which explains the characteristics of magnetic vortex in a wide parameter range. The results of analytical model show good agreements with 2D Particle-in-Cell simulation results. The high energy coupling of laser to electrons might be utilized for laser ion acceleration.