Microwave radiation in the upper atmosphere of the earth during strong geomagnetic disturbances

The influence of N₂ and O₂ molecules on spontaneous microwave radiation spectrum was studied over the decimeter range. This radiation appears in the D and E upper earth atmosphere layers during strong magnetic storms. It was shown to be caused by radiation transitions between medium-perturbed orbitally degenerate Rydberg atom and molecule states A** that occur without changes in the principal quantum number, δn = 0. The available experimental data were used to calculate the dependences of orbitally degenerate state populations on the density of medium and electron flux and temperature. Effective radiation bands were constructed for transitions between highly excited quasi-molecule levels A**N₂ and A**O₂. The emission spectrum was shown to be inhomogeneous and contain three frequency regions in which a noticeable decrease in the intensity of radiation occurred. The physical reason for the formation of these regions was a shift of the emission spectra of quasi-molecules containing unexcited N₂ and O₂ molecules. The frequency profiles of radiation intensity within these frequency regions were calculated as depending on the storm level. Radiation profiles were shown to noticeably change as the storm level increased, they strongly increased close to the right region edge corresponding to high transition frequencies. Nonmonotonic behavior of this profile in the middle of the lower region was observed; this was related to emission spectrum inhomogeneity. A sharp increase in radiation intensity as the magnetic storm level increased occurred in the region of frequencies situated close to the right edge of the upper region (50–100 GHz), which was most interesting for biophysical studies of the action of microwave radiation on living organisms during strong geomagnetic disturbances.     

Multiphoton resonant transitions in atomic Ba in the presence of additional strong off-resonant radiation

The multiphoton transitions in atomic Ba are experimentally studied in the presence of strong off-resonant radiation that generates additional atomic polarization in the ground state. It is demonstrated that the additionally induced polarization of the Ba atoms in the ground state leads to a higher probability of the multiphoton transitions from this state.     

Effect of NO concentration disturbances on the global distribution of ionospheric parameters during geomagnetic storms

The role of nitric oxide (NO) in the ionospheric effects during geomagnetic storm on May 1–3, 2010, is examined. The studies are performed using a global self-consistent model of the thermosphere, ionosphere and protonosphere (GSM TIP). Two versions of calculations are used: (1) based on an analytical approximation of the NO concentration and (2) self-consistent calculation of the global distribution of nitric oxide over the ionosphere. It is shown that, during a geomagnetic disturbance, the NO concentration at high latitudes shows an increase, which under the influence of the horizontal circulation of neutral gas leads to an increase in the concentration of NO at mid-latitudes ～1 day after the start of the perturbation. Simulated values of foF2 are compared to experimental data obtained at a number of Russian mid-latitude stations. It is noted that the self-consistent calculations of the NO concentration better describes the spatial-temporal behavior of ionospheric parameters during geomagnetic storms.     

Dispersion equations of low-frequency geomagnetic disturbances in the E-layer

The effect of the altitude distributions of the Hall and Pedersen conductivities on the dispersion equations of lowfrequency geomagnetic disturbances (GMD) is studied. Single-layer and two-layer models of the E-region are examined with allowance for the earth's conductivity and wave radiation into the magnetosphere. The form of the dispersion equations and the physical mechanisms of GMD propagation along the E-layer are analyzed as functions of the geomagnetic-field orientation.     

Evolution of wave disturbances in the upper ionosphere. Part II

A theoretical analysis of the vertical propagation of large-scale wave disturbances in the F region and outer ionosphere is presented. The analysis has included all the major factors influencing the dynamics of the ionospheric plasma under mid-latitude conditions. It is shown that the disturbances propagating downward in a strongly inhomogeneous medium rise in intensity up to the heights of the F₂-layer maximum and are damped then in the lower layers of the ionosphere. This mechanism can be considered a source responsible for the inhomogeneous structure of the upper ionosphere. State University, Irkutsk, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 9, pp. 1086–1092, September, 1998.     

Study of the lower ionosphere using artificial periodic irregularities

We report on the studies of the lower ionosphere with improved height resolution using artificial periodic irregularities. This method is useful for studying the irregular structure of the ionosphere. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 9, pp. 1077–1085, September, 1998.     

Monitoring of wave-like disturbances by means of oblique sounding of the ionosphere

We present the results of experimental studies of ionospheric wave-like disturbances on the basis of oblique chirp sounding data for the mid-latitude paths Cyprus-Rostov-on-Don and Inskip-Rostov-on-Don. Twenty-four-hour measurements were performed in January-May and October–November, 2005 and in January, 2006. The spectral analysis of variations in the maximum observed frequency (MOF) is performed. It is shown that the spectra of the MOF fluctuations have a well pronounced line structure. The amplitude-dominant spectral harmonics are concentrated near the frequencies 0.18–0.8 mHz (20–90-min periods). We give the results of modeling of radio waves propagation in the presence of traveling ionospheric disturbances and compare the calculated and experimental data. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radio.zika, Vol. 49, No. 12, pp. 1015–1029, December 2006.