Properties of Magnetic Tongues over a Solar Cycle     

Mariano?PoissonEmail author  Pascal?Démoulin  Marcelo?López Fuentes  Cristina?H.?Mandrini 《Solar physics》2016,291(6):1625-1646

The photospheric spatial distribution of the main magnetic polarities of bipolar active regions (ARs) present during their emergence deformations are known as magnetic tongues. They are attributed to the presence of twist in the toroidal magnetic-flux tubes that form the ARs. The aim of this article is to study the twist of newly emerged ARs from the evolution of magnetic tongues observed in photospheric line-of-sight magnetograms. We apply the procedure described by Poisson et al. (Solar Phys. 290, 727, 2015a) to ARs observed over the full Solar Cycle 23 and the beginning of Cycle 24. Our results show that the hemispherical rule obtained using the tongues as a proxy of the twist has a weak sign dominance (53 % in the southern hemisphere and 58 % in the northern hemisphere). By defining the variation of the tongue angle, we characterize the strength of the magnetic tongues during different phases of the AR emergence. We find that there is a tendency of the tongues to be stronger during the beginning of the emergence and to become weaker as the AR reaches its maximum magnetic flux. We compare this evolution with the emergence of a toroidal flux-rope model with non-uniform twist. The variety of evolution of the tongues in the analyzed ARs can only be reproduced when using a broad range of twist profiles, in particular having a large variety of twist gradients in the direction vertical to the photosphere. Although the analytical model used is a special case, selected to minimize the complexity of the problem, the results obtained set new observational constraints to theoretical models of flux-rope emergence that form bipolar ARs.  相似文献   

Zooplankton and forage fish species off Peru: Large-scale bottom-up forcing and local-scale depletion   总被引：6，自引：5，他引：1  

Patricia Ayn  Gordon Swartzman  Arnaud Bertrand  Mariano Gutirrez  Sophie Bertrand 《Progress in Oceanography》2008,79(2-4):208

The Humboldt Current System, like all upwelling systems, has dramatic quantities of plankton-feeding fish, which suggested that their population dynamics may ‘drive’ or ‘control’ ecosystem dynamics. With this in mind we analysed the relationship between forage fish populations and their main prey, zooplankton populations. Our study combined a zooplankton sampling program (1961–2005) with simultaneous acoustic observations on fish from 40 pelagic surveys (1983–2005) conducted by the Peruvian Marine Research Institute (IMARPE) and landing statistics for anchoveta (Engraulis ringens) and sardine (Sardinops sagax) along the Peruvian coast from 1961 to 2005. The multi-year trend of anchoveta population abundance varied consistently with zooplankton biovolume trend, suggesting bottom-up control on anchovy at the population scale (since oceanographic conditions and phytoplankton production support the changes in zooplankton abundance). For a finer-scale analysis (km) we statistically modelled zooplankton biovolume as a function of geographical (latitude and distance from the 200-m isobath), environmental (sea surface temperature), temporal (year, month and time-of-day) and biological (acoustic anchovy and sardine biomass within 5 km of each zooplankton sample) covariates over all survey using both classification and regression trees (CART) and generalized additive models (GAM). CART showed local anchoveta density to have the strongest effect on zooplankton biovolume, with significantly reduced levels of biovolume for higher neighbourhood anchoveta biomass. Additionally, zooplankton biovolume was higher offshore than on the shelf. GAM results corroborated the CART findings, also showing a clear diel effect on zooplankton biovolume, probably due to diel migration or daytime net avoidance. Apparently, the observed multi-year population scale bottom-up control is not inconsistent with local depletion of zooplankton when anchoveta are locally abundant, since the latter effect was observed over a wide range of overall anchoveta abundance.  相似文献   

A note on the SG(<Emphasis Type="Italic">m</Emphasis>) test     

Fernando A. López  Mariano Matilla-García  Jesús Mur  Antonio Páez  Manuel Ruiz 《Journal of Geographical Systems》2016,18(1):87-96

López et al. (Reg Sci Urban Econ 40(2–3):106–115, 2010) introduce a nonparametric test of spatial dependence, called SG(m). The test is claimed to be consistent and asymptotically Chi-square distributed. Elsinger (Reg Sci Urban Econ 43(5):838–840, 2013) raises doubts about the two properties. Using a particular counterexample, he shows that the asymptotic distribution of the SG(m) test may be far from the Chi-square family; the property of consistency is also questioned. In this note, the authors want to clarify the properties of the SG(m) test. We argue that the cause of the conflict is in the specification of the symbolization map. The discrepancies can be solved by adjusting some of the definitions made in the original paper. Moreover, we introduce a permutational bootstrapped version of the SG(m) test, which is powerful and robust to the underlying statistical assumptions. This bootstrapped version may be very useful in an applied context.  相似文献   

