Vector magnetic fields in prominences     

R. Grant Athay  Charles W. Querfeld  Raymond N. Smartt  Egidio Landi Degl'innocenti  Veronique Bommier 《Solar physics》1983,89(1):3-30

Observations of linear polarization in two resolved components of HeI D₃ are interpreted using the Hanle effect to determine vector magnetic fields in thirteen prominences. As in all vector magnetic field measurements, there is a two-fold ambiguity in field direction that is symmetric to a 180° rotation about the line-of-sight. The polar angles of the fields show a pronounced preference to be close to 90° from the local solar radius, i.e., the field direction is close to horizontal. Azimuth angles show internal consistency from point to point in a given prominences, but because of the rotational symmetry, the fields may be interpreted, in most cases, as crossing the prominence either in the same sense as the underlying photospheric fields or in the opposite sense. An exceptionally well observed large prominence of approximately planar geometry exhibits no measurable change in the vector magnetic field either with height or with location along the prominence axis. A second well observed large prominence overlying a sharply curved magnetic neutral line, when interpreted assuming that the prominence field has the same sense as the photospheric field, shows a rotation in the azimuth angle of the field relative to the observer by about 150° and relative to the local plane of the prominence by about 65°. In the alternative interpretation in which the prominence field has the opposite sense of the photospheric field, the field still rotates by 150° relative to the observer but remains essentially constant with respect to the plane of the prominence. This prominence erupted shortly after the extended observations. One good quality observation during the course of the eruption gives a vector field fully consistent with the pre-eruption field in the same segment of the prominence.  相似文献   

Thermodynamical properties of unresolved magnetic flux tubes     

Egidio Landi Degl'Innocenti  Marco Landolfi 《Solar physics》1982,77(1-2):13-26

We propose a diagnostic method, based on the observation of circular polarization signals in line pairs, to derive the thermodynamical properties of unresolved magnetic elements in the solar atmosphere. The concept of response function for the ratio of circular polarization signals in two lines is introduced and its main properties are analyzed. Some detailed calculations for suitably selected line pairs are presented.  相似文献   

Probing the nature of IGR J16493−4348: spectral and temporal analysis of the 1–100 keV emission     

A. B. Hill  A. J. Dean  R. Landi  V. A. McBride  A. De Rosa  A. J. Bird  A. Bazzano  V. Sguera 《Monthly notices of the Royal Astronomical Society》2008,385(1):423-429

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Heavy metal distribution in sediments from the gulf of Catania (Italy)     

Antonino Castagna  Felice Sarro  Fulvia Sinatra  Egidio Console 《Marine pollution bulletin》1982,13(12):432-434

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On the solution of the radiative transfer equations for polarized radiation     

E. Landi Degl'innocenti  M. Landi Degl'innocenti 《Solar physics》1985,97(2):239-250

A general formalism is presented to obtain an analytical solution of the radiative transfer equations for polarized radiation when the absorption Mueller matrix for the Stokes parameters is constant along the ray-path. The formalism is then applied to find an analytical approximation of the Stokes parameters profiles for a typical chromospheric line having an optical-depth dependence of the source function of the form S() = ( + )^1/2(1 + )^1/2.  相似文献   

基于MapObjects组件的海岸带地理信息系统开发最佳技术   总被引：1，自引：0，他引：1  

胥可辉  孙效功  刘展  冯兰娣 《中国海洋大学学报(自然科学版)》2002,32(5):770-776

本文采用组件式 GIS软件 Map Objects2 .1和编程工具 Visual Basic6 .0对海岸带地理信息系统的开发思路、对象类型、系统结构和主要功能等做出讨论 ,并对海岸带地区的矢量与栅格数据在 Map Objects2 .1中的配准以及编程方法等进行分析。结果表明 ,Map Objects2 .1由于其灵活、高效、独立性强、兼容性强等特点可以有效管理海岸带数据 ,为海岸带管理提供有力的支撑  相似文献   

Complete determination of the magnetic field vector and of the electron density in 14 prominences from linear polarizaton measurements in the HeI D3 and Hα lines     

Véronique Bommier  Egidio Landi Degl'Innocenti  Jean-Louis Leroy  Sylvie Sahal-Bréchot 《Solar physics》1994,154(2):231-260

