Do changes in coronal emission structure imply magnetic reconnection?

We examine three major possible interpretations of observed reconfigurations of coronal X-ray and XUV emitting structures on a scale comparable to the size of the structures themselves. One possibility is that little change in the large-scale magnetic field configuration is associated with the change in emission. The other two possibilities are processes by which the magnetic field structure can change.We demonstrate that large changes in visibility in X-rays or XUV lines can be associated with relatively minor changes in the coronal magnetic field by showing the behavior of magnetic interconnections between individual active regions in a complex of activity observed by the S-054 X-ray spectrographic telescope on Skylab. While the large-scale interconnections are continuously present for at least several days, individual loops in these structures are visible for only relatively short times (1 day).The two theoretical possibilities which we discuss are frozen-in motion of the fields, and field line reconnection. We emphasize that reconnection occurs in regions much smaller than telescopic resolution. Because there are no measurements of the magnetic field in the corona in projection against the disk, existing observations are generally not sufficient to show in detail howmuch reconnection has occurred.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Slowly moving disturbances in the X-ray corona

Sequences of soft X-ray pictures, taken aboard Skylab between May and November, 1973, have made it possible to detect slowly moving disturbances originating in disrupted filaments and causing subsequent brightenings of distant coronal structures. With speeds decreasing from 400 km s^-1 shortly after the filament disruption to 10 km s^-1 four or five hours later, these disturbances appear to be identical with slow waves earlier inferred by Bruzek, Öhman, and Yajima from chromospheric observations.     

Das Typische Isolinien Grundfeld und Seine Anwendung (2. Teil)

Ohne Zusammenfassung     

First results of DORIS data analysis at Geodetic Observatory Pecný

In a cooperation between the Astronomical Institute, University of Bern (AIUB), the Geodetic Observatory Pecný (GOPE), and the Institut Géographique National (IGN), DORIS data analysis capabilities were implemented into a development version of the Bernese GPS software. The DORIS Doppler observables are reformulated such that they are similar to global navigation satellite system (GNSS) carrier-phase observations, allowing the use of the same observation models and algorithms as for GNSS carrier-phase data analysis with only minor software modifications. As such, the same algorithms may be used to process DORIS carrier-phase observations. First results from the analysis of 3 weeks of DORIS data (September 2004, five DORIS-equipped satellites) at GOPE are promising and are presented here. They include the comparison of station coordinates with coordinate estimates derived by the Laboratoire d’Etudes en Géophysique et Océanographie Spatiale/Collecte Localisation Satellites analysis centre (LCA) and the Institut Géographique National/Jet Propulsion Laboratory (IGN/JPL), and the comparison of Earth orientation parameters (EOPs) with the International Earth Rotation and Reference Frames Service (IERS) C04 model. The modified Bernese results are of a slightly lower, but comparable, quality than corresponding solutions routinely computed within the IDS (International DORIS Service). The weekly coordinate repeatability RMS is of the order of 2–3 cm for each 3D station coordinate. Comparison with corresponding estimates of station coordinates from current IDS analysis centers demonstrates similar precision. Daily pole component estimates show a mean difference from IERS-C04 of 0.6  mas in X _p and  ? 0.5  mas in Y _p and a RMS of 0.8  mas in X _p and 0.9  mas in Y _p (mean removed). An automatic analysis procedure is under development at GOPE, and routine DORIS data processing will be implemented in the near future.     

The definition of mesoscale selective forecast error covariances for a limited area variational analysis

Summary ?The paper deals with an alternative formulation of the so-called NMC (National Meteorological Center, now National Centers for Environmental Prediction) statistics to compute the background error covariance matrix to be used in a mesoscale variational analysis. While the standard method uses differences of forecasts valid for the same time, but starting from different analysis times, the new formulation required the recomputation of the short-term forecast with the initial and lateral boundary data that come from the long-term run. In the frame of a limited-area model, this approach forces the error variances at large scales to decrease drastically, because those scales are controlled by the (constant data) lateral boundary coupling. As a result, the background cost function acts more scale selectively, with an emphasis on medium scales. The analysis increments obtained from the 3D-VAR system show that the analysis increments are sharper and more concentrated with the new formulation, both in single observation and in full observation experiments. This work is part of a wider project for building a variational assimilation system inside the ALADIN model. The complete system should concentrate on mesoscale features and it should not reanalyse those scales that were already treated by the global model (ARPEGE). Some difficulties and perspectives are drawn in the concluding discussion. Received February 12, 2001; revised July 24, 2001     

Sensitivity of the Sharpe and Worden gravity meters to vertical motion

Summary Using the least-squares method the constants of both gravity meters — seismometers — were derived from the amplitude responses, observed under vertical motion on a vibrating table in the 0.3–30 s range. The values of the seismogram amplitudes, above which seismic waves cause an observable displacement of the gravity meter reading beam, were determined for the SKD and Press-Ewing station seismographs.     

New Towns and their environment

The environment has, ins a regional sense, the function of usefulness and the function of housing both being very often contradictory. The prospects of New Towns reduce the occurrence of such conflicts and bring some possibilities for applied-geography-intervention. In the densely populated countries of Central Europe mining, manufacturing, administrative and regional utilization are the main decisive functions in the developing for the origin, localization and prosperity of New Towns.     

Influence of atmospheric pressure variations on measurements made with Sharpe and Worden gravimeters

Summary The paper deals with the influence of the atmospheric pressure variations on Sharpe gravimeters CG 2 No. 226 and 280 and on the Worden gravimeter No. 978, equipped with a thermostat.Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday     

An analysis of the palaeomagnetic field

Summary The paper is devoted to a critical evaluation of the hypothesis of the prevalent character of the palaeomagnetic field in the course of the whole Phanerozoic. The study ties in with the synthetic processing of all so far published palaeomagnetic data for Eurasia and Africa respecting some of the models ensuing from the concept of plate tectonics. Initial material for testing the dipolar hypothesis was obtained by statistical processing of the palaeomagnetic pole positions and by analyzing the values of the so-called palaeorotation, the palaeoinclination difference and of palaeodivergence. It was shown that, by defining tectonically stable blocks (plates, palaeoplates) within the scope of the Eurasian continent and within the scope of the African continent as a whole, data were obtained bringing evidence of the predominating dipolar character of the mean geomagnetic field for the period from the Quaternary to the Cambrian, with the exception of the Silurian which has not been studied sufficiently. The deviations of the palaeomagnetic directions from the direction of the dipolar field within the scope of the stable blocks have the character of a Gaussian distribution and the standard deviations only amount to a few degrees.