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

Koza, J.; Rybák, J.; Gömöry, P.; Kozak, Matus; Ariste, A. López

doi:10.1007/s11207-017-1118-z

Cited by 2 publications

(1 citation statement)

References 61 publications

(79 reference statements)

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“…The peaks are separated by 0.43 Å. Despite the difficulty in separating the components in the analysis Koza et al 2017), Athay et al (1983) analysed 13 quiescent prominences observed at Sacramento Peak with the Stokes-I (Baur et al 1980) then Stokes-II (Baur et al 1981) coronagraph spectropolarimeter, and clearly established the horizontality of the prominence magnetic field, with spatial resolution in prominences. Querfeld et al (1985) obtained similar results for two quiescent prominences also observed with Stokes-II.…”

Section: Introductionmentioning

confidence: 99%

Magnetic field vector ambiguity resolution in a quiescent prominence observed on two consecutive days

Kalewicz

Bommier

2019

A&A

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Context. Magnetic field vector measurements are always ambiguous, that is, two or more field vectors are solutions of the observed polarisation.Aims. The aim of the present paper is to solve the ambiguity by comparing the ambiguous field vectors obtained in the same prominence observed on two consecutive days. The effect of the solar rotation is to modify the scattering angle of the prominence radiation, which modifies the symmetry of the ambiguous solutions. This method, which is a kind of tomography, was successfully applied in the past to the average magnetic field vector of 20 prominences observed at the Pic du Midi. The aim of the present paper is to apply this method to a prominence observed with spatial resolution at the THÉMIS telescope (European site at Izaña, Tenerife Island). Methods. The magnetic field vector is measured by interpretation of the Hanle effect observed in the He i D 3 5875.6 Å line, within the horizontal field vector hypothesis for simplicity. The ambiguity is first solved by comparing the two pairs of solutions obtained for a "big pixel" determined by averaging the observed Stokes parameters in a large region at the prominence centre. Each pixel is then disambiguated by selecting the closest solution in a propagation from the prominence centre to the prominence boundary. Results. The results previously obtained on averaged prominences are all recovered. The polarity is found to be inverse with a small angle of about −21 • between the magnetic field vector and the long axis of the filament. The magnetic field strength of about 6 G is found to slightly increase with height, as previously observed. The new result is the observed decrease with height, of the absolute value of the angle between the magnetic field vector and the long axis of the filament.Conclusions. This result is in excellent agreement with prominence magnetohydrodynamical models.

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Section: Introductionmentioning

confidence: 99%

Magnetic field vector ambiguity resolution in a quiescent prominence observed on two consecutive days

Kalewicz

Bommier

2019

A&A

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Two fluid dynamics in solar prominences

González Manrique,

Khomenko,

Collados

et al. 2024

A&A

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Solar prominences contain a significant number of neutral species. The dynamics of the ionised and neutral fluids composing the prominence plasma can be slightly different if the collisional coupling is not strong enough. The differential dynamics can be discerned by tracing line-of-sight velocities using observational techniques. Large-scale velocities can be quantified by measuring the global local and instantaneous displacement of spectral lines by the Doppler effect. Small-scale velocities leave their imprint on the width of spectral lines. In addition, these small-scale velocities can have a thermal (pure stochastic motion) nature or a non-thermal (small-scale unresolved instabilities, high-frequency waves, etc.) origin. For this work, we used one spectral line of ionised and two spectral lines of neutral elements to measure the resolved and unresolved velocities in a prominence with the aim to investigate the possible decoupling of the observed charged and neutral species. A faint prominence was observed with the German Vacuum Tower Telescope (VTT) on June 17, 2017. Time series consisting of repeated ten-position scans over the prominence were performed while simultaneously recording the intensity spectra of the 854.2 nm 656.28 nm, and 587.56 nm lines. The line-of-sight velocities and the Doppler width of the three spectral lines were determined at every spatial position and temporal moment. To make sure all spectral lines were sampling the same plasma volume, we applied selection criteria to identify locations with optically thin plasma. In addition, asymmetric or double-peaked profiles were also excluded for the analysis, since (even in an optically thin regime) they are indicative of the presence of strong velocity gradients or multiple components in the line of sight. Thus, only optically thin, symmetric, single-lobed profiles were retained for this study. As an additional reliability test of the selection criteria, we have also compared our results with optical thickness calculations. After the application of all the selection criteria, only a region close to the prominence border met all requirements. The velocities of the three spectral lines turned out to be very similar over this region, with the ionised showing velocity excursions systematically larger compared to those of the neutral lines of and at some moments. The latter was found to be much closer to each other. Most of the velocity differences were below 1 The analysis of the Doppler widths indicated that the line shows an excess of unresolved motions. We cannot establish whether these velocities are related to a different temperature of the ions or to unresolved small-scale motions due to any non-thermal mechanism. The dynamics of the ionised and neutral plasma components in the observed prominence were very close to one another. The differences found may indicate that a localised decoupling between ions and neutrals may appear at particular spatial locations or instants of time. Indications of different unresolved motions between those species have also been obtained.

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

Cited by 2 publications

References 61 publications

Magnetic field vector ambiguity resolution in a quiescent prominence observed on two consecutive days

Magnetic field vector ambiguity resolution in a quiescent prominence observed on two consecutive days

Two fluid dynamics in solar prominences

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