UNDERSTANDING THE MG II AND H
                    <i>α</i>
                    SPECTRA IN A HIGHLY DYNAMICAL SOLAR PROMINENCE

Heinzel, P.; Schmieder, B.; Mein, N.; Gunár, S.

doi:10.1088/2041-8205/800/1/l13

Cited by 38 publications

(46 citation statements)

References 10 publications

(25 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spectroscopic analysis of the IRIS profiles of Mg ii k and h lines made by Schmieder et al (2014b) and Levens et al (2016Levens et al ( , 2017 in combination with the results of the onedimensional (1D) non-LTE modeling of Heinzel et al (2014aHeinzel et al ( , 2015 show that these two lines are relatively strong, optically thick (up to 10 3 or 10 4 ), and sensitive to Doppler brightening or dimming effects for velocities larger than 20 km s −1 . Observations show that Mg ii profiles can be unreversed (single), reversed, or composite profiles formed by the superposition of several individual Doppler-shifted single profiles emitted along a single LOS.…”

Section: Introductionmentioning

confidence: 92%

Statistical analysis of UV spectra of a quiescent prominence observed by IRIS

Jejčič

Schwartz

Heinzel

et al. 2018

A&A

Self Cite

View full text Add to dashboard Cite

Context. The paper analyzes the structure and dynamics of a quiescent prominence that occurred on October 22, 2013 and was observed by several instruments including the Interface Region Imaging Spectrograph (IRIS). Aims. We aim to determine the physical characteristics of the observed prominence using Mg ii k and h (2796 and 2803 Å) , C ii (1334 and 1336 Å), and Si iv (1394 Å) lines observed by IRIS. In addition we study the dynamical behavior of the prominence. Methods. We employed the one-dimensional non-LTE (departures from the local thermodynamic equilibrium -LTE) modeling of Mg ii lines assuming static isothermal-isobaric slabs. We selected a large grid of models with realistic input parameters expected for quiescent prominences (temperature, gas pressure, effective thickness, microturbulent velocity, height above the solar surface) and computed synthetic Mg ii lines. The method of Scargle periodograms was used to detect possible prominence oscillations. Results. We analyzed 2160 points of the observed prominence in five different sections along the slit averaged over ten pixels due to low signal to noise ratio in the C ii and Si iv lines. We computed the integrated intensity for all studied lines, while the central intensity and reversal ratio was determined only for both Mg ii and C ii 1334 lines. We plotted several correlations: time evolution of the integrated intensities and central intensities, scatter plots between all combinations of line integrated intensities, and reversal ratio as a function of integrated intensity. We also compared Mg ii observations with the models. Results show that more than two-thirds of Mg ii profiles and about one-half of C ii 1334 profiles are reversed. Profiles of Si iv are generally unreversed. The Mg ii and C ii lines are optically thick, while the Si iv line is optically thin.Conclusions. The studied prominence shows no global oscillations in the Mg ii and C ii lines. Therefore, the observed time variations are caused by random motions of fine structures with velocities up to 10 km s −1 . The observed average ratio of Mg ii k to Mg ii h line intensities can be used to determine the prominence's characteristic temperature. Certain disagreements between observed and synthetic line intensities of Mg ii lines point to the necessity of using more complex two-dimensional multi-thread modeling in the future.

show abstract

Section: Introductionmentioning

confidence: 92%

Statistical analysis of UV spectra of a quiescent prominence observed by IRIS

Jejčič

Schwartz

Heinzel

et al. 2018

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The thickness and the height of fibril was assumed according to the typical values obtained from observations. We adapted the 2D NLTE code described in Heinzel & Anzer (2001) and Heinzel et al (2015) to compute the intensity of the fibril itself that was emergent from the top surface (e.g. as seen against the disk), and we also obtained the total optical thickness of the fibril over the line profile.…”

Section: An Effect Of the Overlying Canopymentioning

confidence: 99%

Height formation of bright points observed by IRIS in Mg II line wings during flux emergence

