Experiments in a Magnetically Driven Shock Tube with an Axial Magnetic Field

Experiments in a magnetically driven annular shock tube with hydrogen as test gas, with an axial magnetic field are reported. The initial pressure (50–500 μ), axial field (0–0.45 Wb/m2), and drive field (0.8–1.0 Wb/m2) were chosen to produce shock speeds and test times such that separation between shock front and current sheet was predicted. Measurements of magnetic and electric fields and intensity of continuum radiation showed that shock front and current sheet coincided both in the regimes where a gas-dynamic shock and a magnetohydrodynamic switch-on shock were predicted. Shock Alfvén Mach numbers covered the range 1.2 to 7.2. Axial and azimuthal momentum balances indicated that snowplow-type models adequately predict the shock tube performance. A radial electric field was measured upstream of the front when the Alfvén Mach number was in the switch-on regime, indicating that a model based on ionizing shock waves is more appropriate for predicting the flow pattern.