Author name code: jejcic ADS astronomy entries on 2022-09-14 author:"Jejcic, Sonja" ------------------------------------------------------------------------ Title: Coronal mass ejection followed by a prominence eruption and a plasma blob as observed by Solar Orbiter Authors: Bemporad, A.; Andretta, V.; Susino, R.; Mancuso, S.; Spadaro, D.; Mierla, M.; Berghmans, D.; D'Huys, E.; Zhukov, A. N.; Talpeanu, D. -C.; Colaninno, R.; Hess, P.; Koza, J.; Jejčič, S.; Heinzel, P.; Antonucci, E.; Da Deppo, V.; Fineschi, S.; Frassati, F.; Jerse, G.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Romoli, M.; Sasso, C.; Slemer, A.; Stangalini, M.; Teriaca, L. Bibcode: 2022A&A...665A...7B Altcode: 2022arXiv220210294B Context. On 2021 February 12, two subsequent eruptions occurred above the western limb of the Sun, as seen along the Sun-Earth line. The first event was a typical slow coronal mass ejection (CME), followed ∼7 h later by a smaller and collimated prominence eruption, originating south of the CME, followed by a plasma blob. These events were observed not only by the SOHO and STEREO-A missions, but also by the suite of remote-sensing instruments on board Solar Orbiter.
Aims: We show how data acquired by the Full Sun Imager (FSI), the Metis coronagraph, and the Heliospheric Imager (HI) from the Solar Orbiter perspective can be combined to study the eruptions and different source regions. Moreover, we show how Metis data can be analyzed to provide new information about solar eruptions.
Methods: Different 3D reconstruction methods were applied to the data acquired by different spacecraft, including remote-sensing instruments on board Solar Orbiter. Images acquired by the two Metis channels in the visible light (VL) and H I Ly-α line (UV) were combined to derive physical information about the expanding plasma. The polarization ratio technique was also applied for the first time to Metis images acquired in the VL channel.
Results: The two eruptions were followed in 3D from their source region to their expansion in the intermediate corona. By combining VL and UV Metis data, the formation of a post-CME current sheet (CS) was followed for the first time in the intermediate corona. The plasma temperature gradient across a post-CME blob propagating along the CS was also measured for the first time. Application of the polarization ratio technique to Metis data shows that by combining four different polarization measurements, the errors are reduced by ∼5 − 7%. This constrains the 3D plasma distribution better.

Movies associated to Figs. 4-7 are available at https://www.aanda.org Title: Diagnostics of The Prominence Plasma Based on IRIS, H-alpha and ALMA Observations Authors: Berlicki, Arkadiusz; Bárta, Miroslav; Gunár, Stanislav; Heinzel, Petr; Jejcic, Sonja; Radziszewski, Krzysztof; Rudawy, Pawel Bibcode: 2022cosp...44.2543B Altcode: Solar prominences are now commonly observed above the solar limb in different spectral bands and recent developments of new observing techniques allow us to detect them from radio to far-UV ranges. In addition to often used spectral observations in optical and UV, ALMA interferometer obtained high-resolution images of a quiescent solar prominence at 3 millimeters (Band 3) during the coordinated space and ground-based observing campaign. For the first time high-resolution observations of such structures in the millimeter radio domain are available. The fine structures of this prominence was also observed in the UV with IRIS and in the H$\alpha$ line with the MSDP of Wroc{\l}aw Observatory. Both UV and H$\alpha$ data contains not only images, but also spectra which makes the available dataset extremely valuable. Moreover, all UV, H$\alpha$ and ALMA observations are co-temporal which gives an unprecedented opportunity for a novel diagnostic, not available so far. In this work we present analysis of the prominence spectral characteristics in H$\alpha$ and UV Mg II lines, looking for the statistical dependence between different parameters (metrics) in the line profiles. This combined data is then used for determination of plasma parameters in the prominence fine structures. In addition, UV and H$\alpha$ spectral maps are compared with the brightness temperature mosaics from ALMA, providing an additional constraint on the plasma kinetic temperature. Detailed diagnostics is then based on extensive NLTE numerical simulations of the radiative transfer inside heterogeneous prominence structures. Title: Prominence eruption observed in He II 304 Å up to >6 R⊙ by EUI/FSI aboard Solar Orbiter Authors: Mierla, M.; Zhukov, A. N.; Berghmans, D.; Parenti, S.; Auchère, F.; Heinzel, P.; Seaton, D. B.; Palmerio, E.; Jejčič, S.; Janssens, J.; Kraaikamp, E.; Nicula, B.; Long, D. M.; Hayes, L. A.; Jebaraj, I. C.; Talpeanu, D. -C.; D'Huys, E.; Dolla, L.; Gissot, S.; Magdalenić, J.; Rodriguez, L.; Shestov, S.; Stegen, K.; Verbeeck, C.; Sasso, C.; Romoli, M.; Andretta, V. Bibcode: 2022A&A...662L...5M Altcode: 2022arXiv220515214M
Aims: We report observations of a unique, large prominence eruption that was observed in the He II 304 Å passband of the Extreme Ultraviolet Imager/Full Sun Imager telescope aboard Solar Orbiter on 15-16 February 2022.
