Earlier interaction of indole-3-carbinols with L-ascorbic acid and chemical and biological properties of formed 2-skatylderivatives of L-ascorbic acid (ascorbigens) were discussed. In this ...presentation the properties and stereochemistry of products of interaction of polyfunctional biologically important indole-3-carbinols (indoleglycerol analogs and beta-hydroxytryptamine derivatives) with L-ascorbic acid are investigated. Biological significance of this reaction is discussed.
Research on the character of Georgian verse started in 1731. Since that time, some researchers have described Georgian verse as syllabic, while others have said that it is syllabotonic. The dispute ...about the character of Georgian verse became particularly acute in the 20th century. The main text the participants in the dispute analysed was a prominent piece of Georgian poetry of the 12th century – The Knight in the Panther’s Skin by Shota Rustaveli. It consists of 16-syllable monorhymical quatrains that have a special name in Georgian – shairi. There are two varieties of shairi – the so-called high shairi (4 4 4 4) and low shairi (5 3 5 3). The high shairi was the main issue of the dispute. The researchers who regarded Georgian verse as belonging to the syllabotonic system divided high shairi into trochaic feet, while the supporters of the syllabic theory denied the presence of metric trochaic stress in high shairi, believing that the penultimate syllables can be stressed only in two-syllable words but not in words with multiple syllables (due to the dactylic accentuation typical in the modern Georgian language).
Since natural dactylic stress (found in low shairi) reflects the accentuation norms of the language of the later period (including those of modern Georgian), we assume that metric stress in high shairi, which is no longer found in modern Georgian speech, could be a reflection of the natural accentuation of the comparatively earlier period in the development of the Georgian language. Checking this hypothesis by relying on relevant linguistic literature, we reconstructed the archaic movable and phonologically relevant stress in the rhymed words in The Knight in the Panther’s Skin. We found that metric stresses of both high and low shairi in this epic poem are actually archaic linguistic stresses. This conclusion differs from the views expressed in concepts developed earlier. It enables us to take a fresh look at the metrics and rhymes of The Knight in the Panther’s Skin as well as the main principles and specific features of Georgian verse in general.
Storm-time topside ionosphere plasma composition, especially the light ion fraction, is an important parameter which controls magnetosphere–ionosphere coupling, plays a part in the growth of local ...instabilities, and provides information about the ring current, ion upflow, movement of ionization and other important physical processes and parameters. Ion composition is difficult to estimate on fine scales as empirical models tend to be parametrized by fixed inputs, ignoring the role of memory in plasma, and to preferentially capture large scales, while ground radars have limited coverage. In particular, ionospheric composition measurements at mid-latitude are lacking. Here we show, using the new Swarm SLIDEM effective ion mass measurement, a superposed epoch analysis of storm-time dayside and nightside effective ion mass changes, demonstrating the extent and timescales of motion of the O+/H+ transition height with the main phase of geomagnetic storms, as well as directly observing evidence for the latitude dependence of these dynamics.
Graphical Abstract
Ionospheric electrodynamics is a problem of mechanical stress balance mediated by electromagnetic forces. Joule heating (the total rate of frictional heating of thermospheric gases and ionospheric ...plasma) and ionospheric Hall and Pedersen conductances comprise three of the most basic descriptors of this problem. More than half a century after identification of their central role in ionospheric electrodynamics, several important questions about these quantities, including the degree to which they exhibit hemispheric symmetry under reversal of the sign of dipole tilt and the sign of the y component of the interplanetary magnetic field (so-called “mirror symmetry”), remain unanswered. While global estimates of these key parameters can be obtained by combining existing empirical models, one often encounters some frustrating sources of uncertainty: the measurements from which such models are derived, usually magnetic field and electric field or ion drift measurements, are typically measured separately and do not necessarily align. The models to be combined moreover often use different input parameters, different assumptions about hemispheric symmetry, and/or different coordinate systems. We eliminate these sources of uncertainty in model predictions of electromagnetic work J⋅E (in general not equal to Joule heating ηJ2) and ionospheric conductances by combining two new empirical models of the high-latitude ionospheric electric potential and ionospheric currents that are derived in a mutually consistent fashion: these models do not assume any form of symmetry between the two hemispheres; are based on Apex magnetic coordinates (denoted Apex), spherical harmonics, and the same model input parameters; and are derived exclusively from convection and magnetic field measurements made by the Swarm and CHAMP satellites. The model source code is open source and publicly available. Comparison of high-latitude distributions of electromagnetic work in each hemisphere as functions of dipole tilt and interplanetary magnetic field clock angle indicates that the typical assumption of mirror symmetry is largely justified. Model predictions of ionospheric Hall and Pedersen conductances exhibit a degree of symmetry, but clearly asymmetric responses to dipole tilt and solar wind driving conditions are also identified. The distinction between electromagnetic work and Joule heating allows us to identify where and under what conditions the assumption that the neutral wind corotates with the Earth is not likely to be physically consistent with predicted Hall and Pedersen conductances.
