Modification of the strato-mesospheric temperature and wind structure resulting from the 26 February 1979 solar eclipse

Temperature and wind behavior observed during the February 1979 solar eclipse shows significant change immediately following and up to one hour after totality. Statospheric and mesospheric data obtained from Fort Churchill, Manitoba, indicate quite clearly a cooling trend between 50–60 kilometers with the maximum temperature decrease of approximately 10°C evident above 52 kilometers. This temperature perturbation was accompanied by an amplification of the meridional wind speed of 20–30 mps near 60 kilometers. These results are essentially in agreement with those obtained at Wallops Island during the March 1970 solar eclipse. Although the stratosphere was under the large-scale influence of a stratospheric warming, the short-term perturbations caused by radiative changes as a result of the solar eclipse did not appear to be masked.     

26 February 1979 total solar eclipse induced LF (60 kHz) phase retardation

The LF phase retardation induced by the total solar eclipse of Monday, 26 February 1979 and observed by monitoring the 12.5 km path length 60 kHz WWVB transmission from Fort Collins, U.S.A., to Calgary, Canada, as the path of totality at the 80 km height of the D-layer swept over Billings, Montana, U.S.A., near the midpoint of this transmission path is reported.     

Positive and negative ion composition measurements in the D- and E-regions during the 26 February 1979 solar eclipse

Two rockets bearing quadrupole mass spectrometers capable of measuring both positive and negative ion composition were launched from Red Lake, Canada, during the solar eclipse. Both instruments had liquid helium cryopumps and shock-attaching conical samplers. The payloads also contained two Gerdien condensers to measure total positive and negative ion concentrations and ion mobilities. Attitude control systems aligned the payloads with the velocity vector throughout ascent and descent. The first rocket was launched so that the D-region was in darkness 35 ± 8 s on the upleg and about 150 ± 15 s on the downleg for the study of ionospheric decay processes. The second rocket was fired after totality into 75% solar illumination for the study of ionospheric recovery. The positive ion composition above 105 km exhibited a strongly increasing NO⁺/O₂⁺ ratio with time after second contact due to O₂⁺ charge transfer with NO and a sharply diminished ionization rate. However, in both nights, the ionization below 105 km was created mainly by energetic particle deposition as exemplified by the increased ion concentrations and the composition signatures of a particle event: asignificant enhancement of O₂⁺ below 105 km and large amounts of H₅O₂⁺ ions in the D-region which result from the O₂⁺ clustering scheme. H₅O₂ was the major ion in the upper D-region while H₇O⁺₃, H₉O₄⁺ and H₅O₂⁺ were dominant ions at lower altitudes. Numerous minor species were also detected. The negative ion distributions in both flights exhibited a distinct shelf at 83 ± 2 km, decreasing by more than an order of magnitude by 90 km and with minima near 75 km. In the 75–90 km range, a significant percentage of the negative ions had masses exceeding 160 a.m.u. Comparisons are made with prior negative ion measurements during similar daytime auroral zone absorption (AZA) events. Two striking characteristics of the precipitating particles were apparent from these and past observations in daytime AZA events: there is a near absence of low energy electrons capable of ionizing above about 105 km and there is'a significant spatial and/or temporal variability in the electron flux. This paper is devoted principally to a presentation of the ion composition measurements and associated uncertainties.     

A model of the lower ionosphere above Red Lake,Canada, during the 26 February 1979 solar eclipse

Measurements of ionization sources, ionization profiles and minor atmospheric constituents were conducted during the 26 February 1979 solar eclipse above Red Lake, Canada. A model of the lower thermosphere has developed to describe the D- and E-regions of the ionosphere for this case with the model being guided by the measurements. During the eclipse a rather intense particle precipitation event was in progress. For this reason, an auroral deposition code was coupled to a chemical-kinetics code to calculate degraded primary and secondary electron fluxes, ionization rates, positive ion and electron densities. The model was calibrated with the experimental measurements of electron flux below 100 km and electron density between 70 and 150 km. This calculation not only satisfactorily described the ionization in the E-region but also the gross electron density characteristics of the D-region. Bursts in the observed electron flux were also simulated with the model to give electron density profiles that were remarkably consistent with small perturbations seen in the electron density measurements.     

The solar eclipse of 26 February 1979: analysis and modelling of primary pair production,electron density and ionic composition

The solar eclipse of 26 February 1979 was observed from Red Lake, Canada, (52 °N, 91 °W) where totality occurred at about 1053 local time. Several research groups and government agencies participated in an extensive ground- and rocket-based observational program directed at the middle atmosphere. At the time of the eclipse, an extensive geomagnetic storm was in progress and the middle atmosphere was undergoing temperature and circulation changes associated with a stratospheric warming. Concurrent observations of atmospheric constituents, solar radiation, electron flux and other middle atmosphere parameters were obtained as inputs for a D-region predictive chemical computer code, DAIRCHEM, tailored to eclipse conditions. Ion pair production rates were computed by an E-region infrared radiance model and were used as necessary source function input values for DAIRCHEM computations. The computations yielded predictions of electron and total positive ion densities about totality. The positive ion measurements of a supersonic Gerdien condenser and a subsonic blunt probe during the eclipse were in agreement with the model computations and provided normalizing summations of total positive ions for the interpretation of mass spectrometer measurements. The chemical computer code identified principal routes for increase and removal of key species such as O₂⁺, NO⁺, hydrated clusters and negative ions. The dominant precursor ion for pair production hydrates was O₂⁺ and the chemistry was characteristic of the disturbed D-region.     

