ST1.12

Understanding the dissipation of energy and the associated heating in weakly collisional turbulent plasmas represents still an unresolved challenge. Here we examine an ensemble of parameters commonly adopted to characterize processes of energy dissipation and conversion in plasmas by means of hybrid Vlasov-Maxwell simulations describing plasma turbulence at sub-proton scales in the whole six-dimensional phase-space.

We make a distinction between ``energy-based'' and ``distribution-function'' based parameters. The first class is related to energy transfer mechanisms, while the second one requires exact knowledge of the particle distribution function in velocity space. All these measures highlight that energy dissipation occurs inhomogeneously and close to regions that are characterized by intense magnetic stresses. The dependence of these processes with respect to the proton β parameter is finally explored. 

How to cite: Pezzi, O.: Turbulent dissipation in weakly-collisional plasmas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12164, https://doi.org/10.5194/egusphere-egu22-12164, 2022.

We report analytical and numerical investigations of sub-ion scale turbulence in weakly collisional, low beta plasmas using a hybrid fluid-kinetic model. In the isothermal limit, the same scalings for the energy spectrum and for the eddy anisotropy can be obtained from two distinct approaches: (i) tearing-mediated energy cascade (Loureiro & Boldyrev 2017), and (ii) intermittency corrections, arising from magnetic and density fluctuations concentrated mostly in two-dimensional structures (Boldyrev & Perez 2012). Our numerical results indicate that the latter case is the more plausible in this regime. With the inclusion of electron kinetic physics, the energy spectrum is found to steepen due to electron Landau damping, which is enabled by the local weakening of nonlinearities in current sheets, and yields significant energy dissipation in the velocity space. The use of a Hermite formalism to express the velocity space dependence of the electron distribution function allows us to obtain an analytical, zeroth-order solution for the Hermite moments of the distribution, which is borne out by numerical simulations.

How to cite: Zhou, M., Liu, Z., and Loureiro, N. F.: Kinetic-Alfvén-wave turbulence in the low beta limit: role of current sheets and electron Landau damping, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13243, https://doi.org/10.5194/egusphere-egu22-13243, 2022.

Magnetic reconnection plays an important role in converting energy while modifying the field topology. This process takes place under various plasma conditions during which the transport of magnetic flux is intrinsic. Identifying active magnetic reconnection sites with in-situ observations is challenging. A new technique, Magnetic Flux Transport (MFT) analysis, has been developed recently and proven in numerical simulation for identifying active reconnection efficiently and accurately. In this study we examine the MFT process in 37 previously reported electron diffusion region (EDR)/reconnection-line crossing events at the dayside magnetopause, in the magnetotail and magnetosheath using Magnetospheric Multiscale (MMS) measurements. The co-existing inward and outward MFT flow at the X-point provides a signature that magnetic field lines become disconnected and reconnected. The application of MFT analysis to in-situ observations demonstrates that MFT can successfully identify active reconnection sites under symmetric, asymmetric, and turbulent upstream conditions, providing a also higher rate of successful identification than plasma outflow jets alone.

How to cite: Qi, Y., Li, T. C., Russell, C., Ergun, R., Jia, Y., and Hubbert, M.: Magnetic Flux Transport Identification of Active Reconnection: MMS Observations in the Earth’s Magnetosphere, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3262, https://doi.org/10.5194/egusphere-egu22-3262, 2022.

Multipoint in-situ Cluster observations of the solar wind are analysed to identify the magnetic field line topology and current density of turbulent structures using magnetic field gradient tensor invariants. Identified structures are classified as actively evolving if their magnetic field varies significantly from the force-free configuration. We find that at least 35% of all structures are both actively evolving and carrying the strongest currents, actively dissipating, and heating the plasma. These structures are comprised of 1/5 3D plasmoids, 3/5 flux ropes, and 1/5 3D X-points consistent with magnetic reconnection. Actively evolving and passively advecting structures are both close to log-normally distributed. This provides direct evidence for the significant role of strong turbulence, evolving via magnetic shearing and reconnection, in mediating dissipation and solar wind heating.

How to cite: Hnat, B., Chapman, S., and Watkins, N.: Magnetic topology of actively evolving and passively convecting structures in the turbulent solar wind, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4139, https://doi.org/10.5194/egusphere-egu22-4139, 2022.

In the Earth’s turbulent magnetosheath downstream of the quasiparallel bow shock region, magnetic reconnection without ion coupling was observed with bi-directional super-Alfvénic electron jets. The lack of ion coupling was attributed to the small-scale sizes of the current sheets. In an electron-only reconnection event that occurred on 26 December 2016, we examine the detailed properties of electron inflows observed by all 4 MMS spacecraft. Even though the farthest MMS probe in the outflow direction from the X-line was no more than 8 electron skin depth, the electron inflows have significant asymmetry and highly variable amplitudes. We compare MMS observations with 2D-kinetic PIC simulation and find that the asymmetry in the inflow stems directly from the tilt of the out-of-plane (guide) magnetic field structure in the reconnection plane, with inflow asymmetry enhanced in the downstream region.

How to cite: Pyakurel, P., Phan, T., Shay, M., Stawarz, J., Øieroset, M., Cassak, P., Haggerty, C., Drake, J., Li, T. C., Burch, J., Ergun, R., Gershman, D., Giles, B., Torbert, R., Strangeway, R., and Russell, C.: On the short-scale spatial variability of electron inflows in electron-only magnetic reconnection in the turbulent magnetosheath observed by MMS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10186, https://doi.org/10.5194/egusphere-egu22-10186, 2022.