Simulation of geophysical phenomena in the laboratory

T exploration of has become more and more an investigation of plasma-magnetic field interaction. This is because consists primarily of plasma permeated by magnetic fields, and their mutual interactions give rise to the many geophysical phenomena observed on earth and more recently with space probes. Since the earliest times, these observations and measurements have stimulated or have been stimulated by theoretical deduction. Consequently, a considerable effort, which is continuing to increase, has been expended in attempts to explain the various phenomena. Because of the complexity of the interaction in nature, a number of assumptions are necessary in each theoretical derivation. It is usually difficult to ascertain whether the physical mechanisms that are crucial to each theory are the important ones in nature, or whether effects that have been neglected really determine what happens. More and more measurements, particularly those due to space probes, are beginning to produce significant data that can be used to resolve some of these aspects. One major difficulty is that the earth's environment is not a controlled environment, so that it is in many cases difficult to perform a true controlled experiment in space which may test a crucial feature of our understanding of a phenomenon, nor is a single measurement, no matter how precise, likely to be sufficient due to the cyclic (diurnal, sunspot, etc.) behavior of many natural phenomena. We are accumulating a considerable number of piecemeal observations but, as yet, no general unifying concept of the geophysical environment. One can then ask, could not scale model laboratory measurements provide considerable information on the applicability of various theories and consequently assist in the interpretation of full-scale data and perhaps suggest the design of future experiments? Over the last sixty Table 1 Comparison of parameters found in nature and in laboratory