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The rate and direction of rift propagation through ice shelves depend on both the stress field and the heterogeneity (or otherwise) of the physical properties of the ice. The Brunt Ice Shelf in Antarctica has recently developed new rifts, which are being actively monitored as they lengthen and interact with the internal structure of the ice shelf. Here we present the results of a ground-penetrating radar survey of the Brunt Ice Shelf aimed at understanding variations in the internal structure. We find that there are flow bands composed mostly of thick (ca. 250 m) meteoric ice interspersed with thinner (ca. 150 m) sections of ice shelf that have a large proportion of sea ice and seawater-saturated firn. Therefore the ice shelf is, in essence, a series of ice tongues cemented together with ice mélange. The changes in structure are related both to the thickness and flow speed of ice at the grounding line and to subsequent processes of firn accumulation and brine infiltration as the ice shelf flows towards the calving front. It is shown that rifts propagating through the Brunt Ice Shelf preferentially skirt the edges of blocks of meteoric ice and slow their rate of propagation when forced by the stress field to break through them, in contrast to the situation on other ice shelves where rift propagation speeds up in meteoric ice. [ABSTRACT FROM AUTHOR]

Based on the results of mathematical modeling, we consider the possibility to estimate the plasma frequency F2 layer maximum of the polar ionosphere (critical frequency, foF2) using frequency-sweeping radiation from a highly elliptical spacecraft orbit in the Arctic zone. Our modeling concerning the energy problem of radio sensing consisted of analyzing wave field parameters, received field strength, and SNR on two radio paths with the distances 1900 and 2500 km along the earth's surface, with the satellite height varying from 10,000 to 30,000 km. Radio path orientations were selected to be close to the classical limit cases of radio wave propagation in the anisotropic ionospheric plasma: quasi-longitudinal approximation and, to a large extent, the quasi-transversal one for the quiet midday and midnight conditions. As a result of these simulations and following specific spacecraft conditions, working with an optimal probing signal was proposed for the appropriate emission power for the onboard transmitter. In the inverse problem of radio sounding of an ionized media, common mathematical inaccuracy in foF2 calculated from the transionogram, frequency dependence of the probing signals magneto-ionic group delay, was estimated. Considering and founding a possible realization of the method, physical prerequisites are discussed based on the experimental data of radio waves passing the 16,000 km long radio path for Moscow–Antarctica (UAS Vernadsky). [ABSTRACT FROM AUTHOR]

We address deviations in the source bearing of natural pulsed extremely low frequency (ELF) radio signals (Q-bursts) in the Schumann resonance band. The model of smooth day – night non-uniformity is used. The observer is located at the Ukrainian Antarctic station "Akademik Vernadsky" (65.25° S and 64.25° W), and the source is positioned at the same meridian at latitudes of 20° S; 25° N, or 85° N. The equinox period is considered when the solar terminator line is coincident with a meridian. Thus, the source – observer meridian and the terminator meridian are separated by an angular distance varying with the local time of observer. The propagation parameters of ELF radio waves were computed using the full wave solution in the form of Riccati equation for the ambient day and ambient night profiles of mesosphere conductivity. The field spectra were found from the 2D telegraph equations (2DTE). Spectra of the source bearing and of the polarization coefficient were computed for different local times. The source bearing and the polarization coefficient do not exceed ±15° and ±0.35 correspondingly. The Q-bursts in the time domain were computed at the output of an example Schumann resonance receiver. Phasors of the Poynting vector were used for estimating the source bearing in the time domain. Maximum deviations in the source azimuth may reach ±4° directed toward to the midnight point. The eccentricity of the "elliptic" magnetic field phasor may reach 0.1. Impact of the day – night non-uniformity is comparable with that of the continuous Schumann resonance background. Therefore, terminator effect is detectable in records of extra-powerful Q-bursts exceeding the background noise by the factor of 10–20. • Realistic model of the Earth–ionosphere cavity with the day–night non-uniformity is used. • Propagation parameters of ELF radio waves were computed using the full wave solution in the form of Riccati equation. • Spectra of vertical electric and two orthogonal horizontal magnetic fields were found using 2D telegraph equations. • Observer was at 65.25°S and 64.25°W, and the source occupied the same meridian at latitudes 20°S; 25°N, or 85°N. • The equinox period was considered when the solar terminator is coincident with a meridian. • Spectra were computed of the source bearing and of polarization coefficient for different local time of observatory. • Deviation of the source bearing may reach ±15°, and of the polarization coefficient may reach the ±0.35 interval. • The Q-bursts were computed with account for the gain of an example Schumann resonance receiver. • Time domain phasors of horizontal Poynting vector were used for estimating the source bearing. • The time domain deviations may reach ±4°, and the Poynting vector tends to point to the midnight position. • Detection of terminator effect in the source bearing is possible for Q-bursts exceeding the background by a 10–20 factor. [ABSTRACT FROM AUTHOR]

Part II. Investigates how the quassi biennial oscillation (QBO) influence on wave propagation and temperatures affects the Antarctic ozone hole. Correlation between QBO and ozone hole severity; Ozone response to QBO; Discussion and conclusions.