Solar radio type III bursts and coronal density structures

The comparison of solar radio type III bursts measured at 169 MHz with K corona observations leads to the conclusion that about 75% of the active regions over which type III bursts occur are associated with low density coronal structures. The comparison with X-ray maps of the solar disk shows that all these regions are located in low intensity regions.It is concluded that the idea generally accepted that the type III bursts are associated with dense coronal structures and travel in these structures is not at all proven for a large number of cases.     

Coronal index of solar activity: Years 1939–1963

A coronal index of solar activity (CI), based upon the total irradiance of the coronal 530.3 nm green line, has been constructed for the period 1939–1963 from observations at five stations worldwide. The monthly average CI exhibits a cyclic pattern with time, with succesive peaks monotonically increasing since solar cycle 18. Potential uses of the CI are discussed.     

Combined fitting of Ulysses/COMPTEL GRB spectra

This paper describes a comparison of observations of the HH 30 jet/counterjet system and theoretical models of jets propagating in a strongly stratified medium. We find that the observed westward bending of the HH 30 jet and counterjet can be explained as the result of a plane-parallel pressure stratification of the surrounding environment. This model predicts specific properties for the kinematics of the outflow, that could be straight-forwardly checked with future spectroscopic and proper motion studies of HH 30.     

Preliminary results of optical searches of IPN3 localizations

We present preliminary results from deep optical searches of small (5 arcmin²) GRB error boxes determined using the Third Interplanetary Network (IPN³). Two of these fields also have been found to have historical OT events located within the IPN³ error boxes. We compare the preliminary results of these searches to those reported for the larger IPN¹ error boxes. The small size of the IPN³ error boxes should allow a test of the hypothesis suggested by the IPN¹ study that there are excess QSOs associated with the GRB fields.     

Vinciennite and Cu-excess tennantite from the Layo (Cu,Sn, As,Au) epithermal deposit (Southern Peru)

Summary The Layo epithermal deposit, cutting Miocene-Pliocene calc-alkaline volcanites of the Tacaza group, includes a well-developed eastern zone (Vetas 7 and 8) in which brecciated and banded textures are associated with a large, intensely argillized zone containing diaspore and alunite. The vetas contain a typical Cu-As mineralogy of the acid-sulfate type (pyrite, enargite, Cu-excess tennantite, chalcopyrite, covellite) with an associated original stanniferous paragenesis including vinciennite and mawsonite. The vinciennite is close to the ideal end-member (Cu₁₀Fe₄SnAsS₁₆) and the Cu-excess tennantite (Cu₁₁FeAs₄S₁₃) shows a total absence of Zn and Ag; its very specific chemical composition suggests that all the iron is Fe³⁺, equilibrated by Cu⁺ and probably minor Cu²⁺.This particular mineralogical association implies deposition at relatively low temperature (300°C) and high aS₂ (10^–6.5 decreasing to 10^–8.5), from a Cu-S-rich and Fe-Zn-poor fluid. The acid-sulfate epithermal mineralization of the eastern vetas of Layo appears to have preceded an adularia-sericite epithermal mineralization expressed in the western vetas of Layo and also in the nearby large epithermal veins at Orcopampa and Shila. It also supports the genetic relationship that is commonly evoked between porphyry copper and epithermal deposits.

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Le minéralogie originale à vinciente et tennantite riche du gisement épithermal (Cu, Sn, As, Au) de Layo (Sud Péru)

Résumé Le gîte épithermal de Layo est encaissé dans les volcanites calco-alcalines Miocène-Pliocène du groupe de Tacaza. Sa zone orientale renferme des corps minéralisés (Vetas 7 et 8) bien développés, à textures bréchiques et rubanées associées à une large zone intensément argilisée contenant diaspore et alunite.Les vetas présentent une association minéralogique à As-Cu typique des gisements acide-sulfate (pyrite, énargite, tennantite riche en cuivre, chalcopyrite, covellite) et une paragenèse stannifère originale renfermant vinciennite et mawsonite. La vinciennite est proche du pôle théorique (Cu₁₀Fe₄SnAsS₁₆) et la tennantite riche en Cu (Cu₁₁FeAs₄S₁₃) est dépourvue de Zn et de Ag; sa composition chimique suggère que tout le fer se présente sous la forme Fe³⁺, en équilibre avec Cu⁺, avec probablement une participation mineure de Cu²⁺.Cette association minéralogique particulière implique une mise en place sous forte fugacité en soufre (aS₂ = 10^–6.5 décroissant jusqu'à 10^–8.5) à une température relativement basse de l'ordre de 300°C à partir d'un fluide riche en Cu et S et pauvre en Fe et Zn. La minéralisation de type acide-sulfate des vetas orientales de Layo précéderait celles de type adulaire-sericite des vetas occidentales de Layo et des gisements voisins de Orcopampa et Shila. Elle contribue à renforcer le lien fréquemment évoqué entre les porphyres cuprifères et les gisements épithermaux.

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With 10 Figures     

On the quality of resonant absorption as a coronal loop heating mechanism

The qualityQ of a resonance is defined as the ratio of the total energy contained in the system to the dissipation per driving cycle. Hence, a good quality resonance is one with little losses, i.e., little dissipation per driving cycle. However, for heating coronal plasmas by means of resonant absorption of waves, bad quality resonances are required. Here, the quality of the MHD resonances that occur when an inhomogeneous coronal loop is excited by incident waves is investigated for typical coronal loop parameter values in the frame work of linear, resistive MHD. It is shown that the resonances in coronal loops have bad quality and, hence, yield a lot of Ohmic heating per driving cycle compared to the total energy stored in the loop. As a consequence, the time scales of the heating process are relatively short and resonant absorption turns out to be a viable candidate for the heating of the magnetic loops observed in the solar corona.     

Austauschuntersuchungen mittels luftelektrischer Messungen

Zusammenfassung Die bekannten Parallelen im tagesperiodischen Verhalten von Dampfdruck und Potentialgefälle in verschiedenen Höhen sind als Auswirkungen der gleichen Grunderscheinung des atmosphärischen Massenaustausches zu werten. Es liegt nahe, beide Elemente gemeinsam zu Austauschuntersuchungen heranzuziehen. Die Möglichkeiten, luftelektrische Untersuchungen in verschiedenen Höhenniveaus für solche Zwecke zu benutzen, werden im einzelnen diskutiert.

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Summary The well known parallels between vapour-pressure and potentialgradient with regard to their diurnal variation in different heights results from the same basic element, the atmospheric mass exchange. It is obvious to use a combination of both elements for an investigation of the exchange. In this paper the possibilities for a utilisation of measurements of the atmospheric electricity in different heights for such purposes are discussed in detail.

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Résumé Le parallélisme bien connu entre la variation diurne de la pression de vapeur d'eau et du gradient de potentiel électrique à différents niveaux peut être regardé comme l'effet du même phénomène de l'échange turbulent de l'atmosphère. Il est donc légitime d'employer ces deux éléments pour l'étude de l'échange turbulent. On discute ici en détail les possibilités d'étudier à cet effet les mesures de l'électricité atmosphérique faites à différentes altitudes.

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Mit 3 Textabbildungen.     

Buchbesprechungen

Ohne Zusammenfassung