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Global hybrid (electron fluid, kinetic ions) and fully kinetic simulations of the magnetosphere have been used to show surprising interconnection between shocks, turbulence, and magnetic reconnection. In particular, collisionless shocks with their reflected ions that can get upstream before retransmission can generate previously unforeseen phenomen...
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Benefited from the high‐resolution measurements provided by Cluster and Magnetospheric Multiscale missions, there are abundant evidences demonstrating the existence of intermittent current sheets in the terrestrial magnetosheath downstream of a quasi‐parallel shock, where magnetic reconnection can occur. However, the process...
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... These assumptions often portray jets as either cylinder -, pancake-, or finger -like shapes, e xhibiting div erse sizes aligned in parallel or perpendicular directions to the plasma flow or magnetic field orientation (Archer et al. 2012 ;Karlsson et al. 2012 ;Plaschke et al. 2016Plaschke et al. , 2018Goncharov et al. 2020 ;Plaschke et al. 2020 ;Palmroth et al. 2021 ;Guo et al. 2022 ). In addition, all the previously applied kinetic models to investigate magnetosheath jets have either been two-dimensional (2D) models in the spatial domain (configuration space) (Gutynska et al. 2015 ;Omidi et al. 2016 ;Hao et al. 2016a ;Palmroth et al. 2018 ;Preisser et al. 2020 ;Palmroth et al. 2021 ;Suni et al. 2021 ;Guo et al. 2022 ) or three-dimensional (3D) models with reduced scales of the Earth (Karimabadi et al. 2014 ;Omidi et al. 2016 ;Ng, Chen & Omelchenk o 2021 ;Omelchenk o et al. 2021 ) or focused on a small region in the magnetosheath (e.g. Voitcu & Echim 2018 ). ...
... Moreo v er, jets have been observed more frequently when the IMF exhibits a higher level of stability (Savin et al. 2008 ;Hietala et al. 2009 ;Archer & Horbury 2013 ;Plaschke et al. 2013 ). This suggests that, in general, the formation of jets is not directly associated with IMF discontinuities or transient events such as magnetic discontinuities and hot flow anomalies Plaschke et al. 2013 ;Karimabadi et al. 2014 ;Suni et al. 2021 ;Raptis et al. 2022a ). ...
... Ho we ver, some of the hybrid models that have chosen cell sizes comparable to or smaller than δ i have scaled down the global physical size of the interaction region (e.g. Karimabadi et al. 2014 ;Her č ík et al. 2016 ;Omelchenko et al. 2021 ), and therefore the relative size of δ i to the interaction scale size is larger than the physical ratios. In all the simulation results presented here, we have used regular-spaced Cartesian cubic grids of size L = 500 km ( ≈0 . ...
Magnetosheath jets represent localized enhancements in dynamic pressure observed within the magnetosheath. These energetic entities, carrying excess energy and momentum, can impact the magnetopause and disrupt the magnetosphere. Therefore, they play a vital role in coupling the solar wind and terrestrial magnetosphere. However, our understanding of the morphology and formation of these complex, transient events remains incomplete over two decades after their initial observation. Previous studies have relied on oversimplified assumptions, considering jets as elongated cylinders with dimensions ranging from 0.1 RE to 5 RE (Earth radii). In this study, we present simulation results obtained from Amitis, a high-performance hybrid-kinetic plasma framework (particle ions and fluid electrons) running in parallel on Graphics Processing Units (GPUs) for fast and more environmentally friendly computation compared to CPU-based models. Considering realistic scales, we present the first global, three-dimensional (3D in both configuration and velocity spaces) hybrid-kinetic simulation results of the interaction between solar wind plasma and Earth. Our high-resolution kinetic simulations reveal the 3D structure of magnetosheath jets, showing that jets are far from being simple cylinders. Instead, they exhibit intricate and highly interconnected structures with dynamic 3D characteristics. As they move through the magnetosheath, they wrinkle, fold, merge, and split in complex ways before a subset reaches the magnetopause.
... Plasma flows play an important role in numerous applications in astrophysics, e.g., relativistic jets from active galactic nuclei [47], earth's magnetosphere [36,24,43,15], the solar wind [38,66,16]. Often, to simulate plasma flows, equations of Magnetohydrodynamics (MHD) are used. ...
