arXiv subjects

A. P. Potekhin

Publications and source records attributed to A. P. Potekhin.

4 recordsLinked to original sources

arXiv2016

SuperDARN scalar radar equations

The quadratic scalar radar equations are obtained for SuperDARN radars that are suitable for the analysis and interpretation of experimental data. The paper is based on a unified approach to the obtaining radar equations for the monostatic and bistatic sounding with use of hamiltonian optics and ray representation of scalar Green's function and without taking into account the polarization effects. The radar equation obtained is the sum of several terms corresponding to the propagation and scattering over the different kinds of trajectories, depending on their smoothness and the possibility of reflection from the ionosphere. It is shown that the monostatic sounding in the media with significant refraction, unlike the case of refraction-free media, should be analyzed as a combination of monostatic and bistatic scattering. This leads to strong dependence of scattering amplitude on background ionospheric density due to focusing mechanism and appearance of new (bistatic) areas of effective scattering with significant distortion of the scattered signal spectrum. Selective properties of the scattering also have been demonstrated.

physics.geo-ph↗

arXiv2010

The influence of electron density gradient direction on gradient-drift instabilities in the E-layer of the ionosphere

We show that the dispersion relation for gradient-drift and Farley-Buneman instabilities within the approximation of the two-fluid MHD should contain the terms which are traditionally supposed to be small. These terms are caused by taking into account divergence of particles velocity and electron density gradient along the magnetic field direction. It is shown that at heights below 115km the solution of the dispersion relation transforms into standard one, except the situations, when the electron density gradient is parallel to magnetic field or wave-vector. In these cases the traditionally neglected summands to the growth rate of the irregularities becomes significant. The additional terms depend on relative directions of electron density gradient, magnetic field and mean velocities. This leads to the different instability growth conditions at equatorial and high-latitude regions of the ionosphere. The obtained results do not contradict with the experimental data.

physics.plasm-ph↗

arXiv2002

A case study of the mid-latitude GPS performance at nighttime during the magnetic storm of July 15, 2000

Using the geomagnetic storm of July 15, 2000 as an example, we investigated the dependence of GPS navigation system performance on the nightside at mid-latitudes on the level of geomagnetic disturbance. The investigation was based on the data from the global GPS system available through the Internet. It was shown that the number of GPS phase slips increases with the increasing level of disturbance and that there is a good correlation between the rate of Dst-variation and the frequency of slips. It was further shown that the relative frequency of slips has also a clearly pronounced aspect dependence. Phase slips of the GPS signal can be caused by the scattering from small-scale irregularities of the ionospheric E-layer. Phase slip characteristics are indicative of Farley-Buneman instabilities as a plausible physical mechanism that is responsible for the formation of geomagnetic field-aligned irregularities. Using simultaneous measurements of backscatter signal characteristics from the Irkutsk incoherent scatter radar and existing models for such irregularities, we estimated the order of magnitude of the expected phase fluctuations of the GPS signal at a few degrees.

physics.geo-ph↗

arXiv2001

Radar equations in the problem of radio wave backscattering during bistatic soundings

This paper outlines a method of obtaining the relation between the singly scattered signal and the Fourier-spectrum of medium dielectric permititvity fluctuations, with due regard for the fact that the scattering volume is determined by antenna patterns and is not small. On the basis of this equation we obtained the radar equation relating the scattered signal spectrum to the spatial spectrum of fluctuations. Also, a statistical radar equation is obtained, which relates the mean statistical power of the scattered signal to the spectral density of the dielectric permitivity fluctuations without a classical approximation of the smallness of the irregularities spatial correlation radius. The work deals with the bistatic sounding case, when the exact forward and exact backward scattering are absent, and sounding signal have sufficiently norrow spectral band for scattered volume to change slowly on ranges of Fresnel radius order. The statistical radar equations obtained differs from the classical ones in the presence the coherent structures with big correlation radii, and so the received signal spectrum can differ from intrinsic spectrum of irregularities.

physics.ao-ph↗