satellite radio tomography
ionizing particles fluxes
E.S. Andreeva, M.A. Kozharin, V.E. Kunitsyn M.O. Nazarenko
Diagnostics of auroral precipitation is one of the important topics in the modern research on the ionospheric physics. The interest to this problem is drawn by the fact that precipitation, on one hand, reflects the state of the magnetospheric-ionospheric-atmospheric coupling and is an important element of fundamental description of the medium. On the other hand, the effects caused by precipitation play an important part in a number of practical applications, e.g. those associated with electromagnetic propagation. Particle precipitation causes redistribution of the electrical currents, various optical and UV phenomena, and variations in the ionospheric parameters (electron density, electron and ion temperature, etc.) Precipitation can affect large-scale distribution of the ionospheric plasma and modulate local ionospheric plasma structures. Being a nonlinear phenomenon by its nature, particle precipitation can generate various wave-like processes in the ionosphere.
The studies addressing the effects of precipitation, their interrelation, and linkage between their parameters with the characteristics of the precipitating particles are important field in the modern research into the physics of the near-Earth interactions. One of the directions of this research is investigation of the interrelation between precipitation and the distribution of electron density in the ionosphere by remote sensing and, primarily, by ionospheric radio tomography (RT). The methods of low-orbital satellite RT are suitable for reconstructing two-dimensional (2D) cross sections of electron density distribution in the ionosphere in the vertical plane above the receiving RT chain with a horizontal resolution of 20-30 km and vertical resolution of 40-50 km. The high-orbital RT is capable of reconstructing 3D spatial structure of the ionosphere with a resolution of about 100 km in the regions with nondense network of receivers.
In the paper, the RT images of the ionospheric electron concentration are compared with the structure of soft precipitation during quiet and geomagnetically disturbed periods. The data on precipitation are mainly derived from the DMSP satellite measurements. It is found that the distribution of electron density reconstructed by the RT methods is qualitatively similar to the latitudinal variations in the fluxes of precipitating electrons and ions. During the periods of geomagnetic disturbances, the patterns of electron density distributions contain multiple extrema and wavelike structures with a spatial scale of about dozens to hundreds of kilometers. These distributions qualitatively correspond to the structure of corpuscular ionization, which is found to widely vary from a few degrees to dozens of degrees.