Spatial positions of fast-time structures of a solar burst observed at 48 GHz     

E. Correia  J. E. R. Costa  P. Kaufmann  A. Magun  R. Herrmann 《Solar physics》1995,159(1):143-155

The impulsive solar burst of October 28, 1992 showed temporal and spatial fine structures that were observed at 48 GHz with the multi-beam antenna of the Itapetinga Radio Observatory. The relative positions of burst centroids were determined with a spatial accuracy of 2, with a temporal resolution of 1 millisecond. The burst intensity time profile shows fast pulses of about one second duration, superimposed by subsecond time structures. The spatial analysis of the fast pulses suggests that the emission originated from distinct locations, separated by about 5. Our results favour the idea that impulsive solar bursts are a superposition of small elementary events spread both in time and space, probably resulting from discontinuous energy release processes.  相似文献   

Impact of sampling depth and plant species on local environmental conditions, microbiological parameters and bacterial composition in a mercury contaminated salt marsh     

Cleary DF  Oliveira V  Gomes NC  Pereira A  Henriques I  Marques B  Almeida A  Cunha A  Correia A  Lillebø AI 《Marine pollution bulletin》2012,64(2):263-271

We compare the environmental characteristics and bacterial communities associated with two rushes, Juncus maritimus and Bolboschoenus maritimus, and adjacent unvegetated habitat in a salt marsh subjected to historical mercury pollution. Mercury content was higher in vegetated than unvegetated habitat and increased with sampling depth. There was also a significant relationship between mercury concentration and bacterial composition. Habitat (Juncus, Bolboschoenus or unvegetated), sample depth, and the interaction between both, however, explained most of the variation in composition (~70%). Variation in composition with depth was most prominent for the unvegetated habitat, followed by Juncus, but more constrained for Bolboschoenus habitat. This constraint may be indicative of a strong plant-microbe ecophysiological adaptation. Vegetated habitat contained distinct bacterial communities associated with higher potential activity of aminopeptidase, β-glucosidase and arylsulphatase and incorporation rates of (14)C-glucose and (14)C-acetate. Communities in unvegetated habitat were, in contrast, associated with both higher pH and proportion of sulphate reducing bacteria.  相似文献   

Plant root traits affecting the resistance of soils to concentrated flow erosion   总被引：5，自引：0，他引：5  

Melanie Burylo  Freddy Rey  Nicolle Mathys  Thierry Dutoit 《地球表面变化过程与地形》2012,37(14):1463-1470

The effect of plant species on erosion processes may be decisive for long‐term soil protection in degraded ecosystems. The identification of functional effect traits that predict species ability for erosion control would be of great interest for ecological restoration purposes. Flume experiments were carried out to investigate the effect of the root systems of three species having contrasted ecological requirements from eroded marly lands of the French Southern Alps [i.e. Robinia pseudo acacia (tree), Pinus nigra austriaca (tree) and Achnatherum calamagrostis (grass)], on concentrated flow erosion rates. Ten functional traits, describing plant morphological and biomechanical features, were measured on each tested sample. Analyses were performed to identify traits that determine plant root effects on erosion control. Erosion rates were lowest for samples of Robinia pseudo acacia, intermediate in Achnatherum calamagrostis and highest in Pinus nigra austriaca. The three species also differed strongly in their traits. Principal components analysis showed that the erosion‐reducing potential of plant species was negatively correlated to root diameter and positively correlated to the percentage of fine roots. The results highlighted the role of small flexible roots in root reinforcement processes, and suggested the importance of high root surface and higher tensile strength for soil stabilization. By combining flume experiment to plant functional traits measurements, we identified root system features influencing plant species performance for soil protection against concentrated flow erosion. Plant functional traits related to species efficiency for erosion control represent useful tools to improve the diagnosis of land vulnerability to erosion, plant community resistance and the prediction of ecosystem functioning after ecological restoration. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Time‐lapse video observation of erosion processes on the Black Marls badlands in the Southern Alps,France     

Takao Yamakoshi  Nicolle Mathys  Sébastien Klotz 《地球表面变化过程与地形》2009,34(2):314-318

In order to clarify the erosion processes on a marly bare slope in the Southern Alps, the erosion processes in a steep and erodible slope composed of the Black Marls Formation were observed by a time‐lapse video camera. The observations revealed that miniature debris flows (MDFs) occurred at the time of the rainfall‐runoff event in which the most severe erosion took place in the whole observation period of 3 months. Analysis of the camera images showed some characteristics of the MDFs, and these are discussed in the context of real rainfall‐runoff phenomena observed at the outlet of a small experimental basin including the visually observed slope. The following results were obtained. (1) A rough estimation of the total amount of sediment discharge by the MDFs showed that it was not negligible quantitatively. (2) The MDFs occurred only during the rising limb of the hydrograph during 6 minutes. (3) Based on this observation and a review of the literature, in a very steep and highly erodible slope, MDFs or similar phenomena might play an important role in the erosion and transport processes. Copyright © 2008 John Wiley and Sons, Ltd.  相似文献   

On the rotation of co-orbital bodies in eccentric orbits     

A. Leleu  P. Robutel  A. C. M. Correia 《Celestial Mechanics and Dynamical Astronomy》2016,125(2):223-246

We investigate the resonant rotation of co-orbital bodies in eccentric and planar orbits. We develop a simple analytical model to study the impact of the eccentricity and orbital perturbations on the spin dynamics. This model is relevant in the entire domain of horseshoe and tadpole orbit, for moderate eccentricities. We show that there are three different families of spin–orbit resonances, one depending on the eccentricity, one depending on the orbital libration frequency, and another depending on the pericenter’s dynamics. We can estimate the width and the location of the different resonant islands in the phase space, predicting which are the more likely to capture the spin of the rotating body. In some regions of the phase space the resonant islands may overlap, giving rise to chaotic rotation.  相似文献   