Population Abundances, Tidal Movement, Burrowing Ability and Oxygen Uptake of Emerita analoga (Stimpson) (Crustacea, Anomura) on a Sandy Beach of South-Central Chile     

Mariano Lastra  Eduardo Jaramillo  Jesús López  Heraldo Contreras  Cristián Duarte  & J. Germán Rodríguez 《Marine Ecology》2004,25(1):71-89

Abstract. Field sampling and other experiments were carried out during February 2001 to determine whether different morphodynamic characteristics occurring within an intermediate sandy beach of southern Chile (ca. 39°S) convey differences in population abundance, tidal movement, burrowing ability and oxygen uptake of the anomuran crab Emerita analoga (Stimpson, 1857). Crabs were collected along transects extended between the lowest swash levels and the retention zone above the effluent line of the south and north end of the beach. Burrowing times of nearly 70 crabs collected at each study site were measured in saturated sands collected from the lowest swash level of each site. Oxygen uptake of crabs was measured in incubation glass bottles. The intertidal zone of the north end of the beach was wider (56 m) and flatter (1/14) than that of the south end (45 m and 1/9, respectively). In general, the swash zone of the north end was significantly wider than the south end throughout the sampling period. The frequency of swashes and number of swash crossings above the effluent line, plus up‐wash speed, were usually higher at the steeper south end of the beach. The mean population abundance of E. analoga per linear metre of beach was significantly higher at the north end, whereas density per square metre was significantly higher at the south end. No differences were found in biomass figures. Although the highest abundance of crabs at the north end was usually observed at the lowest swash levels, similar population abundances occurred along all the tidal levels sampled at the south end. Burrowing times of crabs collected from both ends of the beach increased significantly with increasing carapace length and body mass. The mean burrowing time of crabs collected at the south end of the beach was shorter than that of those collected at the north end. Oxygen uptake of E. analoga was positively and exponentially correlated with the size of individuals collected from both ends of the beach. Results of ANCOVA showed no significant difference between the regression lines obtained for the oxygen uptake of crabs collected at both ends of the beach. It is concluded that physical features of each end of the beach seem not to differ enough to produce differences in oxygen uptake of E. analoga, or in the biomass, population structure and body size of crabs, within a single beach of south‐central Chile.  相似文献   

Recruitment indices of European hake, Merluccius merluccius (Linnaeus 1758), in the Northwest Mediterranean based on landings from bottom-trawl multispecies fisheries     

Goni  Raquel; Adlerstein  Sara; Alvarez  Federico; Garcia  Mariano; Sanchez  Pilar; Sbrana  Mario; Maynou  Francesc; Viva  Claudio 《ICES Journal of Marine Science》2004,61(5):760-773

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PIANCALDOLI METEORITE: CHEMISTRY,MINERALOGY AND PETROLOGY     

Marcello Carapezza  P. Mario Nuccio  Mariano Valenza 《Meteoritics & planetary science》1976,11(3):195-205

The fall occurred near Piancaldoli, Florence, Italy, at 19.14 U.T. on the 10th August 1968. The fireball broke up in the atmosphere producing a cloud like a balloon. The trajectory and the terminal point were calculated, leading to the recovery of three small meteoritic fragments, found on the roof of a house. Chemical analysis gave the following results: SiO₂ 40.80; TiO₂ 0.15; Al₂O₃ 2. 70; Cr₂O₃ 0.47; FeO 17.20; MnO 0.07; MgO 25.18; CaO 1.95; Na₂O 0.64; K₂O 0.07; P₂O₅ 0.20; NiS 0.93; FeS 6.24; Fe° 2.40; Ni° 0.40; Co 0.05; sum 99.45. In the lithic portion of the meteorite the following minerals were found: both clino and orthopyroxenes (En = 76 to 98%), olivines (Fo = 66 to 98%), troilite, pyrrhotite, pentlandite, kamacite, ilmenite, apatite, merillite, schreibersite, chromite and Henderson phase. From all the mineralogical and petrological data, we conclude that the Piancaldoli meteorite is an “unequilibrated ordinary chondrite,” LL3. The microbrecciated structure of the rock and some shock features were observed, while the rock as a whole is unshocked, suggesting that these features were caused by impact events which took place during the accretion of the parent body.  相似文献   

Reply to comments by G. Gambolati and G. Galeati     

Shlomo P. Neuman  Javier Samper  Mariano Hernandez 《Mathematical Geology》1987,19(3):259-266

