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The links between magnetic reconnection, turbulence, and energy dissipation in the heliosphere.

Turbulence and magnetic reconnection are multiscale processes that convert energy from outer to inner scales. In the last decades, the improvement of observational and computational capabilities has suggested close links between turbulence and reconnection in Heliospheric and magnetospheric plasmas. Thanks to high-cadence and multi-spacecraft measurements, as well as large-scale computations, it has become possible to study the interplay between these fundamental processes across a broad range of scales, including electron-scales. This session welcomes contributions from observational, numerical and theoretical work, including new techniques and methods for characterising the links between reconnection and turbulence. Topics of interest include reconnection that occurs in turbulent systems, turbulence generated by reconnection events, the role of reconnection in the development of kinetic turbulence, and the influence of turbulence and reconnection on energy dissipation.

Convener: Jeffersson Andres Agudelo RuedaECSECS | Co-conveners: Julia StawarzECSECS, Tak Chu Li, Luca Franci, Robert Wicks
| Mon, 23 May, 17:45–18:30 (CEST)
Room 1.34

Mon, 23 May, 17:00–18:30

Chairpersons: Jeffersson Andres Agudelo Rueda, Tak Chu Li, Luca Franci


Oreste Pezzi

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.

Muni Zhou et al.

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.

Davide Manzini et al.

We derive the coarse-graining (CG) equations of  incompressible Hall Magnetohydrodynamics (HMHD) turbulence to investigate the local (in space) energy cascade rate as a function of the filtering scale. 
First, the CG equations are space averaged to obtain the analytical expression of the mean cascade rate. Its application to 3 dimensional (3D) simulations of (weakly compressible) HMHD shows a cascade rate consistent with the value of the mean dissipation rate in the simulations and with the classical estimates based on the "third-order" law.

 The strength of the CG approach is further revealed when considering the local-in-space energy cascade rate which is shown theoretically and numerically to match dissipative processes at a given position x, when both quantities are locally averaged over a small neighboring region (quasi-locality). This result supports the claim that the (quasi-)local cascade rate can provide a reliable estimate of the (quasi-)local energy dissipation, regardless of the nature of the dissipation processes involved.

The new model is further applied to magnetic reconnection sites observed in Hybrid-Vlasov (HVM) simulations and in spacecraft data. The results show the robustness of the new model over standard tools used to highlight energy dissipation processes and particles energization at the X points.  

How to cite: Manzini, D., Sahraoui, F., and Califano, F.: Local Cascade and Dissipation: The Coarse Graining approach as a robust tool to investigate Magnetic Reconnection, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7183, https://doi.org/10.5194/egusphere-egu22-7183, 2022.

Subash Adhikari et al.

Over the past few decades, the relationship between turbulence and reconnection has emerged as a subject of interest. For example, various properties of reconnection have been studied in different turbulent environments using plasma simulations. In other approaches, reconnection is studied as a subsidiary process occurring in turbulence. Turbulent features are also studied as consequences of instabilities associated with large scale reconnection. Only recently, we have attempted to answer some of the fundamental questions such as: “What are the turbulent-like features of laminar magnetic reconnection?”, "Is magnetic reconnection fundamentally an energy cascade?" both related to the interplay between reconnection and turbulence. Using 2.5D particle in cell simulations, we have found that laminar magnetic reconnection in a quasi-steady phase exhibits a Kolmogorov-like power spectrum. Most notably, the energy transfer process in magnetic reconnection is also found to be similar to that of a turbulent system suggesting that reconnection involves an energy cascade. The reconnection rate is correlated to both the magnetic energy spectrum in the ion-scales and the cascade of energy. Further, similarities between reconnection and turbulence in terms of the electric field spectrum, their components, and pressure-strain interaction will be highlighted.

How to cite: Adhikari, S., Shay, M. A., Parashar, T. N., Matthaeus, W. H., Sharma Pyakurel, P., Stawarz, J. E., and Eastwood, J. P.: Reconnection and Turbulence: A Qualitative Approach to their Relationship, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9828, https://doi.org/10.5194/egusphere-egu22-9828, 2022.

Yi Qi et al.

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.

Bogdan Hnat et al.

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.

Prayash Pyakurel et al.

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.

General Discussion