Role of Ion Kinetic Physics in the Interaction of Magnetic Flux Ropes

Stanier, Adam; Daughton, W.; Chacòn, Luis; Karimabadi, H.; Ng, Jonathan; Huang, Yi-Min; Hakim, Ammar; Bhattacharjee, A.

doi:10.1103/physrevlett.115.175004

Cited by 39 publications

(106 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, obarXiv:1611.07859v1 [physics.plasm-ph] 23 Nov 2016 servations suggest the local rate is 0.1, and the global rate can be at or below 0.1. This also has numerical support; in island coalescence, the global rate can be lower than 0.1 [38][39][40], while the local rate remains close to 0.1 [38].…”

mentioning

confidence: 86%

Why does Steady-State Magnetic Reconnection have a Maximum Local Rate of Order 0.1?

et al. 2017

Self Cite

View full text Add to dashboard Cite

Simulations suggest collisionless steady-state magnetic reconnection of Harris-type current sheets proceeds with a rate of order 0.1, independent of dissipation mechanism. We argue this long-standing puzzle is a result of constraints at the magnetohydrodynamic (MHD) scale. We perform a scaling analysis of the reconnection rate as a function of the opening angle made by the upstream magnetic fields, finding a maximum reconnection rate close to 0.2. The predictions compare favorably to particle-in-cell simulations of relativistic electron-positron and non-relativistic electron-proton reconnection. The fact that simulated reconnection rates are close to the predicted maximum suggests reconnection proceeds near the most efficient state allowed at the MHD-scale. The rate near the maximum is relatively insensitive to the opening angle, potentially explaining why reconnection has a similar fast rate in differing models. Introduction-Magnetic energy is abruptly released in solar and stellar flares [1][2][3], substorms in magnetotails of Earth and other planets [4,5], disruptions and the sawtooth crash in magnetically confined fusion devices [6], laboratory experiments [7], and numerous high energy astrophysical systems [8,9]. Magnetic reconnection, where a change in topology of the magnetic field allows a rapid release of magnetic energy into thermal and kinetic energy, is a likely cause. The reconnection electric field parallel to the X-line (where magnetic field lines break) not only determines the rate that reconnection proceeds, but can also be crucial for accelerating energetic superthermal particles. It was estimated that a normalized reconnection rate of 0.1 is required to explain time scales of flares and substorms [10].

show abstract

mentioning

confidence: 86%

Why does Steady-State Magnetic Reconnection have a Maximum Local Rate of Order 0.1?

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…Incompressibility (i.e., v C < c sA ) is compatible with (26) and (27) for M A ≈ 0.1 and c A < c sA . Equation (27) is notoriously in contrast with well-established Sweet and Parker's and Petschek's models of reconnection, as the latter predict much lower values of M A which, moreover, are decreasing functions of Lundquist number S. As for numerical simulations, fully kinetic computations only seem to be able to reproduce (27) to date [57] [58]. However, developing a theoretical understanding of (27) is a challenging task, which lies outside the aim of the present work.…”

Section: Merging Vs Bouncingmentioning

confidence: 67%

“…Indeed, the larger such velocity, the faster the change of magnetic flux, the larger the induced electric field and the corresponding dissipation, which is related to modifications of magnetic topology. The model does not depend on detailed knowledge of ion dynamics (which defies current fluid models [57] [69]), and leads to a simple rule-of-thumb: if the impact velocity is greater (less) than the product of Alfvèn speed times the global reconnection rate then merging (bouncing) occurs. Above threshold, dissipation slows down the relative motion of plasmoids until merging occurs.…”

Section: Discussionmentioning

confidence: 99%

“…A discussion of the dependence of the final outcome of scattering on the relative velocity requires detailed knowledge of momentum balance, which in turn depends on the motion of ions as m i ≫ m e . Generally speaking, the global evolution of the system depends on the ion pressure tensor, whose anisotropic and agyrotropic nature is due to the meandering orbits of ions and may not be correctly described in current fluid models [57] [69]. Fully kinetic simulations seem therefore to be useful [58] [60], Admittedly, however, their utilization in realistic, 3D problems is limited because of the computational resources required.…”