In this article, we consider the Chew, Goldberger \& Low (CGL) plasma flow equations, which is a set of nonlinear, non-conservative hyperbolic PDEs modelling anisotropic plasma flows. These equations incorporate the double adiabatic approximation for the evolution of the pressure, making them very valuable for plasma physics, space physics and astrophysical applications. We first present the entropy analysis for the weak solutions. We then propose entropy-stable finite-difference schemes for the CGL equations. The key idea is to rewrite the CGL equations such that the non-conservative terms do not contribute to the entropy equations. The conservative part of the rewritten equations is very similar to the magnetohydrodynamics (MHD) equations. We then symmetrize the conservative part by following Godunov's symmetrization process for MHD. The resulting equations are then discretized by designing entropy conservative numerical flux and entropy diffusion operator based on the entropy scaled eigenvectors of the conservative part. We then prove the semi-discrete entropy stability of the schemes for CGL equations. The schemes are then tested using several test problems derived from the corresponding MHD test cases.
... Even though kinetic plasma simulations are becoming increasingly common in recent years and are being employed to even model global astrophysical scales (see e.g. Palmroth et al. (2023Palmroth et al. ( , 2018; Lapenta et al. (2022); Karimabadi et al. (2014) and references therein), construction of fluid models from the kinetic Boltzmann equation is still of crucial importance for a very large area of physical sciences, from the solar and astrophysical applications to laboratory studies of plasma fusion. It is worth noting that kinetic plasma simulations (particle-in-cell or Vlasov, fully kinetic or hybrid) are typically focused on almost collisionless plasmas by modeling the evolution of the Vlasov equation, with an assumption that the effects of collisions are subdominant, but where various stabilization mechanisms (which can be viewed as heuristic collisions), often have to be added to prevent numerical problems. ...
In our previous paper (Hunana et al. 2022) we have employed the Landau (Coulomb, Fokker-Planck) collisional operator together with the moment method of Grad and considered various generalizations of the Braginskii model, such as a multi-fluid formulation of the 21-and 22-moment models valid for general masses and temperatures, where all of the considered moments are described by their evolution equations (with fully non-linear left-hand-sides). Here we consider the same models, however, we employ the Boltzmann operator and calculate the collisional contributions via expressing them through the Chapman-Cowling collisional integrals. These "integrals" just represent a useful mathematical technique/notation introduced roughly 100 years ago, which (in the usual semi-linear approximation) allows one to postpone specifying the particular collisional process and finish all of the calculations with the Boltzmann operator completely. Additionally, by considering the cases of self-collisions and m a ≪ m b , we express all of the Braginskii transport coefficients through the Chapman-Cowling integrals as well. We thus offer a multi-fluid 22-moment model as well as the Braginskii model, which are valid for a large class of (elastic) collisional processes describable by the Boltzmann operator. The particular collisional process-the hard spheres, the Coulomb collisions, the Maxwell molecules, the inverse interparticle force ∼ 1/r^ν (or other cases not discussed here), are specified only at the end, by simply selecting few (pure) numbers. In the Appendix, we introduce the Boltzmann operator in a way suitable for newcomers and we discuss a surprisingly simple recipe how to calculate the collisional contributions with analytic software.
... This scenario could explain the observed dependence of the magnetosheath ion asymmetry on the upstream parameters as discussed in Section 3.2.1. Additionally, due to the curved shape of bow shock and magnetopause, the field line geometry in the magnetosheath can be very complicated (e.g., Karimabadi et al., 2014). The observed field-aligned asymmetry also depends on where the downstream field lines from spacecraft connect to, as suggested in the case studies and Figure 6. ...
The ion foreshock is highly dynamic, disturbing the bow shock and the magnetosphere‐ionosphere system. To forecast foreshock‐driven space weather effects, it is necessary to model foreshock ions as a function of upstream shock parameters. Case studies in the accompanying paper show that magnetosheath ions sometimes exhibit strong field‐aligned asymmetry toward the upstream direction, which may be responsible for enhancing magnetosheath leakage and therefore foreshock ion density. To understand the conditions leading to such asymmetry and the potential for enhanced leakage, we perform case studies and a statistical study of magnetosheath and foreshock region data surrounding ∼500 Time History of Events and Macroscale Interactions during Substorms mission bow shock crossings. We quantify the asymmetry using the heat flux along the field‐aligned direction. We show that the strong field‐aligned heat flux persists across the entire magnetosheath from the magnetopause to the bow shock. Ion distribution functions reveal that the strong heat flux is caused by a secondary thermal population. We find that stronger asymmetry events exhibit heat flux preferentially toward the upstream direction near the bow shock and occur under larger IMF strength and larger solar wind dynamic pressure and/or energy flux. Additionally, we show that near the bow shock, magnetosheath leakage is a significant contributor to foreshock ions, and through enhancing the leakage the magnetosheath ion asymmetry can modulate the foreshock ion velocity and density. Our results imply that likely due to field line draping and compression against the magnetopause that leads to a directional mirror force, modeling the foreshock ions necessitates a more global accounting of downstream conditions.
