Variations Of Ionospheric Parameters Research Articles

Ground-based observations of the March 26, 1976 magnetospheric storm

Abstract An analysis has been made from a geophysical complex operating during magnetospheric storm, with the purpose to study ground level manifestations of such disturbances and of the recovery process of prestorm conditions. The maps of electrojets were constructed with data from the magnetometer chains located on the Yakutsk (130° E) and Norilsk (90° E) meridians. The analysis of variations of ionospheric parameters were conducted from three ionospheric stations of Yakutsk (Tixie, Zhigansk, and Yakutsk), and two of Norilsk (Dixon and Norilsk) meridians and of Arkhangelsk (40° E). The conclusions are made that strong disturbances in the magnetic field are governed by universal time and observed over an extensive range of longitudes, week disturbances are operated by local time and latitude of observation.

Lower ionosphere response to conductivity variations of the near-earth atmosphere

Abstract Anomalous changes in VLF amplitudes and phases observed on propagation paths crossing either nuclear power station areas with an increased level of radiation or seismoactive regions at times preceding an earthquake have been analyzed. A comparison of the data related to these different situations gives grounds to suggest a physical cause which is common to both cases, namely the increased conductivity of the lower atmosphere. A lithosphere-ionosphere interaction model is put forward, involving atmospheric vertical conduction electric currents, the variations of which can change the electric potential of the lower ionosphere. The ionospheric parameter variations have been estimated, compared with the gathered data, and both quantitative and qualitative agreement found.

Experimental investigation of the coupling process in the middle atmosphere/lower thermosphere/ionosphere system

The paper briefly reviews some investigations realized mainly in Southern Spain of possible coupling between middle atmosphere, lower thermosphere and ionosphere. It draws attention to abnormal circulation changes in the winter stratosphere, detected through variations of D-region ionospheric radiowave absorption; the response of the lower ionosphere to the stratospheric warmings; quasi-periodic fluctuations in ionospheric absorption in relation to planetary wave activity in the stratosphere; the statistically significant correlations between variations of total ozone content considered as a parameter of the stratospheric changes; and radio waves absorption as an indicator of the electron density in the lower ionosphere. There is some difference in the behaviour of the lower ionosphere in relation to meteorological parameters in Southern Spain and Central and East Europe, and this is discussed as partly due to latitudinal variations of ionospheric parameters and to longitudinal inhomogeneity of lower atmosphere processes.

Variations in ionospheric parameters during periods of minimum and maximum solar activity

Ionospheric investigations in Ukraine are being carried out with uniquely developed incoherent scatter radars. Data on the variations in the electron density and the electron and ion temperatures during periods of low (1994) and high (1989 - 1990) solar activity are presented. The F-layer peak height ranges from 450 at night to 240 km in the daytime; the electron density maximum varies approximately from over a cycle of solar activity throughout the winter period. The electron temperature has a maximum afternoon value as the solar activity is high in summer. In the periods of magnetic disturbances, a drop in is most frequently observed. In winter, the influence of the sunrise and sunset at the magnetic conjugate point is also observed. An increase in electron temperature, a drop in electron density, and the displacement of the heated region along the magnetic field lines are clearly seen in the ionosphere irradiated by high-power, HF radiation. Longitudinal effects in the ionospheric behaviour were observed in simultaneous measurements in Kharkiv and Millstone Hill (USA).

The sondrestrom radar and accompanying ground-based instrumentation

The Sondrestrom radar facility, funded by the NSF Upper Atmospheric Facilities Program, is operated and managed by SRI International. The facility is located on the west coast of Greenland, just north of the Arctic Circle, near 75 deg invariant magnetic latitude. The principal instrument at the facility is the incoherent scatter radar. The incoherent scatter technique allows the direct measurement of ionospheric electron number density, ion velocity, and electron and ion temperature along the radar beam. Because the radar antenna is fully steerable these parameters can be determined as functions of horizontal distance and altitude. Additional ionospheric quantities can be derived using these measured parameters. As part of the ISTP mission, the radar will measure the spatial (horizontal and altitudinal) and temporal variations of ionospheric parameters including electron density, large scale electric field. conductivity, currents, and energy input. Repetitive measurements define variations of parameters with local time, as well.

Morphology of the D-region in northern Scandinavia during the campaigns MAC/SINE and MAC/EPSILON in 1987

The morphology of the lower ionosphere was examined by the riometer and ionosonde networks in Scandinavia during the campaigns MAC/SINE and MAC/EPSILON. The campaigns were carried out during 1987 when the solar activity was low. The minimum sunspol number 14 was observed in 1986. The sunspot number was already increasing during the year 1987, while the Ap-value and riometer absorption were still decreasing. During the campaign MAC/SINE the rockets were launched during quiet periods, and during the campaign MAC/EPSILON during more disturbed periods. The variations in ionospheric parameters, ionospheric absorption and foF2 are presented for the campaign periods. Some interesting events are pointed out.

Meteorological effects in the variations of ionospheric parameters—I. The lower thermosphere

The influence of the troposphere and stratosphere on variations of ionospheric D-region parameters are discussed. It is found that variations of the minimum observable ionosonde frequency ( f min ) and horizontal winds are closely related to temperature and pressure fields in the lower atmosphere. Experimental data for the Central Asian and East Siberian U.S.S.R. regions have been used.

Some Effects of Nuclear Explosions on the Ionosphere

Examination of spread-F conditions at Brisbane and other stations adjacent to the Pacific area, together with an investigation of h'F2 and foF2 changes at the time, suggest that three disturbances propagated from the site of the nuclear explosion at Johnston I. on August 1, 1958. Somewhat similar variations of ionospheric parameters occurred after the explosion on the same site on August 12, 1958. The average speeds of these disturbances were 1666, 647, and 333 m/s.