Methods: Observations from several vantage points - Solar Orbiter, the Solar-Terrestrial Relations Observatory, the Solar and Heliospheric Observatory, and Earth-orbiting satellites - were used to measure the kinematics of the erupting prominence and the associated coronal mass ejection. Three-dimensional reconstruction was used to calculate the deprojected positions and speeds of different parts of the prominence. Observations in several passbands allowed us to analyse the radiative properties of the erupting prominence.
Results: The leading parts of the erupting prominence and the leading edge of the corresponding coronal mass ejection propagate at speeds of around 1700 km s−1 and 2200 km s−1, respectively, while the trailing parts of the prominence are significantly slower (around 500 km s−1). Parts of the prominence are tracked up to heights of over 6 R⊙. The He II emission is probably produced via collisional excitation rather than scattering. Surprisingly, the brightness of a trailing feature increases with height.
Conclusions: The reported prominence is the first observed in He II 304 Å emission at such a great height (above 6 R⊙).

Movies are available at https://www.aanda.org Title: Non-LTE Inversion of Prominence Spectroscopic Observations in Hα and Mg II h&k lines Authors: Jejčič, Sonja; Heinzel, Petr; Schmieder, Brigitte; Gunár, Stanislav; Mein, Pierre; Mein, Nicole; Ruan, Guiping Bibcode: 2022ApJ...932....3J Altcode: We continued our investigation of the plasma characteristics of a quiescent prominence that occurred on 2017 March 30. The prominence was observed simultaneously by several instruments, including the Interface Region Imaging Spectrograph (IRIS) and the Multichannel Subtractive Double Pass (MSDP) spectrograph operating at the Meudon solar tower. We focused on IRIS Mg II h&k and MSDP Hα spectra, selecting 55 well-coaligned points within the prominence. We computed an extensive grid of 63,000 isothermal and isobaric 1D-slab prominence models with a non-LTE (i.e., departures from the local thermodynamic equilibrium) radiative transfer code. We then performed a 1.5D spectral inversion searching for an optimal model that best fits five parameters of the observed profiles (observables), namely, the integrated intensity of the Hα and Mg II k lines, the FWHM of both lines, and the ratio of intensities of the Mg II k and Mg II h lines. The latter is sensitive to temperature. Our results show that the prominence is a low-temperature structure, mostly below 10,000 K, with some excursions to higher values (up to 18,000 K) but also rather low temperatures (around 5000 K). The microturbulent velocity is typically low, peaking around 8 km s-1, and electron density values are of the order of 1010 cm-3. The peak effective thickness is 500 km, although the values range up to 5000 km. The studied prominence is rather optically thin in the Hα line and optically thick in the Mg II h&k lines. Title: Spectral inversion of H-alpha and MgII lines in quiescent prominences Authors: Heinzel, Petr; Schmieder, Brigitte; Ruan, Guiping; Mein, Pierre; Gunár, Stanislav; Jejcic, Sonja; Mein, Nicole Bibcode: 2021cosp...43E1764H Altcode: Recent spectral analysis of simultaneous H-alpha (MSDP) and MgII lines (IRIS) (Guiping et al. 2019) has revealed certain bifurcation in resulting models. Two solutions were found from the line inversions using the non-LTE modeling: relatively high kinetic temperature and low non-thermal motions or temperatures mostly compatible with standard ones plus non-thermal motions of the order of 16 km/sec. Here we will present an improved spectral line inversion technique which clearly prefers the latter solution. Strong non-thermal motions are then interpreted as a mixture of microturbulence and the line-of-sight dynamics of prominence fine-structure threads. A detailed multithread modeling with the 2D non-LTE code and stochastic distributions of threads (position, dynamics) is now in progress and we will show our preliminary results. