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41.
M. A. Schuh J. M. Banda P. N. Bernasconi R. A. Angryk P. C. H. Martens 《Solar physics》2014,289(7):2503-2524
We present a comparative evaluation for automated filament detection in Hα solar images. By using metadata produced by the Advanced Automated Filament Detection and Characterization Code (AAFDCC) module, we adapted our trainable feature recognition (TFR) module to accurately detect regions in solar images containing filaments. We first analyze the AAFDCC module’s metadata and then transform it into labeled datasets for machine-learning classification. Visualizations of data transformations and classification results are presented and accompanied by statistical findings. Our results confirm the reliable event reporting of the AAFDCC module and establishes our TFR module’s ability to effectively detect solar filaments in Hα solar images. 相似文献
42.
The unresolved corona for three active regions (ARs) above the solar limb is investigated. Intensities measured for ions formed
above 1 MK are presented as a function of height above the solar surface. The observed decrease in intensity with altitude
is found to be best fit by an exponential. Furthermore, this exponential decrease is approximately the decrease in emission
expected for a hydrostatic planar geometry atmosphere, where the scale height temperature is dependent on the dynamics of
the AR. For two of the ARs analyzed, we have found that the best-fit temperature derived from the exponential fits is consistent
with an isothermal hydrostatic unresolved corona. 相似文献
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We use an innovative research technique to analyze combined images from the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) and the Transition Region and Coronal Explorer (TRACE). We produce a high spatial and temporal resolution simulated CDS raster or “composite” map from TRACE data and use
this composite map to jointly analyze data from both instruments. We show some of the advantages of using the “composite”
map method for coronal loop studies. We investigate two postflare loop structures. We find cool material (250 000 K) concentrated
at the tips or apex of the loops. This material is found to be above its scale height and therefore not in hydrostatic equilibrium.
The exposure times of the composite map and TRACE images are used to give an estimate of another loop’s cooling time. The
contribution to the emission in the TRACE images for the spectral lines present in its narrow passband is estimated by using
the CDS spectral data and CHIANTI to derive synthetic spectra. We obtain cospatial and cotemporal data collected by both instruments
in SOHO Joint Observations Program (JOP) 146 and show how the combination of these data can be utilized to obtain more accurate
measurements of coronal plasmas than if analyzed individually.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
46.
A perturbation method is derived forr-modes in a slowly and uniformly rotating star. In contrast to previous studies, the perturbation of the gravitational potential is included in the perturbation method.On the assumption that the effects of the centrifugal force are taken into account in the equilibrium model up to the second order in the angular velocity, an eigenvalue problem of sixth-order in the radial coordinate is derived that allows one to determine the zeroth-order toroidal displacement field and the third-order term in the expansion of the eigenfrequency. Furthermore, another eigenvalue problem is derived that governs the first-order toroidal displacement field and the fourth-order term in the expansion of the eigenfrequency. This second eigenvalue problem is also of the sixth-order in the radial coordinate.It is shown that the third-order term in the expansion of the eigenfrequency is real, and that the fourth-order term is zero. 相似文献
47.
The transport of dissolved gases in the anoxic sediments of Cape Lookout Bight, North Carolina, is controlled by diffusion and bubble ebullition and exhibits a distinct seasonal cycle. Detailed seasonal profiles of CH4, N2 and 222Rn and direct gas flux measurements indicate that ebullition dominates the flux of all dissolved gases across the sediment-water interface during summer months, and is of major importance on an annual basis. Transport within the upper 6–8 cm of sediment appears to be controlled by molecular diffusion of gases. Transport at greater depths is controlled by diffusion in winter and ebullition in summer. Rn-222 profiles were used to estimate the rate of stripping of dissolved gases within the CH4 production zone (10–30 cm); rates averaged 3–5 percent per day and agreed with estimates derived from N2 profiles. As a result of summer ebullition, the sediments of the bight are never at saturation with respect to the major gases present in seawater. Evidence from other sites suggests that ebullition may be an important transport process in many coastal sediments, and may provide mechanism for the transport of volatile reduced compounds between anoxic sediments and the atmosphere. 222Rn is a useful tracer for quantifying this transport. 相似文献
48.
