Dynamics of moving electron vortices and magnetic ring in laser plasma interaction

Moving electron vortices have been observed in laser interaction with non-uniform near-critical-density plasma by multi-dimensional Particle-in-Cell simulations. In two dimensional geometry, there are two vortices with opposite magnetic polarity, moving perpendicularly to the plasma density gradient direction. The field distribution and particle motion composing such a moving structure have been clearly observed in simulations, which explains the vortex motion. Two components of loop currents are formed around each electron vortex, which dominate the vortex motion. The moving velocity can be as large as a 0.2 c level, forming relativistic vortices inside the plasma. Laser plasma conditions such as intensity, polarization, density profile, and external magnetic field effects on the vortex motion and evolution are also studied. In three dimensions, the structure appears as an expanding magnetic ring with an internal magnetic field up to 1000 Tesla. Such vortex structures suggest an interesting way of energy (with more than 5% of the laser energy) transportation to ambient plasmas as far as 50 μ m away from the laser-plasma interaction region, which may have applications in laser plasma-based inertial confinement fusion and laboratory astrophysics.