Connection between the upper ionospheric region of VLF chorus occurrence and the plasmapause position

Summary The occurrence zone of the VLF chorus in the upper ionosphere appears at L-shells lower than plasmapause position L_pp; with increasing geomagnetic activity the spatial dimension of the zone diminishes, its upper boundary being shifted in correspondence with the plasmapause position, the lower remaining practically without change(L=2.0÷2.5). Calculations of propagation paths have shown that the similarity of the VLF chorus spectrum at different upper-ionospheric latitudes as well as the large spatial dimension of the zone of observation can be explained as special features in the propagation of VLF waves from an equatorial source, starting in the vicinity of the plasmapause with different initial normal angles.

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a umauu u ana amu L-, u L_pp (L_pp — nu nana); uu aum amumu nmam a am, nu aua am mmmuu uu nu nana, a u mam namuu u(L=2.0÷2.5). am mamu naam, m n¶rt;u nm a au uma u, ma a nmam ama a¶rt;u, m m mu anmau m amua umua, an amu nana, uu au au.

     

On the possibilities of observing ballistic plasma wave processes in the magnetosphere

Summary The conditions are studied under which ballistic effects of transmission of waves through opacity barriers can be observed in magnetospheric experiments on board satellites. The mechanism of this effect consists of the regeneration of the radiation beyond the barrier by resonance electrons, modulated by a quasimonochromatic wave incident and reflected from the barrier. Ballistic processes in continuously inhomogeneous plasma are studied. Detailed analysis has been carried out for a barrier with a parabolic density profile. Recommendations are presented as to experimental procedures in circumterrestrial space and data processing. The possibilities are studied of observing ballistic effects in the course of active space experiments with sources of intensive broadband turbulence such as beam of charged particles, injected into the magnetosphere.

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¶rt;a u, nu m ¶rt; nmu num aum na m a¶rt;am aumuu m n¶rt;u a namu, au m mum auu uu a a au mau, n¶rt;uau auamu , na¶rt;a a a u maa m . am aumuu n na¶rt;¶rt; na. ma u n¶rt; ¶rt; aa naauu nu nmmu. a ¶rt;auu n n¶rt;u numa nmam u n am ¶rt;a. ¶rt;am m a¶rt;u aumuu m ¶rt; amu uu num umuau umu un mmmu, mauu, a nu a amu umu aum.

     

Tertiary relief generations between the Vosges and the Hunsrück mountains

After a short discussion of the older theories the geomorphological evolution between the Vosges and the Hunsrück mountains is reconstructed by evaluating geological data, comparing with neighbouring regions and taking the palaeoclimate into account.By the end of the Eocence the vast peneplain between the Vosges and the Rhenish Shield was eroded and a scarpland developed between these Hercynian blocks. As a consequence of the vigorous uplift of the Vosges during the lower and middle Oligocene the region was tilted toward the N. At the same time the scarpland was at least partially buried under its own detritus, and on the sedimentary surface thus formed the present river network developed. Since the Rhenish Shield was low lying, the watercourses were able to make their way to the N or NE without difficulty.During the Miocence the landscape was once more worn down to another peneplian which covered large parts of the Paris Basin, the Rhenish Shield and the N Vosges. The analysis of remnants of this plain shows that they cannot be explained by Schmitthenner's theory on scarplands.Erosion caused by Pliocene uplift has dissected this peneplain, and during a tectonic lull a lower surface with flat landforms came into existence.I am indebted to the Geological and Geographical Institutes of the University of the Saarland for allowing me the use of their well-equipped libraries.     

Eine kritische Bemerkung zum Neumann-Spektrum des Seeganges

Zusammenfassung Es wird darauf hingewiesen, daß das Maximum in der von G. Neumann gegebenen Form des Energiespektrums des Seeganges bei verschiedenen Perioden liegt, je nachdem das Spektrum auf die Wellenperiode oder auf die Wellenfrequenz bezogen wird. Diese Schwierigkeit wird vermieden, wenn man in beiden Darstellungsformen die Perioden bzw. Frequenzen logarithmisch unterteilt. Die neue Form des Energiespektrums führt auf eine Beziehung für die Gesamtenergie des ausgereiften Seeganges pro Flächeneinheit der Meeresoberfläche, in der die Windgeschwindigkeit-abweichend von Neumann-mit der 4. Potenz eingeht. Abschließend wird versucht, die im Energiespektrum auftretende Konstante zu bestimmen.

