The nature of the processes responsible for the dissipation of energy in collisionless plasmas is an important open challenge in the field of space and astrophysical plasma physics. The solar wind is a prime example of a collisionless space plasma. Despite our efforts to measure these processes with spacecraft in the solar wind, we have not yet identified and quantified the relevant energy-transfer mechanisms successfully. Turbulence and magnetic reconnection are key candidates to explain the energy dissipation.

Using DiRAC’s high-performance-computing infrastructure, we design and analyse unprecedented three-dimensional particle-in-cell (PIC) simulations of anisotropic plasma turbulence under conditions like the plasma conditions in the solar wind (Agudelo Rueda et al., 2021). In our simulation domain, magnetic reconnection develops, which is a plasma process that transfers energy from the magnetic field to the plasma particles by re-structuring the field geometry. The high spatial resolution of our simulations allows us to study the energy transport and transfer between the electromagnetic fields and the plasma particles associated with reconnection events in great detail. Based on the moments of the kinetic Vlasov-Boltzmann equation, we evaluate proxy terms for the energy dissipation in these events.

We find that, in and around reconnection events, the thermal power density (heating) is greater than the kinetic power density (flow acceleration). The regions of intensified energy transfer extend along the direction of the background magnetic field, suggesting that a detailed three-dimensional analysis of the energy evolution is necessary (Agudelo Rueda et al., 2022). These results have major implications for our understanding of the geometry and distribution of the energy dissipation in turbulent space and astrophysical plasmas. In addition, our work informs the next generation of spacecraft analyses of the energy dissipation in the solar wind.

Sub-section of our simulation domain. Left: Kinetic power-density term (flow acceleration) for dissipation. Right: Thermal power-density term (heating) for dissipation. In the centres of the flux ropes, which form self-consistently in plasma turbulence, the energy transfer is enhanced. Heating occurs mostly along filamentary and elongated structures along the background magnetic field (vertical axis) and in the boundaries between the flux ropes. From Agudelo Rueda et al. (2022).


Agudelo Rueda, J. A., et al.: Three-dimensional magnetic reconnection in particle-in-cell simulations of anisotropic plasma turbulence, J. Plasma Phys. 87, 905870228, 2021, doi: 10.1017/S0022377821000404

Agudelo Rueda, J. A., et al.: Energy transport during 3D small-scale reconnection driven by anisotropic plasma turbulence, Astrophys. J., submitted, 2022

Categories: 2021 Highlights