Ionospheric tomography using GNSS: multiplicative algebraic reconstruction technique applied to the area of Brazil

Experimental analysis was performed using multiplicative algebraic reconstruction technique (MART) to map the ionosphere over Brazil. Code and phase observations from the global navigation satellite system (GNSS) together with the international reference ionosphere (IRI) enabled the estimation of ionospheric profiles and total electron content (TEC) over the entire region. Twenty-four days of data collected from existing ground-based GNSS receivers during the recent solar maximum period were used to analyze the performance of the MART algorithm. The results were compared with four ionosondes. It was demonstrated that MART estimated the electron density peak with the same degree of accuracy as the IRI model in regions with appropriate geometrical coverage by GNSS receivers for tomographic reconstruction. In addition, the slant TEC, as estimated with MART, presented lower root-mean-square error than the TEC calculated by ionospheric maps available from the International GNSS Service (IGS). Furthermore, the daily variations of the ionosphere were better represented with the algebraic techniques, compared to the IRI model and IGS maps, enabling a correlation of the elevation of the ionosphere at higher altitudes with the equatorial ionization anomaly intensification. The tomographic representations also enabled the detection of high vertical gradients at the same instants in which ionospheric irregularities were evident.     

Chemical and petrologic trends in anorthositic and associated rocks of the Nain massif, Labrador

Two rock series are distinguished in the Nain anorthosite massif: the anorthosite-adamellite suite, occupying most of the massif, and the troctolite-syenite suite, which occurs in layered intrusions. Field relations show that troctolitic rocks intrude anorthositic rocks, but are intruded by adamellitic rocks.

The following evolutionary model is suggested for the Nain massif. Fractional crystallization in a parental magma resulted in a density-stratified magma mass in which plagioclase crystals accumulated by suspension at a level where the density of crystal and liquid matched. Thus, a plagioclase cumulate formed, which was underlain by heavier troctolitic magma and overlain by lighter acidic magma. Settling of the plagioclase mass caused local intrusion of troctolitic magma, which differentiated in members of the troctolite-syenite suite. Subsequent disturbance of the magma chamber distorted the solidified portion, and caused local intrusive relationships between it and the acidic rest magma, which further differentiated in members of the adamellite series.     

Zur Bedeutung der Diffusion bei der Metamorphose des Schnees

Zusammenfassung Der Diffusionsstrom des Wasserdampfes in Schnee und dessen Anteil am Stoffumsatz wird unter vereinfachenden Annahmen über die Schneestruktur und den Mechanismus der Diffusion berechnet. Für einen linearen Temperaturverlauf im Schnee folgt ein Abbau von Substanz an der warmen Begrenzungsfl?che und eine daran anschlie?ende, nach der kalten Seite hin abnehmende Verdichtung. Der so berechnete Umsatz ist quantitativ nicht ausreichend für die Deutung der Schneemetamorphose, so da? noch andere Prozesse wie Thermodiffusion am Austausch beteiligt erscheinen.

---

Summary The diffusion of water vapor in snow and its influence on the mass exchange is calculated under simplifying assumptions on the snow structure and the mechanism of diffusion. With a constant temperature gradient in a snow body a loss of solid substance is obtained on the warm boundary of the sample and adjacently a condensation in the snow which decreases toward the cold end. The computed mass transfer is not quite sufficient for interpreting the metamorphism of snow. Other processes such as thermodiffusion seem to be involved in the mass exchange.

---

Résumé Le courant de diffusion de la vapeur d'eau dans la neige et sa contribution à l'échange de matière sont calculés en adoptant des hypothèses simplificatrices pour la structure de la neige et le mécanisme de la diffusion. Avec un gradient de température constant, il se produit sur la surface chaude une évaporation, juxtaposée à une zone de condensation décroissante vers le c?té froid. L'échange ainsi calculé ne suffit pas quantitativement à expliquer la métamorphose, ce qui indique que d'autres phénomènes, tels que la thermodiffusion contribuent aux échanges.

