Evolution of flux ropes in the magnetotail: A three-dimensional global hybrid simulation

Journal Article · Fri May 15 04:00:00 EDT 2015 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4919615· OSTI ID:22410327

Lu, S. ^[1]; Lin, Y.; Wang, X. Y. ^[2]; Huang, C.; Wu, M. Y.; Wang, S. ^[1]; Wang, R. S. ^[3]

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1. CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences, University of Science and Technology of China, Hefei (China)
2. Physics Department, Auburn University, Auburn, Alabama (United States)
3. Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing (China)

Flux ropes in the Earth's magnetotail are widely believed to play a crucial role in energy transport during substorms and the generation of energetic particles. Previous kinetic simulations are limited to the local-scale regime, and thus cannot be used to study the structure associated with the geomagnetic field and the global-scale evolution of the flux ropes. Here, the evolution of flux ropes in the magnetotail under a steady southward interplanetary magnetic field are studied with a newly developed three-dimensional global hybrid simulation model for dynamics ranging from the ion Larmor radius to the global convection time scales. Magnetic reconnection with multiple X-lines is found to take place in the near-tail current sheet at geocentric solar magnetospheric distances x=−30R{sub E}∼−15R{sub E} around the equatorial plane (z=0). The magnetotail reconnection layer is turbulent, with a nonuniform structure and unsteady evolution, and exhibits properties of typical collisionless fast reconnection with the Hall effect. A number of small-scale flux ropes are generated through the multiple X-line reconnection. The diameter of the flux ropes is several R{sub E}, and the spatial scale of the flux ropes in the dawn-dusk direction is on the order of several R{sub E} and does not extend across the entire section of the magnetotail, contrary to previous models and MHD simulation results and showing the importance of the three-dimensional effects. The nonuniform and unsteady multiple X-line reconnection with particle kinetic effects leads to various kinds of flux rope evolution: The small-scale flux ropes propagate earthward or tailward after formation, and eventually merge into the near-Earth region or the mid-/distant-tail plasmoid, respectively. During the propagation, some of the flux ropes can be tilted in the geocentric solar magnetospheric (x,y) plane with respect to the y (dawn-dusk) axis. Coalescence between flux ropes is also observed. At the same time, the evolution of the flux ropes in the multiple X-line reconnection layer can also lead to the acceleration and heating of ions.

• OSTI ID: 22410327
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 22; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACCELERATION
COALESCENCE
DISTANCE
ENERGY TRANSFER
GEOMAGNETIC FIELD
HALL EFFECT
HEATING
INTERPLANETARY MAGNETIC FIELDS
IONS
LARMOR RADIUS
MAGNETIC RECONNECTION
MAGNETOHYDRODYNAMICS
MAGNETOTAIL
THREE-DIMENSIONAL CALCULATIONS
TIME DEPENDENCE