Magnetic source regions of coronal mass ejections

The majority of flare activity arises in active regions which contain sunspots, while Coronal Mass Ejection (CME) activity can also originate from decaying active regions and even so-called quiet solar regions which contain a filament. Two classes of CME, namely flare-related CME events and CMEs associated with filament eruption are well reflected in the evolution of active regions. The presence of significant magnetic stresses in the source region is a necessary condition for CME. In young active regions magnetic stresses are increased mainly by twisted magnetic flux emergence and the resulting magnetic footpoint motions. In old, decayed active regions twist can be redistributed through cancellation events. All the CMEs are, nevertheless, caused by loss of equilibrium of the magnetic structure. With observational examples we show that the association of CME, flare and filament eruption depends on the characteristics of the source regions:

?the strength of the magnetic field, the amount of possible free energy storage,

?the small- and large-scale magnetic topology of the source region as well as its evolution (new flux emergence, photospheric motions, cancelling flux), and

?the mass loading of the configuration (effect of gravity). These examples are discussed in the framework of theoretical models.

     

The influence of recultivation technique and seed mixture on erosion stability after restoration in mountain environment

Control of erosion, and all of its after effects, from increased surface drainage and erosion to the formation of karst, is one of the essential problems when undertaking recultivation following necessary interventions in the sub-alpine and alpine vegetation stage (high zones). Average slope inclinations of 30–45% in the vicinity of ski runs, and far above in areas of natural erosion and avalanche zones, make restoration processes with sufficient erosion protection the prerequisite for success. Only a sufficient vegetation development of more than 70% ground cover stabilises the topsoil in the long term and reduces soil erosion to an acceptable degree. From 1999 to 2002, an international EU project with the participation of research groups and private firms from Austria, Italy and Germany was carried out under the direction of the Agricultural Research and Education Centre Raumberg-Gumpenstein (AREC) on five different Alpine sites at altitudes from 1,245 to 2,350 m above sea level. The aim of the work was the formulation of practice-relevant requirements for recultivation following intervention in high zones, especially following constructional measures in the vicinity of ski runs and lifts, torrent- and avalanche barriers. In a statistical comparison, the relationship between restoration techniques, seed mixtures of differing ecological value and vegetation cover was observed. The influence of application technique on erosion processes after restoration was obvious for the first two vegetation periods. Only with the additional use of mulch covers could increase surface drainage and noticeable soil loss be avoided. At high altitudes, the choice of seed mixture, irrespective of whether rapid or slow growing and independent of the extent of accompanying fertilisation, had no significance in the first two vegetation periods following sowing. In the following growing seasons, however, higher cover values were obtained with site-specific seed mixtures at three of the five experimental sites. While few species of the commercial seed mixture showed satisfactory persistency, most of the grasses and in particular the alpine leguminosae of site-specific seed mixtures increased their share during the observation period. In the long-term, sufficient protection against erosion is only guaranteed by the use of stable, enduring and ecologically adapted species.     

Chronostratigraphy and paleoclimatic meaning of cryogenic deformations in the Central European loess

Cryoturbations in loess reflect cold and wet environments but not necessarily permafrost. Only flat bottomed cryoturbations are indicative of it. Outside the permafrost zone they occur during the wet period of the last glaciation: during the early Weichselian, the lower pleniglacial, the end of the middle pleniglacial and the late glacial. Their morphology ist related to the frost susceptibility of the superimposed layers, expressed in form of differential frost heaving, ruled by the drainage quality and the frost susceptibility gradient. Their diagenesis is discussed.     