---

---

Mit 1 Textabbildung

---

Herrn Dr.W. M?rikofer zu seinem 70. Geburtstag gewidmet.     

Die Farbe des Himmels: II

Zusammenfassung Unter Verwendung der in einer früheren Untersuchung(1) mitgeteilten Formeln werden Farbton, Sättigung und Leuchtdichte des gesamten Himmels unter exakter Berechnung der sekundären Streuung in einer dunstgetrübten Atmosphäre bestimmt. Es zeigt sich dabei, dass der vonWiener undBernhardt gemachte Versuch, die Vielfachstreuung durch Einsetzen und Summieren einer geometrischen Reihe für primäre, sekundäre usw. Streuung zu approximieren, fehlerhafte Ergebnisse liefern muss, weil das Verhältnis sekundär: primär stellenweise>1 wird. In dem durch die Sonne gehenden Horizontalkreis bleiben Farbton und Sättigung konstant und nur die Leuchtdichte ändert sich in den Fällen, dass lediglich die molekulare Streuung (ungetrübte Atmosphäre) oder lediglich die Dunststreuung (grosse Trübung, nahe der Sonne) wirksam ist.—Der Einfluss einer geänderten Grössenverteilung des Aerosols wird untersucht.

---

Summary Using formulas given in a former investigation (1), we computed the colour, saturation and brightness of the whole sky. With this, the secondary scattering of a turbid atmosphere was exactly determined. It is shown that wrong values will result by use ofWiener's method of approximating the multiple scattering by a geometrical series of primary, secondary a.s.o. scattering, because at some parts of the sky the proportion of secondary: primary is >1. In the horizontal circle through the sun, colour shade and saturation are constant and only the brightness varies, if either only molecular scattering (unturbid atmosphere) or only haze scattering (strong turbidity, small distance from the sun) dominates. Further, the influence of variations of the seize distribution of the aerosol is investigated.

---

Résumé En utilisant les formules communiquées dans une publication antérieure (1) la couleur, la saturation et la luminosité du ciel entier sont calculés en tenant compte de la réfraction secondaire dans une atmosphère brumeuse. On constate que l'essai deWiener etBernhardt d'approcher la réfraction multiple par une progression géométrique pour la réfraction primaire, secondaire etc. doit mener à des faux résultats parce que la proportion de secondaire: primaire devient en partie >1. Dans le plan horizontal passant par le soleil, la couleur et la saturation restent de même; seulement la luminosité change dans le cas ou seul la réfraction moléculaire (atmosphère non troublée) ou seul la réfraction brumeuse (beaucoup de brume, tout près du soleil) sont efficaces. L'influence d'une autre répartition de grandeur de l'aérosole est examinée.

     

Sobre un volcán de Verita recientemente descubierto en el Mioceno de Barqueros. — (Murcia)

While working to construct a geological map. A.Almela, an Engineer of Mines, discovered in Alhama de Murcia a previously unknown volcanic crater. This volcano erupted through the miocene layers and extended above them, thus establishing the date of this eruption as being post-miocene. Since there are no sedimentary rocks in this region of a more recent date it is impossible to fix the date of the eruption any more exactly. The crater is about 1Km. In the surface of the crater one finds slag, scoriaceous lava and compact rocks. The rock is composed of phlogopite, olivine and diopside in phenocrysts in a hyaloid cement with tiny grains of sanidine, olivine and diopside; and a thin layer of phlogopite in a glassy brownish black. A study was made of the chemical constituency of the rocks on the basis of three complete analyses and a comparison was made with the findings already made by Vera-Garrucha and those of Fortuna. All of the data as compiled in the five tables and four diagrams graphically represents the obtained results. The volcanic rocks have a close analogy to those ofOsann’s « Verita » type, which are shown not only by the analytical value of the magmatic parameters but also by the positions of the points shown in diagramsK-mg andLs-Fs-Ks of the three types already analized. In all the samples which have been studied from Barqueros the value of the K₂O is superior to that of Na₂O; it is also greater than that of Vera-Garrucha and less than in that of Fortuna.