K. B. Serafimov

A note on the use of absorption measurements for improving the IRI electron density distribution in the lower ionosphere

Abstract Advantages and disadvantages of radio measurements by ground based techniques are discussed with a view to improve the IRI. In particular, these techniques allow the diurnal, seasonal and solar cycle variations of the D-region to be continuously followed. Also, the spatial variations might be established with a network of stations measuring radio wave absorption on several frequencies. In case of strong events, it is important to follow their development in space and time. It seems that absorption measurements alone do not allow the determination of the electron density profile unambiguously. It is, however, suggested that the addition of vertical soundings (with profile computation) potentially combined with rocket and balloon borne pressure determinations might produce some indications about how a certain part, at least, of such data might be used to check/improve the description of D-region variations in time and space.

The improvement of IRI profiles of O2+, NO+ and O+ by means of airglow measurements

Abstract Methods were suggested in /1,2,3/ to find the maximum electron density N m F (or N m F2) and the) corresponding height h m F (h m F2) in the ionosphere through a combination of measurements on two airglow lines: the UV oxygen line at λ135.6 nm and the red oxygen line near λ630 nm.

Proposal for the improvement of the electron density profile of the F-region

Based on the empirical description of daytime mid-latitude hmF2, an appropriate expression for the global normalized value of the vertical velocity (W) for the F-region electron transport is suggested. Using combined profiles of electron concentration (N) by satellite and ground-based techniques, the heights he1 and he2 at which the gradient ∂N∂h attains maximum are obtained. An expression is developed to combine Nm with D0, the initial diffusion coefficient and β0 the maximum attachment coefficient. The parameters D0 and β0, as well as the constants A0 and A1 appearing in the IRI-79 topside description are determined using he1 and he2. The values of A0 and A1 which fit the measurements from a variety of techniques such as ionoside, A2 absorption, satellite beacon, airglow measurements and other ground-based techniques are suggested.

Latitudinal asymmetry in electron and ion density distribution in southern and northern hemispheres

Abstract With data of satellite INTERCOSMOS-BULGARIA-1300 northern and corresponding southern hemisphere plasma densities have been compared. Southern densities are greater in the −90 to −180 and +30 to +120° ranges. The opposite is true for −60 to +30°. No asymmetry has been observed during daytime. These results are explained by the variations of the magnetic declination.

Thermospheric modelling based on satellite and ground-based measurements

Abstract Methods, analytical expressions, and procedures are suggested for combining TEC (total electron content) calculations (based on Faraday rotation or differential-Dopper measurements), ground-based ionosende measurements, and the intensity of airglow emissions to study the upper atmosphere. For example, we have considered the possibility of determining ionized and neutral parameters at thermospheric altitudes by combining ground-based measurements of N e (h), TEC, and the airglow intensities at 6300 A, 5200 A, 7774 A, and of other such lines. These combined data can be supplemented by in situ satellite measurements and EUV airglow observations at 1304 A, 1356 A, etc. This process will provide a data base for thermospheric modelling and for comparison with existing models.

Thermospheric heating at high latitudes as observed from Intercosmos-Bulgaria-1300 and Dynamics Explorer-B

This paper reports the results of the first direct comparison of near simultaneous measurements obtained by the INTERCOSMOS-BULGARIA-l300 and the DYNAMICS EXPLORER-B satellites. The ICB—l300 is in a near circular orbit at a mean height of about 850 km. The DE-B satellite in an elliptical orbit is sometimes directly below the ICB-1300 satellite providing an opportunity to investigate the response of the thermosphere to particle fluxes from the magnetosphere. Energy fluxes in the range 0.2 — 15 key are obtained from an energetic particle analyzer on board the ICB-1300 satellite. The thermospheric composition and density are obtained by a neutral gas mass spectrometer (NACS) on the DE-B satellite. During the period 20 August — 20 November, 1981, observations show that the times and locations of maxima in magnetospheric energy deposition coincide with regions of maximum thermospheric upwelling characterized by composition changes.

Bottomside N(h) profiles over Vietnam and their comparison with IRI

Over 70 ionograms were selected from the ground-based ionosonde in Hanoi, Vietnam at times when the AE-E satellite passed above the station. N(h) profiles were calculated from ionograms and thus compared with the IRI model and local AE-E ion densities. For the purpose of the presentation, 15 profiles were selected to cover all seasons and local times. The comparison shows that the observed daytime N(h) profiles have significantly higher gradients below the F2 peak density while at night the observed and the IRI profiles almost coincide. The difference is more pronounced in summer than in equinox. Wintertime comparisons are quite limited and do not lead to reliable conclusions. NmF2 values taken from the CCIR programme are compared with those observed. The comparison shows that the deviations are not so large.

Optical investigations of magnetospheric-ionospheric coupling by using data from the Intercosmos-19 satellite

Abstract In this paper we present the main parameters measured by the ionospheric observatory “Intercosmos-19”. In particular data from the visible electrophotometer EMO-1 are shown. Some preliminary results related mainly to the behaviour and distribution of the red line emission at higher latitudes are also given.

Stratifications in the E-region and their relations with the sporadic Es-layer and the neighbouring ionospheric parts under different time and space conditions

The stratifications in the E-layer observed with normal and special ionograms as well as their daytime, seasonal and cyclic variations are analysed. Their inter-relations in neighbouring ionosoundings are determined. The interactions between the E-layer stratifications and the development of the normal E-2 Layer are shown, as well as the stratified formations in the intermediate E-F region. The mutual relations between the different stratified formations in the E-region, the sporadic Es layer and the neighbouring ionization in the F- and D-regions are established and analysed.

An IRI-based improvement of the electron density distribution in the lower ionosphere

Abstract Methods for combined probing of the lower ionosphere are suggested and an approach is given for finding some basic parameters.