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Ma, Z. W.

Publications and source records attributed to Ma, Z. W..

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Linear and nonlinear benchmarks between the CLT code and the M3D-C1 code for the 2/1 resistive tearing mode and the 1/1 resistive kink mode

Here, the linear and nonlinear benchmarks between the CLT code and the M3D-C1 code for the 2/1 resistive tearing mode and the 1/1 resistive kink mode are presented. CLT is an explicit finite difference code, while M3D-C1 is an implicit finite element code. Although the implementations of CLT and M3D-C1 are totally different, we find that the simulation results of the resistive-kink mode and the m/n=2/1 tearing mode from M3D-C1 and CLT are almost the same, including the linear and nonlinear growth rates, the mode structures, the nonlinear saturation levels, the Poincare plots, and the scaling laws. This confirms that the nonlinear results for the 1/1 resistive-kink mode and 2/1 tearing mode are accurate and reliable.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1994

Kinetic Alfven waves as a source of plasma transport at the dayside magnetopause

As the shocked solar wind with variable plasma density and magnetic field impinges on the dayside magnetopause, it is likely to generate large-scale Alfven waves at the solar wind magnetosphere interface. However, large gradients in the density and magnetic field at the magnetopause boundary effectively couple large-scale Alfven waves with kinetic Alfven waves may play an important role in plasma transport at the dayside magnetopause and in electron acceleration along field lines. The transport can occur because, unlike the magnetohydrodynamic (MHD) shear Alfven wave, the kinetic Alfven wave has an associated parallel electric field which breaks down the 'frozen-in' condition and decouples the plasma from field lines. We calculate the average deviation of the plasma from the field line from which we estimate the diffusion coefficient associated with these 'bundles' of lead to acceleration of electrons along field lines in the magnetopause boundary and may possibly provide an explanation for observed counterstreaming electron beams characterized by energies of 50-200 eV.

Lee, L. C.↗
NASA NTRS1994

Core magnetic field enhancement in single X line, multiple X line and patchy reconnection

Magnetic flux transfer events often show a significant increase of the magnetic field strength at the center of the events. Similar magnetic field observations have been reported for structures in or near the plasma sheet of the magnetotail at about 20 R(sub E). We have carried out two-dimensional (2D) and three-dimensional (3D) and simulations of single X line reconnection (SXR), multiple X line reconnection (MXR), and patchy reconnection to determine and compare the amplification of the magnetic field in the center of the developing flux tubes. The various processes are achieved by appropriate choices of 2D or 3D resistivity models. The simulations show that the increase in magnetic field strength depends on both the property of the initial configuration and the particular reconnection geometry. For the chosen initial conditions the MXR process leads to a larger increase in the core magnetic field than the patchy reconnection and SXR caused by larger magnetic tensions in the MXR process. The 3D processes always lead to a larger amplification than the corresponding 2D processes. In the 3D cases, force imbalance in the y direction will accelerate plasma out of the flux tube. This process reduces the thermal pressure and leads to a further compression of the flux rope, which yields an additional increase in the interior magnetic field strength.

Ma, Z. W.↗
NASA NTRS1993

Topology of magnetic flux ropes and formation of fossil flux transfer events and boundary layer plasmas

A mechanism for the formation of fossil flux transfer events and the low-level boundary layer within the framework of multiple X-line reconnection is proposed. Attention is given to conditions for which the bulk of magnetic flux in a flux rope of finite extent has a simple magnetic topology, where the four possible connections of magnetic field lines are: IMF to MSP, MSP to IMF, IMF to IMF, and MSP to MSP. For a sufficient relative shift of the X lines, magnetic flux may enter a flux rope from the magnetosphere and exit into the magnetosphere. This process leads to the formation of magnetic flux ropes which contain a considerable amount of magnetosheath plasma on closed magnetospheric field lines. This process is discussed as a possible explanation for the formation of fossil flux transfer events in the magnetosphere and the formation of the low-latitude boundary layer.

Lee, L. C.↗
NASA NTRS1991

A simulation study of impulsive penetration of solar wind irregularities into the magnetosphere at the dayside magnetopause

The impulsive penetration processes that occur when a plasma irregularity in the magnetosheath, modeled as a field-aligned filament, impinges on the dayside magnetopause, are investigated via a 2D magnetohydrodynamic code. It is found that, when the magnetic fields of the magnetosheath and magnetosphere are parallel or antiparallel, even plasma filaments with small initial velocities can eventually penetrate through the magnetopause and enter the magnetosphere. If the magnetic fields are not aligned, penetration will occur only if the initial kinetic energy density of the plasma filament is more than 50 times larger than the magnetic energy density due to the transverse component of the magnetic field.

Ma, Z. W.↗
NASA NTRS1991

Different FTE signatures generated by the bursty single X line reconnection and the multiple X line reconnection at the dayside magnetopause

This paper examines magnetic signatures associated with the time-dependent magnetic reconnection processes at the dayside magnetopause, using two-dimensional compressible MHD simulations. Emphasis is placed on the different flux-transfer-event (FTE) signatures generated by the bursty single X-line reconnection (BSXR) and the multiple X-line reconnection processes. It is shown that the FTE magnetic signatures are not exhibited on the magnetospheric side if the FTEs are due to the BSXR process and the ratio between the magnetic field strength in the magnetosheath to that in the magnetosphere is not less than 1.7. The simulation results are compared with satellite observations.

Ding, D. Q.↗