The fields for quiet days of 1976 and 1977 are studied for a line of observatories established near 76°E longitude in the Northern Hemisphere. Using a special spherical harmonic analysis (SHA) technique to separate the external and internal parts of the observed field changes when the geomagnetic activity index Kp had low values, we demonstrate that a selection of SHA polynomials with (n - m) ≥ 1 serves to isolate the polar region field contributions. The equivalent external current representation of the polar fields (sometimes called Sq^P) show two vortices separated by the day-night hemisphere boundary. When plotted in local time, the nighttime current patterns are usually observed to change positions to earlier locations when the IMF sector structure varied from the Toward (IMF B_y negative) to the Away (IMF B_y positive) direction (with respect to the Sun) of the arriving solar wind field at the magnetospheric boundary. The addition of these changing polar current patterns with the more stable lower-latitude Sq (solar quiet-time) dynamo currents probably accounts for the previously reported sector effects in the Sq. The technique of selective separation of polynomials shows that the Sq could be adequately described by the SHA polynomial terms having (n - m) < 2 and that there persisted a small mid-latitude vortex of SHA polynomial (n - m) = 1 currents in winter. The polar region activity and the Southern Hemisphere Sq vortex extension into the Northern Hemisphere had overshadowed the wintertime expression of the low amplitude Sq vortex in the full-field daily variation records.

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The contribution of the excited state species 0(¹S) to the production of 0(¹D) in the nocturnal F-region is investigated here utilizing rocketborne electron density and photometric (557.7 nm and 630 nm) airglow data obtained over Natal (geogr. 5.8°S, 35.2°W), in Brazil, on October 31, 1986. Even though this contribution is rather small it is observed to remarkably vary with height. In the bottomside ionosphere it varies from 1.15% at 190 km to 6.85% at 265 km. It is suggested here that such rapid height variation in the contribution at the bottomside ionosphere is associated with a positive height gradient of the O₂⁺ population at higher vibrational levels (ν = 1 and 2). Such hypothesis is consistent with the fact that in the individual neutral dissociative state of the ¹Σ_u⁺ symmetry, which is the only source channel for the O(¹S), the rate of production of O(¹D) increases with ν. The contribution of the cascading process to the OI 630 nm airglow, which is generally assumed to be negligible, is found here to be about 5.1% of the total OI 630 nm airglow intensity.

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The J = 6_{1, 5} - 6_{0, 6} (110.8359 GHz) line of mesospheric and stratospheric ozone has been observed by employing a newly developed microwave ozone sensor equipped with a Nb SIS mixer receiver in a temporal manner. The SIS mixer has a receiver noise of 34 K (SSB) and the spectrometer covers >60 MHz bandwidth with a frequency resolution of 35 kHz. Altitude profiles of ozone concentration retrieved from observed line profiles are compared with those in Keating et al. (1990) and in Parrish et al. (1992) for inter-comparison and obtained agreement with an accuracy of about 10% in the altitude range between 40 and 50 km. From these observations, the following are concluded. (1) Time profiles of relative variations of mesospheric O₃ concentration at dawn and dusk are obtained with a good time resolution. (2) Diurnal variations of ozone mixing ratio at various altitudes from 36 km through 76 km appear qualitatively in agreement with theoretical calculations and earlier observations except nighttime variations near the top of the mesosphere. (3) Ozone mixing ratio above 70 km shows nighttime variations variable from day to day with an amplitude of about 20% of the midnight values.

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We have studied the non-steady evolution of both gas and solid grains in the convective solar nebula by using accretion disk model. Time-dependent processes considered are the accretion from the outer boundary of the nebula, the collisional growth of grains, the sublimation/recondensation of solid ice. The calculations show that the grain growth weakens the convection, and therefore the laminar nebula is left. The remaining nebula has about 0.05 solar mass with the lifetime of about 107 years. This remnant mass shows weak dependences on the efficiency factor a in the turbulent viscosity and the accretion rate. The spatial distribution of the remnant gas is determined by the size of grains because they grow to the size of mm-cm. This remnant mass is smaller than that of Ruden and Pollack (1991) because of the heatings besides the dissipation which decreases at the final stage. Thus the grains and the heating sources are the keys to guess the remaining mass and its distribution, or in other words, the initial condition of planetary accumulation.

