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The paper presents a concept of the ECE diagnostic for the TRT facility and estimates the achievable measurement parameters in the baseline scenario. The target spectral region for the diagnostic corresponds to the first harmonic of the ECR frequency in ordinary polarization (O1) and the second harmonic in extraordinary polarization (X2). It is proposed to carry out measurements from the low-field side along two lines of sight: radial and toroidally oblique. The accessible spectral region in terms of the normalized radial coordinate is approximately estimated as –0.9 to 0.9 and –0.1 to 0.9. It is proposed to shape the input wave beam by means of a quasi-optical focusing system that provides a transverse size of the resolved region of approximately 3–5 cm for O1 and 1.2–3 cm for X2. For measurements, it is proposed to use Fourier transform spectrometers with a time resolution of about 10 ms and multichannel heterodyne receivers with a time resolution of about 1 μs. The minimum radial size of the resolved region is estimated to be 3–5 cm for O1 and 2–4 cm for X2, depending on the coordinate. [ABSTRACT FROM AUTHOR]

The article presents the results of estimating the parameters of the signals of the vertical channel of the microwave interferometer of the T-15MD tokamak with a probing wavelength of 0.9 mm. The estimation of parameters consisted of calculating the value of the phase shift due to the presence of plasma as well as estimating the frequency shift of the measuring intermediate frequency (IF) signal caused by the phase shift. These values determine the requirements for the measuring range, speed, and accuracy of the equipment for measuring the phase of the interferometer signals. The phase shift value is calculated for a range of average plasma densities from 1 × 1019 to 1 × 1020 particles/m3 and is from 5 to 80 fringes of 2π for circular and elongated plasma-filament configurations, respectively. The frequency shift of the microwave interferometer IF signal is estimated by scaling the experimental data from the microwave interferometer of the T-10 tokamak. For the discharge with the maintenance of the set level of electron density through a feedback system on the working gas injection into the T-10 tokamak chamber, this value is 2 kHz, and in the discharge with a deuterium pellet injection, the IF shift reaches 20 kHz. In such discharges, the expected value of the frequency shift of the IF signal of the vertical channel of the microwave interferometer of T-15MD tokamak reaches 5 and 100 kHz, respectively, and the increase in plasma density caused by the pellet injection is scaled accordingly. Pellet injection into the T-15MD tokamak plasma using the injector from the T-10 tokamak is also simulated. In this case, the IF shift value reaches 10 kHz. [ABSTRACT FROM AUTHOR]

The relationship between polar mesosphere summer echoes (PMSE) and geomagnetic disturbances (represented by magnetic K indices) is examined. Calibrated PMSE reflectivities for the period May 2006-February 2012 are used from two 52.0/54.5MHz radars located in Arctic Sweden (68° N, geomagnetic latitude 65°) and at two different sites in Queen Maud Land, Antarctica (73°/72° S, geomagnetic latitudes 62°/63°). In both the Northern Hemisphere (NH) and the Southern Hemisphere (SH) there is a strong increase in mean PMSE reflectivity between quiet and disturbed geomagnetic conditions. Mean volume reflectivities are slightly lower at the SH locations compared to the NH, but the position of the peak in the lognormal distribution of PMSE reflectivities is close to the same at both NH and SH locations, and varies only slightly with magnetic disturbance level. Differences between the sites, and between geomagnetic disturbance levels, are primarily due to differences in the high-reflectivity tail of the distribution. PMSE occurrence rates are essentially the same at both NH and SH locations during most of the PMSE season when a sufficiently low detection threshold is used so that the peak in the lognormal distribution is included. When the local-time dependence of the PMSE response to geomagnetic disturbance level is considered, the response in the NH is found to be immediate at most local times, but delayed by several hours in the afternoon sector and absent in the early evening. At the SH sites, at lower magnetic latitude, there is a delayed response (by several hours) at almost all local times. At the NH (auroral zone) site, the dependence on magnetic disturbance is highest during evening-to-morning hours. At the SH (sub-auroral) sites the response to magnetic disturbance is weaker but persists throughout the day. While the immediate response to magnetic activity can be qualitatively explained by changes in electron density resulting from energetic particle precipitation, the delayed response can largely be explained by changes in nitric oxide concentrations. Observations of nitric oxide concentration at PMSE heights by the Odin satellite support this hypothesis. Sensitivity to geomagnetic disturbances, including nitric oxide produced during these disturbances, can explain previously reported differences between sites in the auroral zone and those at higher or lower magnetic latitudes. The several-day lifetime of nitric oxide can also explain earlier reported discrepancies between high correlations for average conditions (year-by-year PMSE reflectivities and K indices) and low correlations for minute-to-day timescales. [ABSTRACT FROM AUTHOR]

Tropopause folds are one of the mechanisms of stratosphere-troposphere exchange, which can bring ozone rich stratospheric air to low altitudes in the extra-tropical regions. They have been widely studied at northern mid- or high latitudes, but so far almost no studies have been made at mid- or high southern latitudes. The Moveable Atmospheric Radar for Antarctica (MARA), a 54.5MHz wind-profiler radar, has operated at the Swedish summer station Wasa, Antarctica (73° S, 13.5° W) during austral summer seasons from 2007 to 2011 and has observed on several occasions signatures similar to those caused by tropopause folds at comparable Arctic latitudes. Here a case study is presented of one of these events when an ozonesonde successfully sampled the fold. Analysis from European Center for Medium Range Weather Forecasting (ECMWF) is used to study the circumstances surrounding the event, and as boundary conditions for a mesoscale simulation using the Weather Research and Forecasting (WRF) model. The fold is well resolved by the WRF simulation, and occurs on the poleward side of the polar jet stream. However, MARA resolves fine-scale layering associated with the fold better than the WRF simulation. [ABSTRACT FROM AUTHOR]

Comprehensive analysis of the wave activity in the Antarctic summer mesopause is performed using polar mesospheric summer echoes (PMSE) measurements for December 2010-January 2011. The 2-day planetary wave is a statistically significant periodic oscillation in the power spectrum density of PMSE power. The strongest periodic oscillation in the power spectrum belongs to the diurnal solar tide; the semi-diurnal solar tide is found to be a highly significant harmonic oscillation as well. The inertial-gravity waves are extensively studied by means of PMSE power and wind components. The strongest gravity waves are observed at periods of about 1, 1.4, 2.5 and 4 h, with characteristic horizontal wavelengths of 28, 36, 157 and 252 km, respectively. The gravity waves propagate approximately in the west-east direction over Wasa (Antarctica). A detailed comparison between theoretical and experimental volume reflectivity of PMSE, measured at Wasa, is made. It is demonstrated that a new expression for PMSE reflectivity derived by Varney et al. (2011) is able to adequately describe PMSE profiles both in the magnitude and in height variations. The best agreement, within 30 %, is achieved when mean values of neutral atmospheric parameters are utilized. The largest contribution to the formation and variability of the PMSE layer is explained by the ice number density and its height gradient, followed by waveinduced perturbations in buoyancy period and the turbulent energy dissipation rate [ABSTRACT FROM AUTHOR]