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.
Comment on “A Study of the F2 Layer Stratification on Ionograms Using a Simple Model of TIDs” by Jiang et al.
A paper by Jiang et al. (2019, https://doi.org/10.1029/2018JA026040) apparently tries to find common ground between observations of the F3 layer and TIDs by referring to the later when observed near the equatorial anomaly peak as a new type 1 and TIDs by using ray tracing models with arbitrarily adjusted TID parameters. Further confusion in conflating the two separate phenomena is created by referring to both as “stratification.” This comment points out that the F3 is a daytime temporary layer maintained by E × B uplift at the magnetic equator, normally occurs consistently within the peaks of the equatorial ionization anomaly in F2 electron density and may last for hours. Such a layer can be described as a stratification. How this effect dies out beyond the anomaly peak has yet to be experimentally ascertained. A cusp or inflection type TID is a manifestation of a gravity wave with no consistency in location and local time, of short duration measured in minutes, involving a continuous descent in height and should not be described as stratification. The theory of both is well known, and attempting to explain a possible F3 layer as a new type of layer when seen in the vicinity of an equatorial anomaly peak misunderstands the theory of the phenomenon. Attempts to characterize such a phenomenon as a TID manifestation are not defensible.
Mathematical Simulation of Combustion of Boron Powder Gas Suspension
Based on a two-phase two-velocity model of a reacting gas-dispersed medium, a mathematical model of combustion of a boron powder gas suspension has been formulated. The results of numerical solution of the problem are presented. The influence of the composition of the gas suspension, its size, size distribution of particles, mass concentration of particles, as well as of the presence of aluminum powder in the suspension on the visible and normal velocities of flame propagation in the gas suspension, is shown. A comparison of the results of calculation with the well-known experimental and theoretical data is carried out. Satisfactory agreement of the predicted results with experimental data is shown.