Studying travelling ionospheric disturbances from near-vertical ionosphere sounding with high temporal resolution
In this study, we analyze the near-vertical ionospheric sounding data obtained with a multipurpose digital chirp ionosonde. The ionosonde was recording ionograms once each minute. We analyzed the results of processing the datasets over three observational years from 2010 to 2012. Obtaining ionograms with a high temporal resolution allowed us to trace the dynamics and evolution of additional traces referred to as “cusps”, and also to combine ionograms with such traces into sequences. The percentage of ionograms containing cusps proved to be more than 10% of the overall number of ionograms. Thus, during daytime, the rate surpasses 30%, whereas, during nighttime, such ionograms are practically absent. The typical cusp lifetime proved to be 4-15 min, therefore, disturbed ionograms are much more rarely detected with standard vertical sounding ionosondes. The presence of such traces unambiguously evidences significant electron density horizontal gradients caused by travelling ionospheric disturbances (TIDs) with scales up to 50 km.
Vertical midscale ionospheric disturbances caused by surface seismic waves based on Irkutsk chirp ionosonde data in 2011–2016
Based on the Irkutsk fast monostatic chirp ionosonde data, we made a statistical analysis of ionospheric effects for 28 earthquakes which appeared in 2011–2016 years. These effects are related with surface (Rayleigh) seismic waves far from epicenter. The analysis has shown that nine of these earthquakes were accompanied by vertical midscale ionospheric irregularities (multicusp). To estimate the ionospheric efficiency of the seismic waves, we proposed new index KW. The index estimates the maximal amplitude of the acoustic shock wave generated by given spatial distribution of seismic vibrations and related with maximal spectral power of seismic oscillations. Based on the analysis of experimental data, we have shown that earthquake‐related multicusp (5–25 s irregularities) is observed mostly at daytime [07:00–17:00] LST for KW≥4.7. The observations of acoustic waves by GPS technique in the epicenter vicinity (120–600 s irregularities) do not show such a daytime dependence. Based on 24 May 2013 Okhotsk Sea earthquake example, we demonstrated that deep‐focus earthquakes can produce strong multicusp far from the epicenter, although do not produce significant GPS ionospheric response in the epicenter vicinity.
Full-scale measurements of SO2 gas phase concentrations and slurry compositions in a wet flue gas desulphurisation spray absorber
Abstract Two measurement campaigns were carried out at ENERGI E2's Asnaes Power plant, unit 5. The unit has a capacity of 620 MW e and is equipped with a wet flue gas desulphurisation (FGD) plant employing a counter-current spray absorber with five spray levels. In the first campaign, the power plant was firing Orimulsion ® with 2.85 wt% S resulting in a flue gas concentration of SO 2 exceeding 2000 ppmv. In the second campaign, the fuel applied was a low-S blended coal and the SO 2 concentration in the raw gas was around 400 ppmv. A novel probe for in situ sampling of gas phase concentrations in wet FGD spray absorbers was developed and applied for measuring axial profiles of the SO 2 gas phase concentrations in the absorber. The expected decrease in SO 2 concentrations along the height of the absorber was found in the spray section (from height 26.5 to 36.2 m) whereas the SO 2 concentration above the holding tank and below the gas inlet was quite low probably due to long local residence times in the region. Horizontal variations, due to somewhat different flow conditions near the column wall were investigated and the SO 2 concentrations were found to be higher near the wall. Measurements at different gross loads showed that the SO 2 gas phase concentration at a given position inside the absorber was roughly linearly related to the L/G ratio in the measuring interval. Turning off one of the lower spray levels, while burning coal with low S content, did not lower the overall removal efficiency of the absorber. However, the SO 2 gas phase concentration inside the lower part of the absorber was increased by a factor of 2–3. Measurements of slurry pH at different positions showed a decrease of approximately 0.5 units from the upper to the lower part of the absorber. The full-scale measurements provide a detailed set of experimental data for validation of mathematical models of a wet FGD spray absorber.