Current driven kinetic Alfven instabilities in the solar atmosphere

We study two physical mechanisms that can cause anomalous dissipation of currents in the solar atmosphere. The first one is a resonant kinetic instability of ion-cyclotron kinetic Alfvén waves (ICKAWs) driven by currents flowing parallel or perpendicular to the background magnetic field [1]. These currents can be generated by coronal magnetic shears or plasma non-uniformity, or by MHD wave phase mixing. Since the frequencies of the excited ICKAWs are close to the proton cyclotron frequency, the inverse turbulent cascade transports the wave energy to lower frequencies where the waves can induce transversal heating of heavier ion species by the ion-cyclotron resonant interaction. Another, non-resonant instability of low-frequency KAWs, can be excited by electrons due to their acceleration in the electric field which is parallel to the magnetic field. Strong, super-Dreicer electric fields, which are required for this instability, can be generated during magnetic reconnection events in the solar atmosphere (flares, micro- and nanoflares). This non-resonant KAW instability can produce low-frequency pulsations of plasma emission, as is observed during solar flares. Both resonant and non-resonant instabilities excite waves with very short transversal wavelengths of the order of the ion gyroradius. This makes these waves accessible for the plasma heating and stochastic ion acceleration across the magnetic field. Both mechanisms transform the energy of currents into the perpendicular energy of ions. The scattering of current electrons by waves results in anomalous transport coefficients and fast energy release. The large transversal temperatures of ions in the places where the energy is released could serve as a signature for these processes.