... Magnetosheath is a transition region between the bow shock and the magnetopause, which exhibits a variety of dynamical features and provides an ideal laboratory for studying turbulence and various kinds of magnetic structures (Breuillard et al., 2016;He et al., 2011;Huang, 2022;Huang, Du, et al., 2017;Huang et al., 2012Huang et al., , 2014Karimabadi et al., 2014;Sahraoui et al., 2003Sahraoui et al., , 2004Sahraoui et al., , 2006Tsurutani et al., 2011;Yordanova et al., 2008). Recent studies on turbulent dissipation within the magnetosheath provided formulae for dissipation rate spectra and presented dissipation rate spectra for kinetic turbulence (He et al., 2019(He et al., , 2020. ...
Plain Language Summary
The magnetosheath exhibits various dynamical features such as heating and compression of the plasma, kinetic instabilities, particle beams and kinetic structures due to the highly dynamical environment in near‐Earth space. The electron vortices as the structure that manifests the in suit observations, including bipolar variations of electron velocity and large electron vorticity, have been revealed widely in the magnetosheath. However, the specific effects of electron vortices embedded within the magnetic structures on these magnetic structures are still unknown, especially in a statistical view. Thanks to the unprecedented high‐time resolution data of the Magnetospheric Multiscale mission in the magnetosheath, we investigated the effects, including the nonideal electric fields, energy dissipation and magnetic fields, of electron vortices on these magnetic structures. We find that the nonideal electric fields, energy dissipation inside the electron vortices is more significant than outside for most of magnetic structures, and more than half of electron vortices have positive effects on generating the measured magnetic field of these magnetic structures, which is helpful for understanding the subsequent evolution and interaction between them.
... It has been observed that magnetic spectrum scaling exhibits Kolmogorov scaling of −5/3 in reconnection as well as in turbulence which provides evidence that reconnection dynamics involves energy transfer analogous to standard turbulence [26]. Several review articles discuss the way how turbulence can become the host of reconnecting current sheet and how reconnecting current sheet can drive turbulence [27][28][29][30]. ...
The Magnetospheric Multiscale Mission (MMS) has perceived whistler wave generation, coherent structures, and related turbulence close to the magnetopause reconnection zones. The current research examines coherent structure of whistler wave driven by an intense electron beam at the magnetopause's magnetic reconnection sites as well as by the dynamic growth of magnetic islands. A nonlinear model of high-frequency whistler wave and low-frequency magnetosonic wave has been developed by using the two-fluid approximation. Nonlinear dynamics of 3D whistler wave and magnetosonic wave have been solved by the pseudo spectral method along with the predictor-corrector method and finite difference method. The simulation's outcomes demonstrate the temporal and spatial development of the whistler localized structures and current sheets as a witness to the turbulence's existence. Moreover, the turbulent power spectra have been investigated. The formation of the thermal tail of energetic electrons has been studied using the power-law scaling of turbulence development. We determined the scale sizes of current sheets and localized structures using a semi-analytic model and showed that these scale sizes rely on the power of whistler wave. We predict that the acceleration of the energetic electrons and heating in the Magnetopause may be caused by whistler wave.
... Here we try to explore the possible relations between them. First, the quasiparallel bow shock shifts to the nose region if the IMF cone angle is close to 0°or 180°, which would lead to a more turbulent environment extending to the upstream foreshock region and downstream magnetosheath (Karimabadi et al., 2014b), and a closer location of the dayside bow shock to the Earth than the average (M. Wang et al., 2020). ...
