Plasma injection into a simulated magnetosphere

In an attempt to study the behavior of magnetospheric plasma, a laboratory ''terrella'' experiment was performed using a plasma emitter which was a newly designed small discharge tracer called Powered Double Probe (PDP). The tracer plasma was observed optically along the magnetic field line which crosses the PDP position. The configuration of the magnetic field lines which are deformed by the plasma kinetic energy is one of the most important features of such a system. This paper deals with the usefulness of the PDP and an experimental study of this plasma injection into the simulated magnetosphere in the absence of the interplanetary magnetic field (IMF). By discharging the PDP a luminous plasma was observed along the magnetic field lines of a pure dipole field (without plasma flow) and a distorted dipole field (simulated magnetosphere) like a flash bulb converting a time exposure camera into a time resolved camera. From these observations it is deduced that a deformation of magnetic field line at the nightside region, in a sense of a decreasing magnetic field, is a result of interaction between a plasma flow and a dipole field, but no neutral sheet region exists in the simulated magnetosphere in the range of 30 earth radii for zero IMF. Also no notable oscillation or instability of the magnetic field lines in the simulated magnetosphere were observed. This supports the possible existence of ''ground state'' of the actual magnetosphere which was defined by a theoretical study of substorm mechanism. (author)