Great diversity of the ionospheric phenomena leads to a variety of irregularity types with spatial size from many thousands of kilometers to few centimeters and lifetimes from days to fractions of second. Since the ionosphere strongly influences the propagation of radio waves, signal distortions caused by these irregularities affect short-wave transmissions on Earth, transionospheric satellite communications and navigation. In this work the solar wind and the equatorial ionosphere parameters, Kp, Dst, AU, AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the space weather effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict scintillations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind-magnetosphere-ionosphere during magnetic storms have progressed greatly. We have examined scintillation relation to magnetospheric and ionospheric currents and show that the factor, which presents during magnetic storms to fully inhibit scintillation, is the positive Bz-component of the IMF. During the positive Bz IMF F layer cannot raise altitude where scintillations are formed. The auroral indices and Kp do better for the prediction of the ionospheric scintillations at the equator. The interplanetary magnetic field data and models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, f₀F2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind. Taking into account the time delay between the solar wind and the ionosphere phenomena, the relationship between the solar wind and the ionosphere parameters can be used for predicting of scintillations.

The main ionospheric trough can be formed as result of horizontal convection and field-aligned plasma transport, changes in the electric and magnetic fields, precipitation of electrons, interaction of ionospheric plasma with neutral components and recombination and ionisation processes occurring in the ionosphere and inner magnetosphere. Recently the position of the minimum, and poleward and equatorward edges of the main ionospheric trough has been determined by a hybrid method based on wave diagnostics across the whole frequency band, together with electron and density temperature measurements. For terrestrial HF systems, the electron density depletion in the trough region reduces the maximum frequency that can be reflected by the ionosphere along the great circle (GC) path. The gradients in electron density associated with the trough walls and embedded ionospheric irregularities often result in propagation in which the signal path is well displaced from the GC direction with directions of arrival (DOA) at the receiver offset by up to 100°. Deviations from the GC direction impact not only on radiolocation systems for which estimates of a transmitter location are obtained by triangulation from a number of receiving sites, but also on any radio communications system in which directional antennas are employed. In this paper, in order to determine the mechanisms that are responsible for the off GC behaviour described above, HF signals propagating along the Uppsala-Leicester path are examined in the context of DEMETER observations of electron density structure and particle precipitation in the ionospheric trough region for a number of case studies.