A fresh look on the heating mechanisms of the Solar corona
  Recently using Particle-In-Cell simulations i.e. in the kinetic plasma description Tsiklauri et al. and G\'enot et al. reported on a discovery of a new mechanism of parallel electric field generation, which results in electron acceleration. In this work we show that the parallel (to the uniform unperturbed magnetic field) electric field generation can be obtained in much simpler framework using ideal Magnetohydrodynamic (MHD) description, i.e. without resorting to complicated wave particle interaction effects such as ion polarisation drift and resulting space charge separation which seems to be an ultimate cause of the electron acceleration. Further, in the context of the coronal heating problem a new {\it two stage mechanism} of the plasma heating is presented by putting emphasis, first, on the generation of parallel electric fields within {\it ideal MHD} description directly, rather than focusing on the enhanced dissipation mechanisms of the Alfv\'en waves and, second, dissipation of these parallel electric fields via {\it kinetic} effects. It is shown that a single Alfv\'en wave harmonic with frequency ($\nu = 7$ Hz), (which has longitudinal wavelength $\lambda_A = 0.63$ Mm for putative Alfv\'en speed of 4328 km s$^{-1}$) the generated parallel electric field could account for the 10% of the necessary coronal heating requirement. We conjecture that wide spectrum (10$^{-4}-10^3$ Hz) Alfv\'en waves, based on observationally constrained spectrum, could provide necessary coronal heating requirement. 
David Tsiklauri