The magnetopause deformation due to the upstream magnetosheath pressure perturbations is important to understand the solar wind‐magnetosphere coupling process, but how to identify such events from in situ spacecraft observations is still challenging. In this study, we investigate magnetopause crossing events with fast‐moving cold ions in the magnetosphere from Magnetospheric Multiscale observations, and find when fast‐moving cold ions are present at the magnetopause, they are closely associated with the magnetopause deformation, which is featured by fast magnetopause motion and significant magnetopause normal deflection from model predictions. Therefore, fast‐moving cold ions can be a useful indicator to search for magnetopause deformation events. By integrating the cold ion speed, the inferred magnetopause deformation amplitude varies from 0.1 to 2.0 RE. Further statistics indicate that such magnetopause deformation events prefer to occur under quasi‐radial interplanetary magnetic field and fast solar wind conditions, suggesting high‐speed magnetosheath jets could be one direct cause of magnetopause deformations.
... There is mounting evidence that in magnetized plasmas, magnetic reconnection, and turbulence are closely related. [19][20][21][22] The Earth's magnetosheath, magnetopause, and magnetotail are all potential sites for magnetic reconnection. 23,24 Many authors have explored how turbulence affects the rate of reconnection, specifically how turbulence already present might change Sweet-Parker reconnection and how turbulence may form because of reconnection. ...
Whistler waves have been studied for many years in relation to turbulence and particle heating, and observations show that they are crucial to magnetic reconnection. Recent research has revealed a close relationship between magnetic reconnection and turbulence. The current work investigates the whistler turbulence caused by the energetic electron beam in the magnetic reconnection sites of magnetopause and also due to dynamic evolution of magnetic islands. For this, we develop a model based upon the two-fluid approximation to study whistler dynamics, propagating in the medium with the pre-existing chain of magnetic islands and under the influence of background density perturbation originating from ponderomotive nonlinearity of wave. Dynamics of nonlinear whistler have been solved with pseudo-spectral approach and a finite difference method with a modified predictor–corrector method and a Runge Kutta method for the semianalytical model. In the current research, we study how the nonlinear whistler wave contributes to the significant space phenomenon, i.e., turbulence, localization, and magnetic reconnection. We have also investigated the formation of a current sheet in a magnetopause region of the order of few-electron inertial length. We analyzed the power spectrum at the magnetopause when the system reached a quasi-steady condition. Our new approach to study whistler turbulence by an energetic electron beam at the magnetic reconnection sites has extensive applications to space plasmas, shedding a new light on the study of magnetic reconnection in nature.
... The large scope of such models makes them computationally expensive, and exploring the massive parameter space associated with discontinuity-shock-interactions using global models is impractical. In addition, the focus of the previous studies has, with a few exceptions (e.g., Karimabadi et al., 2014), primarily been on either the formation of foreshock transients, or on the magnetospheric response to upstream discontinuities, leaving the topic of magnetic reconnection at the shock largely unexplored. ...
Recent simulations and in‐situ observations have shown that magnetic reconnection is an active dissipation mechanism in the transition region of collisionless shocks. The generation mechanisms and upstream conditions enabling reconnection have been studied numerically. However, these numerical studies have been limited to the case of a steady, uniform upstream. The effect upstream discontinuities have on shock reconnection remains poorly understood. Here, we use local hybrid (fluid electron, particle ion) simulations with time‐varying upstream conditions to study the influence upstream rotational discontinuities (RDs) have on the formation of reconnected magnetic structures in the shock transition region. Our results show that bursts of reconnection can occur when RDs interact with the shock. This effect is much more significant at initially quasi‐parallel shocks than quasi‐perpendicular shocks, as the interaction between the RDs and the foreshock (only present in the quasi‐parallel case) can lead to the generation of foreshock bubbles, in which we observe an enhanced reconnection occurrence. The enhanced fluxes of accelerated ions within the foreshock bubble are likely a contributing factor to the increased reconnection occurrence. In addition, we find that the RDs with large magnetic shear are prone to reconnect upon reaching the shock, resulting in the generation of large magnetic islands. Our findings illustrate that upstream discontinuities can significantly increase the amount of reconnected magnetic structures at the bow shock, suggesting that reconnection might be a particularly important dissipation mechanism during periods of dynamic upstream conditions.
... Second, the global MHD model does not address full dynamics in the magnetosheath and its surrounding areas. Magnetosheath temperature is heavily influenced by numerous kinetic processes such as magnetic islands, turbulent reconnection, ion-scale waves and turbulence, and magnetosheath jets (Karimabadi et al., 2014). In addition, the magnetosheath temperature is usually anisotropic, controlled by instabilities such as the mirror mode, firehose, and ion cyclotron, which maintain the magnetosheath plasma to marginal stability (Soucek et al., 2015). ...