Current methods for estimating ion density on Swarm rely on the assumption of 100% O + and no along-track ion velocity flows. These assumptions are routinely violated, particularly on the nightside ...and during high-latitude and polar cap traversals, compromising the accuracy of the measurements. The use of faceplate current data along with the Langmuir probe ion admittance measurements, and orbital-motion limited (OML) theory, make it possible to relax some of the assumptions inherent in current ESA Swarm density estimates. This further yields along-track ion drift and effective ion mass estimates. This paper describes the theoretical basis for estimating revised ion density, providing a new estimate for effective ion mass, as well as an alternative way of estimating along-track ion drift. The complete Swarm historical data set has been generated and validated using empirical models (International Reference Ionosphere, and an empirical electric field model), as well as ground-spacecraft conjunctions. Case studies and statistical results reveal clear geophysical signatures in the new product of light ions at low- and mid-latitudes and along-track ion drift at high latitudes, and their response to space weather.
Graphical Abstract
Key points
A new data product for Swarm along-track ion drift velocity, density and effective mass has been derived
The addition of faceplate current to ion admittance enables a refinement to Swarm ion density
The estimations have been validated against a variety of independent measurements and empirical models
In this study we calibrate and validate in situ ionospheric electron density (Ne) and temperature (Te) measured with Langmuir probes (LPs) on the three Swarm satellites orbiting the Earth in ...circular, nearly polar orbits at ~500 km altitude. We assess the accuracy and reliability of the LP data (December 2013 to June 2016) by using nearly coincident measurements from low‐ and middle‐latitude incoherent scatter radars (ISRs), low‐latitude ionosondes, and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites, covering all latitudes. The comparison results for plasma frequency (
f∝Ne) for each Swarm satellite are consistent across these three, principally different measurement techniques. It shows that the Swarm LPs systematically underestimate plasma frequency by about 10% (0.5–0.6 MHz). The correlation coefficients are high (≥0.97), indicating accurate relative variation in the Swarm LP densities. The comparison of Te from high‐gain LPs and those from ISRs reveals that all three satellites overestimate it by 300–400 K but exhibit high correlations (0.92–0.97) against the validation data. The low‐gain LP Te data show larger overestimation (~700 K) and lower correlation (0.86–0.90). The adjustment of the Swarm LP data based on Swarm‐ISR comparison results removes the systematic biases in the Swarm data and gives plasma frequencies and high‐ and low‐gain electron temperatures that are precise within about 0.4 MHz (8%), 150–230 K, and 260–360 K, respectively. We demonstrate that the applied correction significantly improves the agreement between (1) the plasma densities from Swarm, and from ionosondes and COSMIC, and (2) the Te from Swarm LPs and International Reference Ionosphere 2016.
Key Points
Swarm Langmuir Probe (LP) data are compared to independent ground‐ and space‐based measurements
Initial Swarm LP data show systematic errors but high correlations with data from other techniques
Adjustments based on incoherent scatter radar data significantly improve the accuracy of LP data
The terrestrial ionosphere displays significant equinoctial asymmetry despite the upper atmosphere receiving similar levels of solar ionization energy at a given location and local time in March and ...September during similar solar activity conditions. This intriguing feature is not well understood or modeled, particularly in the upper ionosphere, and causes of the asymmetry are not fully established and quantified. Yet, their study is important to provide better insights into the atmosphere‐ionosphere coupling processes. Analysis of Langmuir probe data from ESA's Swarm B satellite at ∼525 km altitude reveals that the daytime electron density is larger for all latitudes during the March equinox than during the September equinox, while the electron temperature shows an inverted asymmetry except at low latitudes. Simultaneously obtained neutral density data from Swarm GPS accelerations indicate that the thermosphere is denser during the March equinox. The asymmetry seen by Swarm electron density observations is also present in electron densities obtained using GPS radio occultation measurements from the COSMIC satellites. Simulations were performed using physics‐based ionosphere models (SAMI3, WACCM‐X, and TIE‐GCM) to determine their ability to produce the observed asymmetry, understand the generation mechanism(s), and establish the relative role of physical drivers. Results produced by TIE‐GCM are closest to the observations when seasonally varying eddy diffusivity is considered in the model. The asymmetry produced by other models is noticeably weaker. Modeling of the asymmetry by SAMI3 driven with the TIE‐GCM neutral atmosphere shows that both neutral density and winds play a critical role, but the density has a greater effect.
Key Points
Analysis of Swarm and COSMIC satellite observations reveals significant equinoctial asymmetry in the upper ionosphere
Electron and neutral densities are larger in March than September; electron temperature shows a reversed asymmetry except at low latitudes
TIE‐GCM with variable eddy diffusivity produces results closest to the observations; both neutral density and winds play an important role
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