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Moisture source in the Hyblean Mountains region (south-eastern Sicily, Italy): Evidence from stable isotopes signature     

Fausto Grassa  Rocco Favara  Mariano Valenza 《Applied Geochemistry》2006,21(12):2082-2095

Here the authors present results of an isotope study on precipitation collected during a 2-a period from a rain-gauge network consisting of 6 stations located at different elevations in the Hyblean Mountains (HM) region, in south-eastern Sicily. The slope of the local meteoric water line (δD = 6.50 δ¹⁸O + 9.87) obtained for the region suggests that precipitation is affected by evaporation during rainfall events. The main variations in rainwater isotope composition are due to seasonal effects and elevation. An average ²H excess value of +21.2‰ was found for precipitation events less affected by evaporation (i.e. when the rainfall was >65 mm/month). The spatial distribution of O isotope composition of precipitation shows a negative gradient from east and south to the inner areas. The depositional rate of Cl, used as a tracer of the origin of air masses, is highest at the coastal rain-gauges (SR and MRG stations) and lowest on the northern flank of the HM region (SC station). Based on these findings, a model is proposed for the origin of precipitation in the HM region, which assumes that a Mediterranean-derived component is the main source of moisture in the studied area. D/H and ¹⁸O/¹⁶O ratios of inferred meteoric recharge waters were also compared with the isotope composition of waters collected from the main local springs and wells. The best linear fit of the δ¹⁸O vs δD relationship for Hyblean groundwater is δD = 4.85 δ¹⁸O–2.01. The enrichment of heavy isotopes in Hyblean groundwater is probably due to evaporation occurring after precipitation events or to a recharging contribution from surface waters (lakes or rivers) enriched in heavy isotopes.  相似文献   

Heat-producing Elements-enriched Continental Mantle Lithosphere and Proterozoic Intracontinental Orogens: Insights from Brasiliano/Pan-African Belts     

Srgio Pacheco Neves  Gorki Mariano 《Gondwana Research》2004,7(2):427-436

Collisional and accretionary processes have been recognized in several Precambrian orogens, but the formation of intracontinental (ensialic) orogens has remained elusive. The recognition that modern orogenic belts (as, for example, the mountain belts of central Asia) may form in response to far-field stresses transmitted to the interior of continental plates removed much of the objection against Proterozoic intracontinental deformation. However, the causes responsible for the localization of contractional deformation are still uncertain. Due to the strong dependence of lithosphere rheology on temperature, lithospheric thermal weakening prior to contraction must be a required condition. Studies of dioritic rocks from Borborema Province, northeastern Brazil, and Damara belt, southern Africa, indicate that they are derived from ancient, incompatible elements-enriched subcontinental lithosphere. The concentrations of the heat-producing elements K (0.6 wt %), U (0.02–0.2 ppm) and Th (0.15–1.5 ppm) estimated for this source allow calculations of heat production between 0.09 and 0.25 mW m⁻³. These high values of heat generation may cause increases in temperature of several tens to three hundred degrees Celsius with respect to cratonic mantle lithosphere, leading to great reductions in lithosphere strength. Consequently, continental domains underlain by hot and weak continental mantle may thicken under the action of relatively feeble tectonic forces. High rheological contrasts between these domains and adjacent stiff and cold blocks provide an explanation for formation of intracontinental orogens.  相似文献   

Fault-controlled Soil CO2 Degassing and Shallow Magma Bodies: Summit and Lower East Rift of Kilauea Volcano (Hawaii), 1997     

Salvatore Giammanco  Sergio Gurrieri  Mariano Valenza 《Pure and Applied Geophysics》2006,163(4):853-867

Soil CO₂ flux measurements were carried out along traverses across mapped faults and eruptive fissures on the summit and the lower East Rift Zone of Kilauea volcano. Anomalous levels of soil degassing were found for 44 of the tectonic structures and 47 of the eruptive fissures intercepted by the surveyed profiles. This result contrasts with what was recently observed on Mt. Etna, where most of the surveyed faults were associated with anomalous soil degassing. The difference is probably related to the differences in the state of activity at the time when soil gas measurements were made: Kilauea was erupting, whereas Mt. Etna was quiescent although in a pre-eruptive stage. Unlike Mt. Etna, flank degassing on Kilauea is restricted to the tectonic and volcanic structures directly connected to the magma reservoir feeding the ongoing East Rift eruption or in areas of the Lower East Rift where other shallow, likely independent reservoirs are postulated. Anomalous soil degassing was also found in areas without surface evidence of faults, thus suggesting the possibility of previously unknown structures. Received: November 2003, revised: January 2005, accepted: January 2005  相似文献