Correlation of the Quaternary terrace sequence in the Lower Rhine valley and northern Alpine foothills of central Europe

Thirteen glacial terraces are known from the western part of the northern Alpine foothills between the Lech and Iller Rivers. In the Lower Rhine region of West Germany, a similar number of terraces are capped by interglacial floodloams and soils. Whereas the environment during individual interglaciations did not differ substantially, the glaciations were progressively more severe. The Main Terrace system of the Rhine may be an exception. The duration of the Quaternary, starting at the base of Praetiglian, is estimated at approximately 2 million yr by paleomagnetic dating. The major cold-warm climatic cycles of the earliest Pleistocene lasted approximately 100,000 yr, the same as those of the Brunhes Chron. The intervening Main Terrace system has not yet been climatically subdivided. Correlation with the Netherlands is possible because of an abundance of paleobotanic and paleomagnetic evidence. In the Alpine foothills, stratigraphically useful indicators of warm climates are missing, but analogies in terrace development permit comparison with the Lower Rhine and Danube. The terrace sequence in the Alpine foothills is incomplete, as are those along most of the other rivers in Europe. Some of the older terraces may have been eroded.     

Non-destructive estimation of potato leaf chlorophyll from canopy hyperspectral reflectance using the inverted PROSAIL model

Optimizing nitrogen (N) fertilization in crop production by in-season measurements of crop N status may improve fertilizer N use efficiency. Hyperspectral measurements may be used to assess crop N status by estimating leaf chlorophyll content. This study evaluated the ability of the PROSAIL canopy-level reflectance model to predict leaf chlorophyll content. Trials were conducted with two potato cultivars under different N fertility rates (0–300 kg N ha⁻¹). Canopy reflectance, leaf area index (LAI) and leaf chlorophyll and N contents were measured. The PROSAIL model was able to predict leaf chlorophyll content with reasonable accuracy later in the growing season. The low estimation accuracy earlier in the growing season could be due to model sensitivity to non-homogenous canopy architecture and soil background interference before full canopy closure. Canopy chlorophyll content (leaf chlorophyll content × LAI) was predicted less accurately than leaf chlrophyll content due to the low estimation accuracy of LAI for values higher than 4.5.     

Structures caused by repeated freezing and thawing in various loamy sediments: A comparison of active,fossil and experimental data

In this paper, the authors present the results of both macroscopic and microscopic investigations on structure development created by repeated ice lensing in various loamy experiments. Experimental data are compared with observations performed on active forms in High Arctic and Alpine Mountain environments. Those observations are also compared with phenomena observed in fossil periglacial formations of Western Europe. Platy and short prismatic structure formation is bonded to the hydraulic and thermal conditions during ice segregation. When a long series of alternating freezing and thawing affects platy structures, the fabric evolves, also being influenced by slope and drainage conditions: cryoturbations, frostcreep, and gelifluction can appear. They are characterized by specific microfabrics which are better developed with an increasing number of cycles: this is clear in experiments where hydraulic and thermal parameters are better controlled. Vesicles are also a prominent characteristic of the surface horizon in experiments and arctic soils. The genesis of vesicles is discussed on the basis of new observations and is related to the mechanical collapse of frost-created aggregates under the mechanical work of soil air escape during soil saturation by water at thaw.     

Geometric characteristics and evolution of a tidal channel network in experimental setting

This paper reports on a laboratory study that aims to reproduce a tidal channel network, in order to enhance the understanding of the morphodynamic evolution of the channel characteristics as the network expands and finally reaches equilibrium. A high‐resolution laser system scanned the bed topography at different time steps creating multiple digital elevation models of the channel network. Two hundred and seventy individual channel segments are analyzed and cross‐correlated in terms of their width, depth and length. The laboratory results show positive linear correlations between depth and width as well as between length and width of channel segments of the network configuration at final equilibrium. In a downstream direction, channels appear to widen more than they deepen, indirectly a sign that discharge has a stronger control on channel width than on depth. In contrast to fluvial drainage networks that commonly display fractal and scale‐invariant behavior, the geometric properties of the experimental tidal creek network shows scale dependence. Channel attributes exhibit consistent patterns of exponentially decreasing abundance, with increasing creek length, depth and width. The nature of the observed exponential distributions within creek attributes (width, depth, length) allows for statistical predictability of relative creek attribute dimensions downstream and through time. Copyright © 2010 John Wiley & Sons, Ltd.