The E-region electron density diurnal asymmetry at Saint-Santin: observations and role of nitric oxide

Measurements of the E-region electron density were made with the Saint-Santin incoherent scatter radar during consecutive days in June 1978, March 1979 and December 1980. On the basis of a statistical study, the observations show the presence of a diurnal asymmetry of the electron density, with morning values usually exceeding the afternoon densities by 3–20%. Two possible causes of the dissymmetry are examined: the asymmetry in the diurnal variation of the neutral composition and the effect of nitric oxide. The presence of NO partly converts O₂⁺ into NO⁺ ions and increases the effective recombination rate of the electrons in the afternoon. Numerical simulations assessing the relative importance of the two factors are, in general, in good agreement with the measurements.     

HF Doppler observations of gravity waves during the 16 February 1980 solar eclipse

Observations by the HF Doppier technique of the ionospheric effects of the 16 February 1980 solar eclipse in Africa are presented. Some oscillations which are detected at two stations can be attributed to a travelling coherent structure. Its characteristics are consistent with a gravity wave generated by the eclipse.     

Ionospheric electron content observations during the total solar eclipse of February 16, 1980

Observations on the Faraday rotation of a transionospheric VHF signal obtained from a network of four stations near the path of totality during the total solar eclipse of 16 February 1980 are reported. A small decrease of 3–4% in the total ionization has been obtained around the time of totality. Absence of any periodic structure following the eclipse indicates that the TIDs are not of significant amplitude in the present case to be detected by the Faraday rotation technique.     

Direction of arrival of radio waves reflected from the E-region

A simple system for measuring the direction of arrival of continuous high frequency radio waves reflected obliquely from the ionosphere is described. Results obtained over a near vertical path are used to evaluate changes in the electron density gradients (tilts) in the E-region. Wave interference on the transmission due to multiple hop or ground wave propagation is discussed.     

Atomic oxygen determination from a nitric oxide point release in the equatorial lower thermosphere

Atomic oxygen density values in the 80–105 km altitude equatorial region have been obtained by analyzing the chemiluminescence of nitric oxide point releases from three CENTAURE II-C rockets. The light emission produced by the NO—O chemiluminous recombination was sufficiently high to render the artificial clouds observable only by ground-based instruments. The difficulties associated with these kind of experiments have been greatly avoided by a new technique ejecting the NO gas into the backward direction of the flight. It has been found that below 90 km the derived atomic oxygen densities are in relatively good agreement with those reported by other workers. At approximately 105 km the measured value is about two times higher than the n(O) density obtained by averaging a set of data from a great number of other nights but coincides rather well with the measurements of Dickinsonal. (1980).     

Rocket measurements of nitric oxide in the equatorial region

Measurements of nitric oxide (NO) concentrations were carried out from Thumba, India, using rocket-borne radiometers. The technique of measurement is based on the detection of day-glow emissions of the NO gamma (1,0) band. The results obtained are presented in this paper. The peak NO concentration shows a very good correlation with integrated value of the solar X-ray flux in the 0.1–0.8 nm band, thereby indicating the influence of the X-ray flux on the NO concentration. The observed variability of NO is thought to be mainly due to solar activity and partly due to different X-ray flux values on the days of the flights. Theoretical model calculations for rocket flight conditions were found to be in fairly good agreement with the observed profiles. The differences below 90 km altitude in the NO profiles are thought to be due to eddy turbulence. This model is also used to study changes in the NO concentration with solar activity and latitude.     

The impact of gravity waves on nitric oxide in the lower thermosphere

Observations of nitric oxide (NO) by the Solar Mesosphere Explorer (SME) during equinox indicate a lower-thermosphere equatorial minimum which is at variance with theoretical predictions. To address this discrepancy a zonally averaged model of the thermosphere and upper mesosphere is used to evaluate the influence of a latitude variation in turbulence. Five numerical simulations were performed with different latitude structures of eddy diffusion (K_T), ranging from uniform in latitude, peaks at low, mid-, or high-latitude, to a hemispherically asymmetric distribution. A local increase in eddy diffusion causes the lower thermosphere to cool and induces a latitude pressure gradient that drives horizontal and vertical winds. The circulation, turbulent transport and temperature dependent chemistry act to change the distribution of species. Comparison of the model predictions of NO with SME data, and simulated wind and temperature structure with empirical climatology, indicates a preference for a midlatitude peak in K_T.     

Letter from the vatican: 26 April 2015

This narrative deals with the author's experiences while attending a human trafficking panel at the Pontifical Academy of Social Sciences (PASS) in the Casina Pio IV, Vatican City, 7–21 April 2015.     

Technological traditions inferred from iron artefacts of the Xiongnu Empire in Mongolia

Iron objects excavated from sites of the Xiongnu Empire (3rd century BC–2nd century AD) in Mongolia have been examined using optical and scanning electron microscopy. The results show that the Xiongnu iron tradition may be characterized by the use of low carbon iron and carbon control by carburization. Cast iron was also used in the Xiongnu Empire, but only in very limited applications and with no convincing evidence of its use for the production of low carbon iron. The Xiongnu iron technology seems to have been established on the basis of the bloomery technique, without much influence from the Chinese style of technology, based on cast iron.