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A critical note on Neumann's sea spectrum

Summary It is pointed out that the maximum of the energy spectrum of sea waves, as given by G. Neumann, occurs at different periods, depending on the spectrum being referred to the period or to the frequency of the waves. This difficulty will be avoided if in both types of representation the periods or the frequencies will be divided according to the logarithmic scale. The new form of the energy spectrum will permit to set up an equation representing the total energy of the fully developed sea per unit area of sea surface; in this equation the wind velocity — contrary to Neumann — is raised to the 4th power. In conclusion, the attempt is made to determine the constant occurring in the energy spectrum.

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Note critique sur le spectre de l'état de la mer d'après Neumann

Résumé On indique que le maximum du spectre d'énergie de la mer agitée, comme G. Neumann l'a fixé, se produit dans des périodes différentes suivant que le spectre est référé à la période ou à la fréquence des vagues. On peut éviter cette difficulté si l'on applique, suivant le cas, la subdivision logarithmique aux périodes ou aux fréquences de ces deux types de représentation. La nouvelle forme du spectre d'énergie permet d'établir une équation représentant l'énergie totale de l'agitation complètement développée de la mer référée à l'unité de superficie de la surface océanique. Dans cette équation la vitesse du vent — contrairement à Neumann — est élevée à la quatrième puissance. En conclusion, on essaie de déterminer la constante présente dans le spectre d'énergie.

     

Magnetotelluric observational techniques on land

During the period since the Workshops in Sopron and Murnau we have witnessed some quite remarkable changes in the techniques employed in magnetotelluric (MT) observations. These changes have brought about significant improvements in the quality of MT data that can be gathered today. The new techniques are very likely to bring improvements in many areas beside MT, but are reviewed here in the light of the progress they have rendered possible for MT soundings on land. Three main subjects are covered in this review. The first one is concerned with the use of cryogenic or SQUID magnetometers. The new instruments are presented to the geomagnetist. An explanation of how these instruments work is given without, however, details of their operation and fabrication, and without showing that they usually have a much larger, i.e. better, signal-to-noise ratio than conventional magnetometers. Next, the method of the remote magnetic reference is examined. Originally the MT method assumed incident signals in the form of plane waves. While it is known today that incident wave amplitudes which vary linearly with distance are perfectly acceptable for MT soundings, there are many other higher order distortions of the incident signal which are not acceptable. Most of these high order or local perturbations are man-made and can seriously falsify MT data. All processes of MT data analysis try to minimize the errors caused by locally perturbed signals. But they are only partly successful, especially when the perturbations produce strong cross-power bias. The remote magnetic reference method has proved far superior in avoiding most of this cross-power as well as faulty autopower. The last section of this review deals with the use in the field of microcomputers or microprocessors. These have made it possible to process the data on the site already to such a degree that the sounding crew knows whether the sounding is proceeding satisfactorily, and can decide how best to continue the survey work. Of particular interest is digital filtering, which is especially easy with the microcomputer, and which may be used to avoid specific sources of perturbation.     

Interpretation and possibilities of applying LHR frequency determined from satellite VLF measurements in middle geomagnetic latitudes

un nmu a ¶rt;u ¶rt;am ¶rt; mm u a uuuu¶rt; a () a na. m nm, u , ¶rt;um a amm mmu nmua a m m na ¶rt; mum uaum um (2uamm m f_H u na amm m f_N. uam mm n au ¶rt; amm , ¶rt;mum amu¶rt; f _N ² f _H ² u f _H ² f _N ² . a m a n¶rt;um umnmau aamumu auauu amm n u nmu a¶rt;u.     

The Equatorial Undercurrent in the central Atlantic and its relation to tropical Atlantic variability

Seasonal to interannual variations of the Equatorial Undercurrent (EUC) in the central Atlantic at 23°W are studied using shipboard observation taken during the period 1999–2011 as well as moored velocity time series covering the period May 2005–June 2011. The seasonal variations are dominated by an annual harmonic of the EUC transport and the EUC core depth (both at maximum during September), and a semiannual harmonic of the EUC core velocity (maximum during April and September). Substantial interannual variability during the period of moored observation included anomalous cold/warm equatorial Atlantic cold tongue events during 2005/2008. The easterly winds in the western equatorial Atlantic during boreal spring that represent the preconditioning of cold/warm events were strong/weak during 2005/2008 and associated with strong/weak boreal summer EUC transport. The anomalous year 2009 was instead associated with weak preconditioning and smallest EUC transport on record from January to July, but during August coldest SST anomalies in the eastern equatorial Atlantic were observed. The interannual variations of the EUC are discussed with respect to recently described variability of the tropical Atlantic Ocean.