Conductive flux in the chromosphere derived from line linear polarization observation     

J.-C. Henoux  G. Chambe  D. Heristchi  M. Semel  B. Woodgate  D. Shine  J. Beckers 《Solar physics》1983,86(1-2):115-122

Linear polarization in two chromospheric lines (Hα and SI 1437 A) was observed in the gradual phase of solar flares. The polarized electric vector is directed towards disk center. This polarization could be due to collisional excitation of hydrogen and SI by energetic electrons beamed in the vertical direction. Direct excitation by a highly energetic beam of electrons of order 10–100 keV. is doubtful. The heat flux in the region connecting the transition zone to the high chromosphere during the gradual phase of a flare could lead to an anisotropic excitation. Selecting a function which represents the velocity distribution of electrons carrying heat flux, the relationship between conductive heat flux and linear line polarization has been computed. The application of the relationship between linear polarization and heat flux to the observed degree of polarization leads to the determination of the conductive heat flux in the high chromosphere. This conductive flux is of the order of magnitude of the total radiation loss in the chromosphere and below, which is also of the order of magnitude of the conductive flux in the transition zone.  相似文献   

Cloud filling of ocean colour and sea surface temperature remote sensing products over the Southern North Sea by the Data Interpolating Empirical Orthogonal Functions methodology     

Damien Sirjacobs  Aida Alvera-Azcárate  Alexander Barth  Geneviève Lacroix  YoungJe Park  Bouchra Nechad  Kevin Ruddick  Jean-Marie Beckers 《Journal of Sea Research》2011,65(1):114-130

Optical remote sensing data is now being used systematically for marine ecosystem applications, such as the forcing of biological models and the operational detection of harmful algae blooms. However, applications are hampered by the incompleteness of imagery and by some quality problems. The Data Interpolating Empirical Orthogonal Functions methodology (DINEOF) allows calculation of missing data in geophysical datasets without requiring a priori knowledge about statistics of the full dataset and has previously been applied to SST reconstructions. This study demonstrates the reconstruction of complete space–time information for 4 years of surface chlorophyll a (CHL), total suspended matter (TSM) and sea surface temperature (SST) over the Southern North Sea (SNS) and English Channel (EC). Optimal reconstructions were obtained when synthesising the original signal into 8 modes for MERIS CHL and into 18 modes for MERIS TSM. Despite the very high proportion of missing data (70%), the variability of original signals explained by the EOF synthesis reached 93.5% for CHL and 97.2% for TSM. For the MODIS TSM dataset, 97.5% of the original variability of the signal was synthesised into 14 modes. The MODIS SST dataset could be synthesised into 13 modes explaining 98% of the input signal variability. Validation of the method is achieved for 3 dates below 2 artificial clouds, by comparing reconstructed data with excluded input information. Complete weekly and monthly averaged climatologies, suitable for use with ecosystem models, were derived from regular daily reconstructions. Error maps associated with every reconstruction were produced according to Beckers et al. (2006). Embedded in this error calculation scheme, a methodology was implemented to produce maps of outliers, allowing identification of unusual or suspicious data points compared to the global dynamics of the dataset. Various algorithm artefacts were associated with high values in the outlier maps (undetected cloud edges, haze areas, contrails, and cloud shadows). With the production of outlier maps, the data reconstruction technique becomes also a very efficient tool for quality control of optical remote sensing data and for change detection within large databases.  相似文献   

Editorial to the Liège Colloquium Special Issue: Long-term studies in oceanography – a celebration of 50 years of science at the Liège Colloquium (1969 – 2018)     

Alvera-Azcárate  Aida  Troupin  Charles  Goosse  Hughes  McPhaden  Michael J.  Beckers  Jean-Marie 《Ocean Dynamics》2021,71(1):119-123

  相似文献   

Variational interpolation of high-frequency radar surface currents using DIVAnd     

Barth  Alexander  Troupin  Charles  Reyes  Emma  Alvera-Azcárate  Aida  Beckers  Jean-Marie  Tintoré  Joaquín 《Ocean Dynamics》2021,71(3):293-308

Ocean Dynamics - DIVAnd (Data-Interpolating Variational Analysis, in n-dimensions) is a tool to interpolate observations on a regular grid using the variational inverse method. We have extended...  相似文献   

Comparison between satellite and in situ sea surface temperature data in the Western Mediterranean Sea   总被引：1，自引：1，他引：0  

Aida Alvera-Azcárate  Charles Troupin  Alexander Barth  Jean-Marie Beckers 《Ocean Dynamics》2011,61(6):767-778

A comparison between in situ and satellite sea surface temperature (SST) is presented for the Western Mediterranean Sea during 1999. Several international databases are used to extract in situ data (World Ocean Database, MEDAR/Medatlas, Coriolis Data Center, International Council for the Exploration of the Sea and International Comprehensive Ocean-Atmosphere Data Set). The in situ data are classified into different platforms or sensors (conductivity–temperature–depth, expendable bathythermographs, drifters, bottles, and ships), in order to assess the relative accuracy of these type of data with respect to Advanced Very High Resolution Radiometer SST satellite data. It is shown that the results of the error assessment vary with the sensor type, the depth of the in situ measurements, and the database used. Ship data are the most heterogeneous data set, and therefore present the largest differences with respect to in situ data. A cold bias is detected in drifter data. The differences between satellite and in situ data are not normally distributed. However, several analysis techniques, as merging and data assimilation, usually require Gaussian-distributed errors. The statistics obtained during this study will be used in future work to merge the in situ and satellite data sets into one unique estimation of the SST.  相似文献   

A comparison of spicules in the Hα and HeII (304 Å) lines     

Olav Kjeldseth Moe  Oddbjorn Engvold  Jacques Maurice Beckers 《Solar physics》1975,40(1):65-68

  相似文献   

The intensity,velocity and magnetic structure of a sunspot region     

J. M. Beckers  E. H. Schröter 《Solar physics》1969,7(1):22-25

  相似文献   

The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission     

B. E. Woodgate  E. A. Tandberg-Hanssen  E. C. Bruner  J. M. Beckers  J. C. Brandt  W. Henze  C. L. Hyder  M. W. Kalet  P. J. Kenny  E. D. Knox  A. G. Michalitsianos  R. Rehse  R. A. Shine  H. D. Tinsley 《Solar physics》1980,65(1):73-90

The Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission spacecraft is described, including the experiment objectives, system design, performance, and modes of operation. The instrument operates in the wavelength range 1150–3600 Å with better than 2 arc sec spatial resolution, raster range 256 × 256 arc sec², and 20 mÅ spectral resolution in second order. Observations can be made with specific sets of 4 lines simultaneously, or with both sides of 2 lines simultaneously for velocity and polarization. A rotatable retarder can be inserted into the spectrometer beam for measurement of Zeeman splitting and linear polarization in the transition region and chromosphere.Currently at MMTO, University of Arizona, Tucson, Ariz. 85721, U.S.A.  相似文献   

The maximum polarization for resonance scattering     

J. M. Beckers 《Solar physics》1974,37(2):351-352

  相似文献   

The profiles of fraunhofer lines in the presence of zeeman splitting     

J. M. Beckers 《Solar physics》1969,9(2):372-386

For the case of pure absorption lines (LTE) a method is described which enables the general computation of Zeeman-split line profiles. The magnetic field vector, the Doppler shift and the line absorption coefficient is permitted to vary arbitrarily with optical depth. Elliptical birefringence (e.g., Faraday rotation) of the solar atmosphere is taken into account. Some numerical examples are given and some interesting behaviors of the line profiles are discussed.  相似文献