The morphological development of an event in the conjugate post-noon auroral ovals over a period of an hour is presented. The Viking UV camera imaged the northern dayside oval with a temporal resolution of 60 or 80s while an active auroral form was observed by all-sky and keogram cameras to move through the zenith at South Pole station. Early in the event a general similarity of form and development is observed between the hemispheres but implying that the Northern Hemisphere forms are located of the order of four degrees of latitude higher, and of the order of one hour of MLT later, than IGRF calculated conjugate locations. Later in the event conjugacy is more difficult to establish. Short-lived features in the Southern Hemisphere photographs for which no Northern Hemisphere conjugate can be found imply that local acceleration processes may be important in this time sector.

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An apparent lifetime of the auroral red line (630.0nm OI) emission was investigated by using monochromatic auroral TV images obtained on July 18, 1984, at Syowa Station, Antarctica. We tried to evaluate a mean energy of the incoming electrons by using the temporal variation of the red line intensity. The observed red line intensity is compared with a synthesized variation of the auroral red line solving differential equations for chemical reactions in the auroral ionosphere as well as the deactivation of excited state oxygen atoms. The observational results showed that the red line intensity changed gradually keeping an apparent lifetime of about 35-40sec while the green line intensity changed step-wise. The lifetime found is significantly smaller than a value (about 110sec) previously used for the interpretation of 630.0nm (OI) auroral emission. The comparison showed that the observed apparent lifetime is consistent with a synthesized aurora excited by a low energy electrons with a characteristic energy of 0.2-0.5keV.

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It is shown that “having substorms” is not a necessary condition for a magnetic storm. The main phase of magnetic storms develops because of sustained, southward interplanetary magnetic field (IMF), not because of frequent occurrence of intense substorms.

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This paper deals with visual auroral data from Central Europe (φ: 53-48°N) during the years 1545 to 1715. The reality of these observations has been discussed in detail. From the observations it can be demonstrated that the 11-year-cycle in solar and auroral activity exists during this period. Table 2 gives a compilation of auroras per year; the table shows that in almost every year-before and during the Maunder Minimum-auroras have been observed in Middle Europe. Because they are indicators of solar geomagnetic activity it follows that no unusual variability in solar or geomagnetic activity is indicated.

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Width of nighttime equatorial scintillation belt is estimated, employing three years of simultaneous recordings of VHF signals at two equatorial and one temporate latitude stations in the Indian region. The latitudinal extent of the belt is found to be larger during D- and E- when compared with that in J-months. There appears to be a positive association between the width of the belt and solar activity but beyond a threshold, increase in sunspot number has not resulted in further widening of the belt. There is a suggestion that the solar control of scintillation activity is more pronounced at a station situated at a temporate latitude than that of equatorial station. These and other morphological features are discussed.

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We have compiled 3.5 million data of marine magnetic anomalies in four areas in the Northeast Pacific, Atlantic, and Southeast Indian Oceans and tried to produce an expansive database of marine magnetic anomalies. The boundaries of the study areas are 20°-60°N and 170°-105°W for the Northeast Pacific, 20°-60°N and 70°-5°W for the North Atlantic, 50°-25°S and 45°W-10°E for the South Atlantic, and 60°-30°S and 125°-145°E for the Southeast Indian Ocean. Marine magnetic anomalies were obtained from geomagnetic total intensity data using IGRF/DGRF. All the data of marine magnetic anomalies in those areas were reduced to a 5-minute regular grid using weighted average interpolation. The gridded data in the North-east Pacific and the North Atlantic provide quite remarkable resolution of magnetic anomaly lineations, fracture zones, and seamounts. Results in the South Atlantic and the Southeast Indian Ocean show a limit of the gridding procedure due to low data density. We can, however, see characteristic patterns of marine magnetic anomalies corresponding to major tectonic features in parts of the areas where the data density is comparatively high. This attempt to make a database of marine magnetic anomalies has succeeded at least in the Northeast Pacific and North Atlantic Oceans, because magnetic anomaly maps confirm that characteristic features of marine magnetic anomalies in these areas are well represented by the gridded data. We can easily compare the magnetic database with other database such as the database of topography (ETOPO5). As more cruise data are accumulated in areas which have lack of magnetic data, this magnetic database will be more useful, especially to analyze a global marine magnetic anomaly.

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Correlated enhancements of bremsstrahlung X-rays and VLF emissions were observed for about 10min at balloon altitude near Syowa Station (L=6.1), on December 14, 1985. The enhancements occurred quasi-periodically with the period of about 90s are investigated on spatial characteristics of energetic electron precipitation. A time sequence of localized X-ray images are composed. A systematic movement of the source region from geomagnetic SW to NE was found in the lowest energy channel of 22-35keV and its drift velocity was greater than 3.5km/s at X-ray generation height.

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