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Based on the geomagnetic data from repeat stations and observatories, the spherical cap harmonic model of the geomagnetic field over East Asia was derived. The pole of the spherical cap is at 45°N and 105°E and the half-angle of the spherical cap is 45°. The maximum index of the spherical cap harmonic analysis is 12, giving the minimum wavelength of 1635 km. The root mean square deviation values of the spherical cap harmonic model are 122.8 (north component), 103.4 (east component) and 128.0 nT (vertical component). The geomagnetic charts of East Asia were drawn at epoch 1980.0 from the spherical cap harmonic model. Furthermore, the deviation of the spherical cap harmonic model from DGRF 1980 was calculated, and the corresponding contour charts were drawn.

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Soufrière volcano is an andesite explosive volcano located in Guadeloupe in the lesser Antilles arc. Since the last magmatic eruption dated 1440 ± 40 AD several violent phreatic eruptions have occurred. The two last 1956 and 1976-1977 phreatic/phreato magmatic eruptions were preceded by several decades of quietness. During these quiet periods, hydrothermalization and argillization are expanding due to high tropical rainfalls (10 to 12 m per year). Sealing of fractures yields more and more difficult the release of thermal stresses developed by the magmatic body supposed to be at 6 km depth. Overpressures are increasing in confined superficial water tables. Renew of seismic activity started in May 1992. About 1400 earthquakes were recorded between May and December 1992. The onset of activity was preceded, one year before, by a slight increase of vapor emission inside South crater located on Soufriére dome at the upper end of August 30, 1976 fault, by the reactivation of the small Tarade hot spring dried up since the 1976-1977 eruption, and by the appearance of a new, low flow rate, hot spring called Pas du Roy (about 30°C). A Self Potential (S.P.) survey has been performed in July 1992 on Soufrière massif. The S.P. anomalies evidence structural heterogeneities and ground waters flowing within the massif. A large, smooth, positive S.P. anomaly, composed of two localized and pronounced anomalous zones, is spreading on the south-west-south-east sector of the dome basis. The larger anomalous zone is located on Morne Mitan in the axis of the regional Ty and August, 30, 1976 faults. This zone is extending along the contact zone between Soufrière dome and Carmichaël cone. The 1992 survey is compared with 1987 survey. Soufrière dome is now submitted to a ring of positive S.P. anomalies which are lying along the inner part of Amic crater. The positive anomalous zone located on Morne Mitan has developed since 1987. The second anomalous zone, located on the south-west part of the dome, was not observed in 1987. The amplitude reaches 200 mV. The S.P. mapping points out that warm ground water beneath the south part of the volcano summit, along clayey beds, could generate the collapse of the south-west-south-east sector of Soufrière dome.

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The effect of source field geometry on the response function (ΔZ/ΔH), used in geomagnetic depth sounding to decipher lateral conductivity distribution within the earth is highlighted with the help of contour plots of ΔZ/ΔH ratios for day and nighttime short-period fluctuations recorded through a large-scale magnetometer array operated in the equatorial region of southern India. The representation of the difference between day (non-uniform) and night (uniform) time ratios in terms of the spatial derivatives of source field suggests that the reduction in daytime ΔZ/ΔH ratios at stations close to the periphery of the electrojet is due to the mutual balance of external and internal parts in ΔZ. The reduction in daytime ΔZ/ΔH ratios near the center of electrojet axis is interpreted to indicate the weakening of the intensity of induced currents due to the presence of second and higher order spatial derivatives in the non-uniform source field.

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