Section: Merging Vs Bouncingmentioning

confidence: 99%

See 1 more Smart Citation

On super-elastic collisions between magnetized plasmoids in the heliosphere

Vita

2018

Eur. Phys. J. D

View full text Add to dashboard Cite

Recently, a unique collision between two large-scale magnetized plasmoids produced by coronal mass ejections in the heliosphere has been observed [C. Shen et al., Nature Physics 8, 923-928 (2012)]. Results suggest that the collision is super-elastic, i.e. the total linear kinetic energy of the two plasmoids after the collision is larger than before the collision, and that an anti-correlation exists, i.e. the lower the initial relative velocity of the plasmoids, the larger the relative increase in total kinetic energy. The problemCoronal mass ejections (CMEs) give birth to large-scale plasmoids, originating from the solar atmosphere and expanding and propagating into the heliosphere [1] [2]. The occurrence rate of CMEs is about 4-5 CMEs per day at solar maximum [3], so that encounters and interactions between plasmoids are unavoidable. Nevertheless, inter-plasmoid collisions are far from understood. While collisions between blobs of ordinary gases are heavily affected by mixing, cross-field diffusion is effectively prohibited by sufficiently strong magnetic field.Experiments show that initially well-distinct plasmoids preserve their identity after a collision; historically, these experiments led to the very definition of 'plasmoid' as a 'plasma magnetic entity' with well-distinguished identity and geometrical structure [4]. In the lab, conventional magnetohydrodynamics fails to provide adequate macroscopic description of isolated plasmoids [5] -let alone their mutual interaction. In space, such description requires detailed knowledge of energy balance and state equation [2].Recent observation of a collision between plasmoids [1] suggests that such collisions may be superelastic, i.e. the total linear kinetic energy of the colliding plasmoids after the collision is larger than before the collision. A similar phenomenon is observed in collisions of spheres with elastoplastic plates, where rotational kinetic energy may be transferred into linear kinetic energy [6]. This analogy suggests that the linear kinetic energy in collisions between plasmoids may increase at the expense of the energy of some other degree of freedom, and magnetic energy is an obvious candidate. A preliminary investigation of energy balance supports this point of view; moreover, it has been suggested that the lower the impact velocity, the larger the relative increase of the linear kinetic energy [1]; in contrast, if the relative velocity of colliding plasmoids is too large, then no elastic scattering occurs [7], and the plasmoids may merge into each other.The aim of this work is to investigate this suggestion. We invoke the analogy [8] between plasmoids in the lab and space plasmoids and show how recent progress [5] [9] in the analytical description of the former provide information on the latter. In particular, we show that quantities usually invoked in Hall MHD [10] lead to a simple macroscopic description of interacting plasmoids. Some relevant properties of our plasmoids are discussed in Sec. 2. Secs. 3 and 4 discuss the structure...

show abstract

“…This is calculated by integrating along the x-axis starting from the X-point which lies at the origin. The reconnection rate (E R ) is calculated as [21] …”

Section: Reconnection Ratesmentioning

confidence: 99%

Two-way coupled MHD-PIC simulations of magnetic reconnection in magnetic island coalescence

Makwana

Keppens

Lapenta

2018

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

Abstract. We present simulations of magnetic reconnection with a newly developed coupled MHD-PIC code. In this work a global magnetohydrodynamic (MHD) simulation receives kinetic feedback within an embedded region that is modeled by a kinetic particle-in-cell (PIC) code. The PIC code receives initial and boundary conditions from the MHD simulation, while the MHD solution is updated with the PIC state. We briefly describe this coupling mechanism. This method is suitable for simulating magnetic reconnection problems, as we show with the example of reconnection in the coalescence of magnetic islands. We compare the MHD, Hall-MHD, fully PIC and coupled MHD-PIC simulations of the magnetic island coalescence. We find that the kinetic simulations are very different from the MHD and Hall-MHD results, while the coupled MHD-PIC simulations can remedy this discrepancy while saving computing time. The diffusion region is well resolved in the kinetic simulations, which is also captured by the coupled MHD-PIC model. The coupled simulation also reproduces the kinetic Hall magnetic fields correctly. We calculate the reconnection rates and find differences between the MHD and kinetic results. We find that the coupled MHD-PIC code can reasonably reproduce the kinetic reconnection rate when a larger PIC feedback region is used, while still saving significant computing time. IntroductionSimulating plasmas is a very challenging task because plasma processes are multi-scale as well as multi-physics in nature. For example, turbulence can be driven at large scales by fluid processes, like solar flares or some magnetohydrodynamic (MHD) instabilities. The nonlinear interactions at the high Reynolds and Lundquist numbers in space and astrophysical plasmas give rise to energy transfer to multiple scales, going right down to the ion and electron scales, which are several orders of magnitude smaller [1, 2] than the driving scales. In solar corona MHD processes operate at 10 9 m while electron scales lie at 10 −1 m [3]. Similarly in Earth's magnetosphere the solar wind driver operates at 10 9 m while electron scales lie at 10 3 m [4]. Simulating this range of scales is not possible even with the computing facilities of foreseeable future. However, an even greater challenge is that while the plasma can be treated as a fluid at the largest scales, the kinetic, particulate nature of plasma becomes critical at the small scales. MHD models are fluid models which work at scales larger than the ion gyroradius or skin depth [5] and are computationally ideal for global simulations. However, they do not capture the kinetic physics that results from the particulate nature of plasma. The Maxwell-Vlasov equations are typically used to describe a plasma kinetically and many advanced particle-in-cell (PIC) techniques have been developed to simulate them. However, these are significantly more

show abstract

Role of Ion Kinetic Physics in the Interaction of Magnetic Flux Ropes

Cited by 39 publications

References 39 publications

Why does Steady-State Magnetic Reconnection have a Maximum Local Rate of Order 0.1?

Why does Steady-State Magnetic Reconnection have a Maximum Local Rate of Order 0.1?

On super-elastic collisions between magnetized plasmoids in the heliosphere

Two-way coupled MHD-PIC simulations of magnetic reconnection in magnetic island coalescence

Contact Info

Product

Resources

About