Grubecka

Schmieder

Berlicki

et al. 2016

A&A

Self Cite

View full text Add to dashboard Cite

Context. A flux emergence in the active region AR 111850 was observed on September 24, 2013 with the Interface Region Imaging Spectrograph (IRIS). Many bright points are associated with the new emerging flux and show enhancement brightening in the UV spectra. Aims. The aim of this work is to compute the altitude formation of the compact bright points (CBs) observed in Mg II lines in the context of searching Ellerman bombs (EBs). Methods. IRIS provided two large dense rasters of spectra in Mg II h and k lines, Mg II triplet, C II and Si IV lines covering all the active region and slit jaws in the two bandpasses (1400 Å and 2796 Å) starting at 11:44 UT and 15:39 UT, and lasting 20 min each. Synthetic profiles of Mg II and Hα lines are computed with non-local thermodynamic equlibrium (NLTE) radiative transfer treatment in 1D solar atmosphere model including a hotspot region defined by three parameters: temperature, altitude, and width. Results. Within the two IRIS rasters, 74 CBs are detected in the far wings of the Mg II lines (at +/−1 Å and 3.5 Å). Around 10% of CBs have a signature in Si IV and CII. NLTE models with a hotspot located in the low atmosphere were found to fit a sample of Mg II profiles in CBs. The Hα profiles computed with these Mg II CB models are consistent with typical EB profiles observed from ground based telescopes e.g. THEMIS. A 2D NLTE modelling of fibrils (canopy) demonstrates that the Mg II line centres can be significantly affected but not the peaks and the wings of Mg II lines. Conclusions. We conclude that the bright points observed in Mg II lines can be formed in an extended domain of altitudes in the photosphere and/or the chromosphere (400 to 750 km). Our results are consistent with the theory of heating by Joule dissipation in the atmosphere produced by magnetic field reconnection during flux emergence.

show abstract

“…The importance of the PCTR in prominence modelling has been discussed by Anzer and Heinzel (1999), and its effect on various spectral lines demonstrated by e.g. Heinzel et al (2001), Labrosse and Gouttebroze (2004), Labrosse et al (2010), Heinzel et al (2015b). However, the nature of the PCTR and its relationship to the prominence and prominence fine-structure is not fully understood.…”

Section: Introductionmentioning

confidence: 99%

Solar Prominence Modelling and Plasma Diagnostics at ALMA Wavelengths

Rodger

Labrosse

2017

Sol Phys

View full text Add to dashboard Cite

Our aim is to test potential solar prominence plasma diagnostics as obtained with the new solar capability of the Atacama Large Millimeter/submillimeter Array (ALMA). We investigate the thermal and plasma diagnostic potential of ALMA for solar prominences through the computation of brightness temperatures at ALMA wavelengths. The brightness temperature, for a chosen line of sight, is calculated using the densities of electrons, hydrogen, and helium obtained from a radiative transfer code under non-local thermodynamic equilibrium (non-LTE) conditions, as well as the input internal parameters of the prominence model in consideration. Two distinct sets of prominence models were used: isothermal-isobaric fine-structure threads, and large-scale structures with radially increasing temperature distributions representing the prominence-to-corona transition region. We compute brightness temperatures over the range of wavelengths in which ALMA is capable of observing (0.32 -9.6 mm), however, we particularly focus on the bands available to solar observers in ALMA cycles 4 and 5, namely 2.6 -3.6 mm (Band 3) and 1.1 -1.4 mm (Band 6). We show how the computed brightness temperatures and optical thicknesses in our models vary with the plasma parameters (temperature and pressure) and the wavelength of observation. We then study how ALMA observables such as the ratio of brightness temperatures at two frequencies can be used to estimate the optical thickness and the emission measure for isothermal and non-isothermal prominences. From this study we conclude that for both sets of models, ALMA presents a strong thermal diagnostic capability, provided that the interpretation of observations is supported by the use of non-LTE simulation results.

show abstract

UNDERSTANDING THE MG II AND H α SPECTRA IN A HIGHLY DYNAMICAL SOLAR PROMINENCE

Cited by 38 publications

References 10 publications

Statistical analysis of UV spectra of a quiescent prominence observed by IRIS

Statistical analysis of UV spectra of a quiescent prominence observed by IRIS

Height formation of bright points observed by IRIS in Mg II line wings during flux emergence

Solar Prominence Modelling and Plasma Diagnostics at ALMA Wavelengths

Contact Info

Product

Resources

About