35 Seasons of U.S. Antarctic Meteorites: A Pictorial Guide to the Collection,edited by K. Righter,C. M. Corrigan,T. J. McCoy and R. P. Harvey. Hoboken,New Jersey: Wiley, 2014, 320 p. $99.95, hardcover (ISBN #978‐1‐118‐79832‐4).          下载免费PDF全文

Nicolle E. B. Zellner 《Meteoritics & planetary science》2015,50(12):2140-2141

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Solar–terrestrial,ionospheric and natural phenomena studies using the South America VLF network (SAVNET)     

Jean-Pierre Raulin  Fernando C.P. Bertoni  Pierre Kaufmann  Hernan R. Gavilán  Emilia Correia  Rubens Hadano  Nelson J. Schuch 《Journal of Atmospheric and Solar》2011,73(11-12):1581-1586

The South America VLF Network (SAVNET) has been installed in April 2009, and is composed of eight tracking receivers spread over South America, in Brazil, Peru and Argentina, and the Antarctica Peninsula. SAVNET is monitoring the properties of subionospheric propagating waves that reveal changes of the electrical properties of the ionospheric diurnal D-region or nocturnal E-region. In this paper, we will show the ability of the diagnostic obtained by SAVNET to discuss the monitoring of the solar activity on short timescales related to ionization due to solar flares. The sensitivity of flare detection as a function of the solar activity level will be discussed. On longer timescales related to the solar cycle, SAVNET is also able to provide information on the solar Lyman-α radiation. Finally we show that the VLF technique is well suited to search for of seismic-electromagnetic effects, and to provide a genuine diagnostic of high-energy astrophysical phenomena.  相似文献   

Climatology of summer midtropospheric perturbations in the U.S. northern plains. Part I: influence on northwest flow severe weather outbreaks     

Shih-Yu Wang  Tsing-Chang Chen  James Correia Jr. 《Climate Dynamics》2011,36(3-4):793-810

Northwest flow severe weather outbreaks (NWF outbreaks) describe a type of summer convective storm that occurs in areas of mid-level NWF in the central United States. Convective storms associated with NWF outbreaks often travel a long distance systematically along a northwest-southeast oriented track across the northern plains. Previous studies have observed that these migrating convective storms are frequently coupled with subsynoptic-scale midtropospheric perturbations (MPs) initiated over the Rocky Mountains. This study traces MPs for the decade of 1997–2006 using the North American Regional Reanalysis to examine their climatology and possible influence on NWF outbreaks. MPs are characterized by a well organized divergent circulation with persistent ascending motion at the leading edge promoting convection. The divergent circulation is further enhanced by low-level convergence along the northern terminus of the Great Plains low-level jet. The downstream propagation of MPs assists in forming the progressive feature of the associated convective storms. MPs have a maximum frequency in July, consistent with NWF outbreaks. In July and August, the fully developed North American anticyclone produces prevailing NWF over the northern plains, where up to 60% of rainfall and storm reports are linked to MPs. The movement, timing and rainfall distribution of MPs remarkably resemble those of NWF outbreaks. When encountering strong low-level jets, ascending motion and convergence of water vapor flux associated with MPs intensify considerably and precipitation is greatly enhanced. It is likely that NWF outbreaks are generated whenever MPs occur in association with strong low-level jets.  相似文献   

Unusual Emissions at Various Energies Prior to the Impulsive Phase of the Large Solar Flare and Coronal Mass Ejection of 4 November 2003     

Pierre Kaufmann  Gordon D. Holman  Yang Su  C. Guillermo Gimenez de?Castro  Emilia Correia  Luis O. T. Fernandes  Rodney V. de Souza  Adolfo Marun  Pablo Pereyra 《Solar physics》2012,279(2):465-475

The GOES X28 flare of 4 November 2003 was the largest ever recorded in its class. It produced the first evidence for two spectrally separated emission components, one at microwaves and the other in the THz range of frequencies. We analyzed the pre-flare phase of this large flare, twenty?minutes before the onset of the major impulsive burst. This period is characterized by unusual activity in X-rays, sub-THz frequencies, H??, and microwaves. The CME onset occurred before the onset of the large burst by about 6?min. It was preceded by pulsations of 3??C?5?s periods at sub-THz frequencies together with X-ray and microwave enhancements. The sub-THz pulsations faded out as impulsive bursts were detected at 100??C?300?keV and 7?GHz, close to the time of the first H?? brightening and the CME onset. The activities detected prior to and at the CME onset were located nearly 2?arcmin south of the following large flare, suggesting they were separate events. This unusual activity brings new clues to understanding the complex energy buildup mechanisms prior to the CME onset, occurring at a distinct location and well before the major flare that exploded afterwards.  相似文献   

Wavelet Decomposition of Submillimeter Solar Radio Bursts     

Makhmutov  V.S.  Raulin  J.-P.  Giménez de Castro  C.G.  Kaufmann  P.  Correia  E. 《Solar physics》2003,218(1-2):211-220

We present the results of wavelet decomposition of fast-time structures during four solar flares observed by the Solar Submillimeter-wave Telescope at 212 GHz. The result of the analysis shows (1) observational evidence on the existence of submm-emission time variations in the range from a few tens of millisecond up to few seconds during solar flares, and (2) that when a solar flare is in progress the time scales reduce as the bulk of the emission flux time variations is increasing.  相似文献