Yang Henglei( 杨恒磊 ),Wang Xiaogang( 王晓钢 ) State Key Laboratory of Materials Modification by Laser, Ion and Electron Beams; The Department of Physics; Dalian University of Technology Effects of Inflow Disturbance at Boundaries on the Magnetic Reconnection

Outline Driven reconnection Model Simulation results Summary and discussions

Magnetic reconnection usually happens in the magnetic confined plasmas as well as the planetary space plasma ; Magnetic fields embedded in plasmas undergo topological rearrangement due to nonideal instabilities or perturbations imposed at the boundary: ‘‘free’’ or ‘‘driven’’; Liberate free energy that can be converted to thermal and kinetic energy.

The sketch of reconnection

Ohm’s Law Collisional Ohm’s law Generalized Ohm’s Law

Outline Driven reconnection Model Simulation results Summary and discussions

Taylor model (Classical driven reconnection model) Fundamental model proposed by Taylor, and investigated by Hahm and Kulsrud is subjected to a boundary deformation: Xiaogang Wang.etc have made some researches and corrections on the model in the early work

Lc z x y ⊙y ⊙

Model (2 D 3 components MHD)

The initial magnetic fields : and:

, an inflow (in the units of ) is imposed The boundary conditions : Along the x direction, the periodical boundary conditions are imposed, i.e. the variables at the left boundary (x=0) correspond with the values at the right boundary (x=Lx=2) At z=0, the symmetric boundary conditions are taken use of

Fig. The inflow disturbance configuration

Outline Driven reconnection Model Simulation results Summary and discussions

CASE 1: is changed orderly Fig. the magnetic field figure when

Reconnection has happened Fig. the magnetic field figure (a) and velocity vector figure (b) at t=82 when

Fig. time history of magnetic reconnection rate trend under the different inflow velocities

Fig. the magnetic field figure (a) and velocity vector figure (b) at t=60 when CASE 2: is changed orderly

CASE 3: is changed orderly Fig. Comparison of the magnetic fields figures when

CASE 4: is changed orderly Fig. Comparison of the magnetic fields figures when

Outline Driven reconnection Model Simulation results Summary and discussions

) The faster the at boundaries is, 2) the closer its position (i.e. here) to the current sheet is, 3) the lower the viscosity is, 4) the higher the resistivity is, The faster the reconnection rate will be. Summary

The forced reconnection is caused by the driven inflow at the boundaries which bring the magnetic flux in as Owing to the resistivity in the current sheet, the magnetic lines are cut and reconnected again, and the magnetic islands are formed. Discussion

Reconnection is flow driven, increasing the inflow value and decreasing its distance to the current sheet will enhance its influence on reconnection; Furthermore the viscosity slows down the flow, therefore, reducing viscosity will strengthen the flow effect. Finally, the resistivity provides the dissipation, thus the larger the resistivity is, the easier the field lines reconnect. Discussion

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