Contribution of Magnetic Reconnection Events to Energy Dissipation in Space Plasma Turbulence

Abstract

By analyzing the magnetosheath measurements from the Magnetospheric Multiscale Spacecraft, we obtain statistical results for the contribution of magnetic reconnection (MR) events at electron scales to the energy dissipation of coherent structures in shocked turbulent plasmas. The partial variance of increments (PVI) method is employed to find coherent structures in the magnetic field data. We consider criteria to further identify MR events, such as reversal of magnetic field components, significant energy dissipation, and evident electron outflow velocity. Statistically, for most MR events, their PVI values are larger than those of other types of coherent structures, and their energy dissipations are also stronger. However, due to the relatively small number of MR events, their contribution to coherent structures’ energy dissipation is relatively trivial. If the dissipation of non-coherent structures is taken into account, MR’s contribution to energy dissipation would be even less. Hence, we suggest that MR events, though having strong dissipation locally, are not the major contributor to energy dissipation in the turbulent magnetosheath. After analyzing the features of non-MR current sheets, we propose that these are mainly coherent structures inherent to kinetic Alfvén fluctuations.

Turbulence-driven magnetic reconnection and the magnetic correlation length: Observations from Magnetospheric Multiscale in Earth's magnetosheath

“…ergy, provides an estimate for the total amount of energy dissipation that is facilitated by the reconnection process either at the reconnection site or through secondary processes excited in the coherent reconnection outflow region. These estimates are somewhat distinct in perspective, but perhaps complimentary, to recent estimates of the energy dissipation associated with magnetic reconnection inferred from the locally observed J • E ′ in one interval of magnetosheath turbulence that seem to suggest that reconnection makes a minor contribution to dissipation 135 . The apparent discrepancy may be associated with variability across magnetosheath intervals, as is apparent in the range of values in the estimates above, or could potentially be cause by spatially nonuniform dissipation across the entire reconnection outflow region, which may be challenging to infer from only a limited number of reconnection events encountered in a given interval.…”

Formation of solar coronal loops through magnetic reconnection in an emerging active region

“…Our observed spectral indexes of about -1 indicate that the fluctuations fall in the energy containing range outside the inertial range with cascading process in the traditional turbulence scenario (Verscharen et al 2019). The observed power-law spectrum (∼f −1 ) suggests that the occurrence of reconnection events is randomly intermittent instead of driven by the turbulence with nonlinear interactions between vortices (Yang et al 2020;Hou et al 2021). Assuming that the reconnection inflow speed can be approximated as half of the converging speed and taking a typical speed of the plasma blobs as the outflow speed, we can roughly estimate the reconnection rate as 0.2/100=0.002.…”

Spatial Distribution and Low-frequency Disturbance Modulation of Magnetosheath Ion Polytropic Index

“…This result is reasonable because polytropic processes are not only affected by free energy but also modulated by waves, intermittent structures (such as vortices and current sheets), and other nonadiabatic processes, which are different in different regions of the turbulent magnetosheath (Huang et al 2014;He et al 2019He et al , 2020Wang et al 2019;Zhu et al 2019Zhu et al , 2020Hou et al 2021). The solar wind flows in front of the bow shock are basically radially outward from the Sun, whereas the interplanetary magnetic field they carry can possibly be in any direction.…”