[en] The structure of the auroral oval with aurorae is discussed. Coordinates of pole and equatorial oval boundary of discrete aurorae and equatorial boundary of diffuse aurorae for different levels of magnetic activity and different hours of local geomagnetic time are given. 1 fig., 1 tab

No abstract available

[en] Complete text of publication follows. The geomagnetic data from off equatorial and equatorial stations Alibag (18.64 deg N, 72.87 deg E) and Trivandrum (8.48 deg N, 76.94 deg E) in Indian zone during 1995 and 1996 are used for the calculation of strength of Equatorial electrojet. The EEJ were categorized according to their strength and direction Viz Normal electrojet (NEJ, When the maximum strength is 50 nT), Abnormal electrojet (AEJ when maximum strength is less than 10 nT) and counter electrojet (CEJ the reversal of EEJ). Correlation between Del Y and EEJ was investigated on days which were characterised by SEJ, NEJ, and CEJ events. The hour to hour variation shows that anticorrelation is observed between Del Y and EEJ strength of all categories. However this behavior was not present on some days. The factors responsible for this variation are analyzed. It is observed that the strength of Sq and EEJ current system play major role in this mechanism. The shifting of Sq system pole wards on NEJ days comparing with AEJ days.

No abstract available

[en] The causative atmospherics of very-low-latitude whistlers whose ionospheric exit regions have previously been determined at geomagnetic latitudes, 10-13 deg, are located in order to aid the understanding of the magnetospheric propagation mechanism of very-low-latitude whistlers. It is found that the causative atmospherics of very-low-latitude whistlers are very widely distributed in a range from 500 to 2500 km from the conjugate point of whistler ionospheric exit region previously determined. This fact lends further support to a previous implication that magnetospheric preferred paths supporting field-aligned propagation are extremely rare in occurrence and that there has existed a preferred and stable magnetospheric path in a very restricted location on the day of high whistler activity. 17 refs

No abstract available

[en] A static 3-dimensional model of the polar ionosphere is considered. The spatial distribution of Ne electrons appearing in the ionosphere being passed by auroral electron flows is calculated. The problem is solved in the stationary approximation with the use of ion formation rates calculated from the results obtained by the ISIS-2 satellite. The static model gives detailed information on height profiles of Ne electrons; the accuracy, however, depends on geomagnetic coordinates

[en] A moving coordinate system for a dipole magnetic field, in which reversible variations of magnetic moment for the range of obvious violations of adiabatic conditions are absent, and the description of magnetic moment violations is relatively simple, is considered. Constructing of a coordinate system, features of the central trajectory, determining its motion, the application range, the main application field and consequences are discussed. 11 refs.; 3 figs

[en] Using MLT-UT diagrams development of substorms in the period of 17, 18 and 19 of March, 1978 is investigated in detail. MLT-UT diagrams of AE index are shown to give avidence planetary peculiarities of development of auroral electrojets. On their bases any geomagnetic activity period may be divided into separate substorms and it is possible to determine electrojet maximum position

[en] A study of the secular variation in the geomagnetic elements H, Z, F and D at Colaba (Bombay)-Alibag for the period 1848-1973, has been made. Fifth degree polynomials are fitted to the data of annual mean values of H, Z and F, and third degree to D, and the residuals discussed. The trends are also examined at the six Indian observatories using the data for 1960-1974. The increasing trend of Z at Alibag is found to decrease from about 1937, while that of H and F from 1965 at 20-30 nT/year, it being of the same order at Sabhawala and Hyderabad but smaller at the equatorial stations, particularly for Z component. The westward annual change in D swings eastward again around 1965 at all the Indian stations. This reversal of the secular variation trend in India after 1965 emerges as an important regional feature connected with a southward migration of the dip equator in India from 1968. The secular change in D at Alibag (+0.4'/year) is somewhat anomalous in the sense that it is reduced as compared to Hyderabad and other stations (+1.6'/year), probably due to the local magnetic anomaly of the Deccan lavas, and calls for detailed investigations. (auth.)