A Study of the Dynamic Interaction of a Plasmoid with a Magnetostatic Field Gradient from an Axial Current

摘要

The dynamic behavior of a plasmoid in a magnetostatic field having a gradient is investigated. The plasmoid is produced by a Bostick type twin electrode button source and the azimuthally symmetric magnetostatic field with a l/r dependence is produced by an axial current of up to 48 kA. The motion of such a plasmoid, projected in the transverse-to-B plane and in the direction of increasing field, is studied. We resolve the plasmoid motion into a motion in the plane transverse-to-B, and a motion along the field lines. The experimental observations reveal that in the transverse plane the plasmoid penetrates across the field lines while experiencing radial deceleration in its bulk (fluid) velocity, and a drift along the axial direction. The radial component of the fluid velocity of this plasma eventually reduces to zero at a turning point; the plasmoid then reverses its radial direction of motion and travels away from the axial current. Concurrently, the plasma spreads along the aximuthal field lines and drifts axially in the direction opposite to that of the axial drift of the plasma in the transverse plane. This plasma also forms a plasma-field interface cavity surrounding the axial current, and its boundary lies at the radial position of the turning point of the trajectory of the plasma in the transverse plane. (Author)