A structure of the Jovian magnetospheric boundary region near the equatorial plane which is produced by the interaction between the solar wind plasma and the internal planetary wind plasma in the magnetodisc, has been studied. A possibility of the existence of the internal shock, as a innermost boundary between the planetary wind and the region of the intrinsic magnetic field, has been investigated theoretically using two dimensional Rankine-Hugoniot relation in MHD regime. The results of present numerical calculation for the internal shock indicate the asymmetrical characteristics; that is, the internal shock is strong in the dawn side of the Jovian magnetodisc, while the shock formed in the dusk side is weak and disappears at the intermediate position reflecting the azimuthally flowing nature of the Jovian disc wind.
A unique model of the Jovian low latitude magnetospheric boundary structure which consists of the double shock (bow shock and internal shock) and the double magnetopause (magnetopause and internal magnetopause), has been proposed. The data obtained by the in-situ observations suggest the existence of the theoretically proposed boundary structure. This coincidence suggests a indirect confirmation of the existence of the Jovian disc wind which is proposed on the theoretical base.

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Methodical examination of dynamic spectra of Pc3-4 geomagnetic pulsation activity recorded over 25 months at an L=2.1 ground station shows that activity can be sorted into distinct phenomenological classes based on the spectral structure of the signal. The most common features observed were sustained, relatively narrowband signals exhibiting periodic variation in amplitude, comprising oscillations at two or more nearby frequencies. Short duration wavepackets of sinusoidal oscillations were also found to be very common structures. Often, intervals of irregular, quite broadband oscillations in the Pc3-4 range were observed, with durations of a few minutes to several hours. Frequency structured activity comprising multiple spectral components, or pulsations whose frequency changed suddenly or smoothly, were observed on average every second day. Finally, intervals of sustained, sinusoidal monochromatic oscillations were observed on infrequent occasions. It is unlikely that all these diverse spectral features result solely from the dynamic response of the magnetosphere to varying conditions of geomagnetic agitation. It would seem that the respective excitation and generation mechanisms play at least some part in determining the spectral structure of pulsation signals recorded on the ground. Consequently, careful interpretation of dynamic spectra can assist in understanding both the mechanisms by which the pulsations are generated, and the temporal evolution of these generation processes with the level of geomagnetic agitation. It is concluded that there are good reasons to make a systematic study of dynamic spectra an integral part of any comprehensive analysis of geomagnetic pulsation phenomena.

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A magnetic balance operating between -196°C and 800°C with magnetic fields up to 1.2MAm^-1 is described. The typical noise level of the instrument corresponds to a sample dipole moment of 1.6×10^-7 Am² (the moment of 1.7μg of magnetite magnetized to saturation at room temperature or about 200μg of typical basaltic rock). Small samples may be used which leads to consistency between the calibration figure for both ferrimagnetic and paramagnetic minerals coexisting in the same sample and also allows rapid temperature change. An important feature is a programmable temperature-time regime. Above room temperature heating rates between 2°/min and 100°/min can be selected, and the influence that heating rate can have on the form of the thermomagnetic curve is demonstrated.
The magnetic balance operating in high field is the principal instrument for Curie point temperature determination. However, the balance has much wider application than this one task. The balance is a powerful tool in magnetochemistry or in monitoring temperature-induced structural transformations. We present here results which, for the first time, show the temperature dependence of the inversion process by which the cation-deficient magnetic minerals in submarine basalts transform to other magnetic phases. It may be that inversion proceeds at a slow rate under submarine conditions. Such inversion, which is accompanied by a change in saturation magnetization and grain size, will inevitably affect the intensity of remanent magnetization and magnetic susceptibility of the submarine crust.

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A two-dipole model is used to simulate the behaviour of the geomagnetic field during two successive polarity transitions (R→N followed by N→R) reported by VALET and LAJ (1981) from a 6Ma old marine clay sequence in western Crete. The model consists of an axial geocentric dipole and an offset minor dipole located at the northern core-mantle boundary. During the transitions the geocentric dipole decays exponentially through zero and then recovers its opposite polarity state. The axial offset dipole has two components: a time-varying and a standing one. In the middle part of the reversal process the standing component controls the transitional field and is responsible for the steep negative inclinations observed in both transitions.
The advantage of the two-dipole model compared to some other transition models is that it is capable of describing not only the inclination and intensity transitions but also the properties of the field during intervals of stable polarity, including the departure of inclinations from the axial geocentric dipole value, the symmetry of the older (R→N) reversal and the asymmetry of the younger (N→R) reversal. In a global perspective the model predicts that the shapes of intensity and inclination curves during the transitions depend on the observer's site latitude and that the onset and termination parts of these curves may differ. Because the model is axial it cannot produce the observed declination transitions. In spite of this the model produces VGP-latitude vs. stratigraphic height curves and field intensity vs. VGP-latitude curves consistent with results derived from Hoffman's flooding model.

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