The release of remineralized N and P from the organic-rich anoxic sediments of Cape Lookout Bight is controlled by processes occurring within the sediment column and at the sediment-water interface. The relatively rapid rates of temperature dependent microbial degradation of organic matter support seasonally varying nutrient fluxes ranging from 20 to 1200 μmol·m?2·hr?1 for dissolved ammonium and from ? 20 to 120 μmol·m?2·hr?1 for total dissolved phosphate (measured in situ over the period October, 1976 to October, 1978). Molecular diffusion along steep vertical pore water concentration gradients measured simultaneously cannot explain the high fluxes observed during warmer months. Gradients for ammonium and phosphate ranged from 0.33 to 1.10 and from 0 to 0.29 μmol·cm?3pw·cm?1s respectively. These high summertime fluxes appear to result from increased sediment-water transport associated with bubble tubes created and maintained by low-tide methane gas bubble ebullition. When these tubes are present, apparent bulk sediment diffusivities calculated from concurrent studies of methane and radon-222 sediment-water exchange are 1.0–3.1 times greater than molecular diffusivities. Nutrient fluxes calculated via Fick's first law taking into account this enhanced transport and the differential diffusive mobilities of dissolved ammonium, phosphate and phosphate ion pairs indicate that removal by aerobic adsorption and/or biological uptake at the sediment-water interface plays an important role in controlling nutrient exchange in these sediments. 相似文献
49.
Scott G. Johnston Richard T. Bush Leigh A. Sullivan Edward D. Burton Douglas Smith Michelle A. Martens Angus E. McElnea Col R. Ahern Bernard Powell Luisa P. Stephens Steve T. Wilbraham Simon van Heel 《Estuarine, Coastal and Shelf Science》2009
This study examines the remediation of surface water quality in a severely degraded coastal acid sulfate soil landscape. The remediation strategy consisted of partial restoration of marine tidal exchange within estuarine creeks and incremental tidal inundation of acidified soils, plus strategic liming of drainage waters. Time-series water quality and climatic data collected over 5 years were analysed to assess changes in water quality due to this remediation strategy. A time-weighted rainfall function (TWR) was generated from daily rainfall data to integrate the effects of antecedent rainfall on shallow groundwater levels in a way that was relevant to acid export dynamics. Significant increases in mean pH were evident over time at multiple monitoring sites. Regression analysis at multiple sites revealed a temporal progression of change in significant relationships between mean daily electrical conductivity (EC) vs. mean daily pH, and TWR vs. mean daily pH. These data demonstrate a substantial decrease over time in the magnitude of creek acidification per given quantity of antecedent rainfall. Data also show considerable increase in soil pH (2–3 units) in formerly acidified areas subject to tidal inundation. This coincides with a decrease in soil pe, indicating stronger reducing conditions. These observations suggest a fundamental shift has occurred in sediment geochemistry in favour of proton-consuming reductive processes. Combined, these data highlight the potential effectiveness of marine tidal inundation as a landscape-scale acid sulfate soil remediation strategy. 相似文献
50.
Thijs Van der Meeren Dirk Verschuren Emi Ito Koen Martens 《Journal of Paleolimnology》2010,44(4):903-911
Quantification of intra-specific morphological variability of aquatic biota along environmental gradients can produce biological
proxies that can be applied to paleoenvironmental reconstructions. This morphology-derived proxy information can be especially
valuable when dealing with low-diversity fossil assemblages, i.e. in situations when paleoenvironmental inference based on
species composition of the assemblage is less effective. We analyzed valve size and outline shape of the widespread and highly
environmentally tolerant ostracode species Limnocythere inopinata collected in 15 lakes and ponds of Western Mongolia. We quantified shape variability among and within these living populations
in relation to water chemistry and physical habitat variables. Our results indicate that: (1) a population’s mean valve outline
is related to habitat type, (2) surface water temperature, the alkalinity to sulphate ratio, specific conductance and total
phosphorus together explain a high portion of the variance in mean valve outline between populations, and (3) a quantitative
model inferring the alkalinity to sulphate ratio from mean valve outline has an R2 of 0.88 and RMSEP of 0.17. These results
corroborate the hypothesis that high morphological variability in this ostracode species is due to both ecophenotypic variance
and high clonal diversity associated with a mixed reproductive strategy (a combination of sexual and parthenogenetically reproducing
lineages), and underline the value of morphometric techniques in paleoecology. 相似文献