Solar prominence polarimetry

Wiehr, E.; Bianda, M.

doi:10.1051/0004-6361:20030668

Cited by 16 publications

(17 citation statements)

References 13 publications

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“…Table 2 also shows the percentage contribution of the Hα radiation to the total brightness emission, given by %Hα = tB Hα /(tB Th + tB Hα ). Results are in good agreement for instance with Wiehr & Bianda (2003) and Leroy et al (1984), who measured the linear polarization of Hα radiation from prominences and found it varies within a few percent. Moreover, by the examination of a CME on August 31, 2007, Mierla et al (2011 obtained a Hα contribution to the total brightness emission more than 88% with a very low polarization, less than 5%.…”

Section: Estimate Of Hα Polarized Emission From the Blobssupporting

confidence: 82%

Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona

Dolei

Бемпорад

Spadaro

2014

A&A

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In this work we study the kinematics of three small-scale (0.01 R ) blobs of chromospheric plasma falling back to the Sun after the huge eruptive event of June 7, 2011. From a study of 3D trajectories of blobs made with the Solar TErrestrial RElations Observatory (STEREO) data, we demonstrate the existence of a significant drag force acting on the blobs and calculate two drag coefficients, in the radial and tangential directions. The resulting drag coefficients C D are between 0 and 5, comparable in the two directions, making the drag force only a factor of 0.45-0.75 smaller than the gravitational force. To obtain a correct determination of electron densities in the blobs, we also demonstrate how, by combining measurements of total and polarized brightness, the Hα contribution to the white-light emission observed by the COR1 telescopes can be estimated. This component is significant for chromospheric plasma, being between 95 and 98% of the total white-light emission. Moreover, we demonstrate that the COR1 data can be employed even to estimate the Hα polarized component, which turns out to be in the order of a few percent of Hα total emission from the blobs. If the drag forces acting on small-scale blobs reported here are similar to those that play a role during the CME propagation, our results suggest that the magnetic drag should be considered even in the CME initiation modelling.

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Section: Estimate Of Hα Polarized Emission From the Blobssupporting

confidence: 82%

Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona

Dolei

Бемпорад

Spadaro

2014

A&A

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“…(We recommend a reader of Léger and Paletou (2009) to change their Figure 9 for Figure 7.21 in Léger (2008).) This compatibility of the optical thinness with the ratio of lower than 8 settles down earlier indications of nonnegligible plasma optical thickness in He i D3 expressed in House and Smartt (1982); Athay et al (1983); López Ariste and Casini (2002); Casini et al (2003); and Wiehr and Bianda (2003) in the context of the observed ratios ranging from 6 to 7.6.…”

Section: Introductionsupporting

confidence: 85%

“…In a study of eight prominences, Athay et al (1983) found the He i D3 peak intensity ratios ranging from 6.1 to 7.6. Finally, López Ariste and Casini (2002) and Wiehr and Bianda (2003) reported peak intensity ratios of 6.8 and 6, respectively. While the former two studies employed the double-Gaussian model, the method of inferring the ratios in the latter two articles is unclear.…”

Section: Spectral Characteristics Of the Double-gaussian Modelmentioning

confidence: 97%

Spectral Characteristics of the He i D3 Line in a Quiescent Prominence Observed by THEMIS

et al. 2017

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We analyze the observations of a quiescent prominence acquired by the Téléscope Heliographique pour l'Étude du Magnetisme et des Instabilités Solaires (THEMIS) in the He i 5876Å (He i D3) multiplet aiming to measure the spectral characteristics of the He i D3 profiles and to find for them an adequate fitting model. The component characteristics of the He i D3 Stokes I profiles are measured by the fitting system approximating them with a double Gaussian. This model yields an He i D3 component peak intensity ratio of 5.5 ± 0.4, which differs from the value of 8 expected in the optically thin limit. Most of the measured Doppler velocities lie in the interval ±5 km s −1 , with a standard deviation of ±1.7 km s −1 around the peak value of 0.4 km s −1 . The wide distribution of the full-width at half maximum has two maxima at 0.25Å and 0.30Å for the He i D3 blue component and two maxima at 0.22Å and 0.31Å for the red component. The width ratio of the components is 1.04 ± 0.18. We show that the double-Gaussian model systematically underestimates the blue wing intensities. To solve this problem, we invoke a two-temperature multiGaussian model, consisting of two double-Gaussians, which provides a better representation of He i D3 that is free of the wing intensity deficit. This model suggests temperatures of 11.5 kK and 91 kK, respectively, for the cool and the hot component of the target prominence. The cool and hot components of a typical He i D3 profile have component peak intensity ratios of 6.6 and 8, implying a prominence geometrical width of 17 Mm and an optical thickness of 0.3 for the cool component, while the optical thickness of the hot component is negligible. These prominence parameters seem to be realistic, suggesting the physical adequacy of the multi-Gaussian model with important implications for interpreting He i D3 spectropolarimetry by current inversion codes.

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“…They found that the average magnetic field in prominences is consistent with earlier studies (see Leroy, 1989): a mostly horizontal field with a strength of about 20 G and with the magnetic vector pointing 20 • to 30 • off the prominence axis. In addition, the map shows magnetic fields significantly stronger than average (up to 80 G) in clearly organized patches within the prominence (also see Wiehr and Bianda, 2003;Casini, 2002, 2003;López Ariste and Aulanier, 2007). It is unclear whether these structures are related to the fine structures of quiescent prominences (e.g., vertical threads).…”

Section: Measurements Of Prominence Magnetic Fieldmentioning

confidence: 81%

Physics of Solar Prominences: II—Magnetic Structure and Dynamics

et al. 2010

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Observations and models of solar prominences are reviewed. We focus on non-eruptive prominences, and describe recent progress in four areas of prominence research: (1) magnetic structure deduced from observations and models, (2) the dynamics of prominence plasmas (formation and flows), (3) Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and large-scale patterns of the filament channels in which prominences are located. Finally, several outstanding issues in prominence research are discussed, along with observations and models required to resolve them.

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Solar prominence polarimetry

Cited by 16 publications

References 13 publications

Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona

Measurements with STEREO/COR1 data of drag forces acting on small-scale blobs falling in the intermediate corona

Spectral Characteristics of the He i D3 Line in a Quiescent Prominence Observed by THEMIS

Physics of Solar Prominences: II—Magnetic Structure and Dynamics

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