[en] Complex experiment covering satellite radioscopy and vertical probing of ionosphere is carried out to obtain a comprehensive range of parameters characterizing average-scale moving ionosphere disturbances

[en] A three-dimensional ray-tracing analysis is employed to calculate ray paths through a model ionosphere which itself is perturbed by the passage of horizontally moving wavelike disturbance. A knowledge of various parameters (e.g. phase and group paths, angle of arrival, Doppler frequency shift) for ray paths connecting a central transmitter with spaced receivers permits an evaluation of several spaced-station techniques for measuring horizontal phase velocities of travelling ionospheric disturbances (TIDs). It is shown that in experiments with transmitter-receiver spacings of less than 150 km, reliable velocity estimates may be expected, even though the assumption of a horizontally stratified ionosphere which is common to all methods is strictly invalid. (author)

[en] Complete text of publication follows. First discovered by Chung Park in 1973, the plasmasphere within the new plasmaspheric boundary layer during magnetic storms could undergo a noticeable decrease in density, and this depletion could represent a significant fraction of the overall losses from the plasmasphere. Several processes, such as plasma dumping to the ionosphere, have been proposed as the cause of internal plasmaspheric depletion during storm times, but finding the responsible physical mechanism remains an outstanding problem. As an effort to identify the important causes to this complicated phenomenon, this study examines a collection of critical ground and satellite observations, including the mass density inferred from field line resonance sounding, the charge density deduced from whistler traces, ionosonde data, and the RPI observations from the IMAGE satellite. We find that the plasmasphere within the new plasmaspheric boundary layer does not necessarily decrease in all magnetic storms. An enhancement in plasmaspheric density can sometimes be found. The increase or decrease in plasmaspheric density echoes the change in ionospheric content during the storm event. Our results suggest that, during magnetic storms, the related ionospheric storms may play a major role controlling the internal plasmaspheric content.

No abstract available

[en] The statistical features of field-aligned currents include the following: (1) The large-scale regions of field-aligned currents determined previously persist during all phases of substorm activity. Namely, region 1 located near the poleward boundary of the field-aligned current region and region 2 located near the equatorward boundary. Field-aligned currents flow into region 1 on the morning side and away from region 1 on the evening side. The current flow in region 2 is reversed to region 1 at any given local time except in the Harang discontinuity region (-- 2000 - 2400 MLT) where the flow patterns are more complicated. (2) During active periods, the average latitude width of regions 1 and 2 increases by 20% to 30% and the centers of these regions shift equatorward by 2⁰ to 3⁰ with respect to the quiet time values. (3) The current density is statistically larger in region 1 than in region 2 at all local times except during active periods and in the midnight to morning local time sector. (4) During relatively quiet conditions, the largest field-aligned current densities occur in two areas of region 1 near noon (near -- 1030 MLT and -- 1300 MLT) with an average value of -- 1.6 μamp/m². During active periods, the regions of peak current density shift toward the nightside (the region near 1030 MLT shifts to --0730 MLT, and the region near 1300 MLT shifts to -- 1430 MLT) and the average current density increases to -- 2.2 μamp/m². (5) The average total amount of field-aligned current flowing into the ionosphere always equals the current flow away from the ionosphere during a wide range of quiet and disturbed conditions. (6) A three-region pattern of field-aligned current flow persists in the Harang discontinuity region (-- 2000 - 2400 MLT) during undisturbed and disturbed periods when the westward auroral electrojet does not intrude into this sector. (J.P.N.)

[en] Analysis of the experimental data on the ionosphere probing using various methods in different regions proves the hypothesis about the occurrence of the isolated large-scale moving disturbances of the electron density with 500-3000 km dimensions within 200-2000 km high-altitude range. Disturbances are of nonlinear nature and affect essentially various range radio-signals

[en] Published in summary form only

[en] The ionospheric disturbances around Japan associated with the severe magnetic storm on July 14-16, 1982 were investigated using ionospheric total electron content (Nsub(t)) data obtained by the ETS-II beacon experiment and F-region data obtained by the soundings at the latitude chain of the ionospheric stations situated nearly along 135 ⁰E. The most remarkable storm effects were the negative disturbances, which are common at mid-latitudes in summer. The negative disturbances comprise decreases in Nsub(t) and peak electron density (Nsub(m)) and a marked increase in slab thickness. In addition, the following interesting events were observed during this storm: (1) sharp decreases in Nsub(t) and Nsub(m) occurred almost simultaneously in the regions from mid-latitudes to the equatorial latitude within a few hours after the storm sudden commencement (SSC), (2) some positive disturbances in the F-region appeared during the last phase of the storm, which were prominent at mid-latitudes during the night and at low-latitudes in the afternoon, and (3) a medium-scale traveling ionospheric distubance (TID) with a nearly north to south direction of propagation was observed as wavelike fluctuations of Nsub(t). (author)

No abstract available

[en] The topside ionograms over Japan were secured at Kashima by telemetry receptions of more than ten ISIS-2 passes during geomagnetic storms successively occurring from June to September 1982. The analyses of the changes in the structure of the topside ionosphere under storm time condition are concentrated on the ISIS-2 sounder data received around two severe events which commenced at 16 h 17 mUT July 13 and 22 h 48 mUT September 5, 1982. In the July event the nighttime ionosphere in the initial phase exhibited negative change in f₀F2 (ΔNsub(m)F2<0) and higher peak altitude (Δhsub(m)F2>0) in low and midlatitude with disordered horizontal gradient in electron density as compared with those in quiet condition. An analysis of the N(h) profiles and scale height profiles in the daytime disturbed condition shows the increase in a plasma temperature by about 15-40 percent, appreciable decrease in relative H⁺ density, [H⁺]/[O⁺] and raise in the transition height (O⁺ → H⁺). In the September event the f₀F2 changes in the daytime were not significant except in the equatorial zone. An ionospheric storm with positive disturbances is considered to have developed in the early stage of the main phase. A remarkable change in f₀F2 at equatorial latitudes was seen, accompanied with the enhancement and the depression of the equatorial anomaly. These changes in the topside ionospheric structure are discussed in association with the development phase of geomagnetic storms and the observations as previously revealed. (author)