The present paper is devoted to the interpretation of linear polarization data obtained in 14 quiescent prominences with the Pic-du-Midi coronagraph-polarimeter by J. L. Leroy, in the two lines Hei D₃ andH quasi-simultaneously. The linear polarization of the lines is due to scattering of the anisotropic photospheric radiation, modified by the Hanle effect due to the local magnetic field. The interpretation of the polarization data in the two lines is able to provide the 3 components of the magnetic field vector, and one extra parameter, namely the electron density, because the linear polarization of H is also sensitive to the depolarizing effect of collisions with the electrons and protons of the medium. Moreover, by using two lines with different optical thicknesses, namely Hei D₃, which is optically thin, and H, which is optically thick ( = 1), it is possible to solve the fundamental ambiguity, each line providing two field vector solutions that are symmetrical in direction with respect to the line of sight in the case of the optically thin line, and which have a different symmetry in the case of the optically thick line.It is then possible to determine without ambiguity the polarity of the prominence magnetic field with respect to that of the photospheric field: 12 prominences are found to be Inverse polarity prominences, whereas 2 prominences are found to be Normal polarity prominences. It must be noticed that in 12 of the 14 cases, the line-of-sight component of the magnetic field vector has a Normal polarity (to the extent that the notion of polarity of a vector component is meaningful; no polarity can be derived in the 2 remaining cases); this may explain the controversy between the results obtained with methods based on the Hanle effect with results obtained through the Zeeman effect. A dip of the magnetic field lines across the prominence has been assumed, to which the optically thick H line is sensitive, and the optically thin Hei D₃ line is insensitive.For the Inverse prominences, the average field strength is 7.5±1.2 G, the average angle,, between the field vector and the prominence long axis is 36° ± 15°, the average angle, , between the outgoing field lines and the solar surface at the prominence boundary is 29° ± 20°, and the average electron density is 2.1 × 10¹⁰ ± 0.7 × 10¹⁰ cm^–3. For the Normal prominences, the average field strength is 13.2±2.0 G, the average angle,, between the field vector and the prominence long axis is 53° ± 15°, the average angle, , between the outgoing field lines and the solar surface at the prominence boundary is 0° ± 20° (horizontal field), and the average electron density is 8.7 × 10⁹ ± 3.0 × 10⁹ cm^–3.  相似文献   

Correction to: CrystalMom: a new model for the evolution of crystal size distributions in magmas with the quadrature-based method of moments     

Simone?ColucciEmail authorView author&#;s OrcID profile  Mattia?de’?Michieli Vitturi  Patrizia?Landi 《Contributions to Mineralogy and Petrology》2018,173(4):32

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A two‐step direct method for estimating the seismic response of nonlinear structures equipped with nonlinear viscous dampers          下载免费PDF全文

Luca Landi  Omar Fabbri  Pier Paolo Diotallevi 《地震工程与结构动力学》2014,43(11):1641-1659

The insertion of fluid viscous dampers in building structures is an innovative technology that can improve significantly the seismic response. These devices could be very useful also in the retrofit of existing buildings. The effect of this typology of damping system is usually identified with an equivalent supplemental damping ratio, which depends on the maximum displacement of the structure, so that iterative procedures are required. In this paper, a simplified direct assessment method for nonlinear structures equipped with nonlinear fluid viscous dampers is proposed. The method proposed in this study is composed by two steps. The first one yields the direct estimate of the supplemental damping ratio provided by nonlinear viscous dampers in presence of a linear elastic structural response. The second step extends the procedure to structures with nonlinear behavior. Both graphical and analytical approaches have been developed. The proposed method has then been verified through several applications and comparisons with nonlinear dynamic analyses. Moreover, an investigation has been performed with regard to the influence of the relations that define the damping reduction factor and the hysteretic damping. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Magnetic and Velocity Shear Driven Instabilities in the Heliospheric Plasma     

L. Bettarini  S. Landi  M. Velli  P. Londrillo 《Earth, Moon, and Planets》2009,104(1-4):135-137

We have addressed the problem of combined magnetic and velocity shear driven instabilities in the context of the heliospheric plasma. New high-order numerical methods have been used to analyze the instability dynamics of the heliospheric current-sheet interacting with the structure determined by the slow component of the solar wind on the solar equatorial plane above the helmet streamers. Preliminary results are presented.  相似文献