Plasma Heating During Magnetic Reconnection: Implications for Turbulent Dissipation

Abstract:

Current sheets and associated intermittency are known to be prevalent in many turbulent plasmas and have been shown to be correlated with heating in observations of solar wind turbulence [1] and dissipation in kinetic particle-in-cell simulations [5]. Most intriguing, recent PIC simulations have found that the relative ion to electron heating ratio is strongly dependent on the turbulence amplitude [3]. An important question is whether magnetic reconnection is an important mechanism responsible for this heating. Studies focused on laminar reconnection have made significant progress recently on the magnitude and physics responsible for heating during magnetic reconnection [2,4]. The ambient Alfven speed of plasma flowing into the reconnection region plays a critical role, with heating initially taking the form of counterstreaming beams generated by non-local acceleration mechanism. However, there are significant uncertainties with how to link this basic reconnection heating with generic heating in a turbulent plasma. In this presentation, our current understanding of heating due to reconnection will be reviewed, and the factors determining the applicability of this heating to turbulent dissipation and heating will be discussed. These ideas will be explored through the comparison of kinetic PIC simulations of turbulence with reconnection heating models. Key aspects that will be examined are the effect of differing turbulent conditions on the magnitude and anisotropy of the heating, as well as the ion to electron heating ratio.

[1] Osman et al., ApJ Letters, 727, L11, 2011.

[2] Phan, et al., GRL, 40, 50917, 2013.

[3] Wu et al., ApJ Letters, 763, L30, 2013.

[4] Shay et al., Phys. Plasmas, 21, 122902, 2014.

[5] Wan et al., PRL, 114, 175002, 2015.