Vlasov – Maxwell, Self-consistent Electromagnetic Wave Emission Simulations in the Solar Corona

Abstract

1.5D Vlasov-Maxwell simulations are employed to model electromagnetic emission generation in a fully self-consistent plasma kinetic model for the first time in the solar physics context. The simulations mimic the plasma emission mechanism and Larmor drift instability in a plasma thread that connects the Sun to Earth with the spatial scales compressed appropriately. The effects of spatial density gradients on the generation of electromagnetic radiation are investigated. It is shown that 1.5D inhomogeneous plasma with a uniform background magnetic field directed transverse to the density gradient is aperiodically unstable to Larmor-drift instability. The latter results in a novel effect of generation of electromagnetic emission at plasma frequency. When density gradient is removed (i.e. when plasma becomes stable to Larmor-drift instability) and a $low$ density, super-thermal, hot beam is injected along the domain, in the direction perpendicular to the magnetic field, plasma emission mechanism generates non-escaping Langmuir type oscillations which in turn generate escaping electromagnetic radiation. It is found that in the spatial location where the beam is injected, the standing waves, oscillating at the plasma frequency, are excited. These can be used to interpret the horizontal strips observed in some dynamical spectra. Quasilinear theory predictions: (i) the electron free streaming and (ii) the beam long relaxation time, in accord with the analytic expressions, are corroborated via direct, fully-kinetic simulation. Finally, the interplay of Larmor-drift instability and plasma emission mechanism is studied by considering $dense$ electron beam in the Larmor-drift unstable (inhomogeneous) plasma. http://www.maths.qmul.ac.uk/~tsiklauri/movie1.mpg * http://www.maths.qmul.ac.uk/~tsiklauri/movie2.mpg * http://www.maths.qmul.ac.uk/~tsiklauri/movie3.mpg