A scale model laboratory experiment simulating the effect of the solar wind on the magnetosphere has been performed. On the basis of photographic and magnetic field measurements, two distinct types of interactions, depending on the properties of the solar wind, can be distinguished. The ‘standoff’ interaction shows a complete standoff of the impinging solar wind plasma at several earth radii away from the terrella. No visible injection of the ‘wind’ into the region of the terrella is observed. A very steep gradient of the magnetic field at the position of the standoff and the formation of discrete inner regions of plasma are found. The ‘injection’ interaction is characterized by the injection at high latitudes of plasma into the vicinity of the terrella merging into a single wake or tail. The visible plasma regions to windward generally exhibit considerable radial thickness and diffuse edges. Magnetic measurements show a much more gradual compression of the magnetic field and no discrete inner regions.

Under specific circumstances, the v.l.f. receiver (400 Hz–10 kHz) aboard the Alouette I spacecraft has observed an interference signal originating with an electrical converter system. The chief characteristics of this signal are that it appears only in daylight operation and is spin modulated in such a manner that signal nulls appear when the spacecraft is oriented for minimum V × B effects. To explain these features, a mechanism was postulated which involves a coupling of the converter signals via the power-supply internal impedance and the solar-cell chain to the plasma environment and thus to the v.l.f. antenna, but requiring the asymmetry of the V × B sheaths for coupling. In order to test the validity of this theory, a simple satellite model was immersed in a low-density plasma, and operations under different space conditions were simulated. It was shown that the system design of the spacecraft could permit observation of such an interference signal under the required conditions.

Ness [1965] has recently summarized the information available on the existence of a lunar magnetic field and the influence of such a field on the earth's environment. In addition he presented Imp 1 data on the lunar wake as evidence for an equatorial lunar magnetic field of several hundred gammas or more. It is the purpose of this note to show preliminary results obtained with laboratory simulation techniques on the form of the lunar magnetospheric cavity that may be formed if the moon exhibits a dipole magnetic field. Using the techniques developed previously for laboratory studies of the solar‐wind earth‐magnetosphere interaction [Osborne et al., 1964], a simulation study has been made with the ‘lunette’ magnetic field scaled to produce a windward magnetospheric boundary about 0.5 model radii from the surface. In the relatively weak (if any) magnetic field of the moon, the ion cyclotron radius of solar‐wind particles will be comparable to the lunar radius. This is the case in the model experiments described here. Scaling considerations and, in particular, the influence of the ion cyclotron radius are treated in detail in a forthcoming publication [Osborne et al., 1965]. No simulated interplanetary field is involved in these investigations.

A controlled plasma–magnetic field interaction has been achieved, the conditions of which are such as to fulfill generally the scaling considerations of some aspects of geophysical phenomena, in particular the initial commencement of a magnetic storm. The preliminary measurements indicate the sweeping action on a magnetic field by a moving plasma; the formation of a magnetic cavity; the motion of the "dip pole" under perturbed conditions; the stand-off of plasma; a quasi Van Allen belt whose drift westward can be suggested as a ring current mechanism; and a polar trapping region. The correlations between the laboratory observations, geophysical measurements, and related theories, where possible, show no serious discrepancies as yet.

This paper describes a fast-acting ~nicrowave diagnostic system which was developed for use with non-repetitive plas~nas, such as those in shocl; tubes and pulsed discharges, and which has proved i~seful in a wide variety of experimental configurations. The system may be used for either reflection or trans~nission measurements and gives a polar display of phase and amplitude in conjunction with timing marks. Sorile of the principal features are wide dynamic range, expansion of high attenuation regions of the display, and a presentation of data which is readily assessed visually. The system has been used a t microwave frequencies of 9.2 ki\/Ic, 9.7 bMc, 23.5 IcMc, and 34.5 kRiIc, with sa~npling periods from 0.1 msec to 0.1 psec a t 507, duty cycles.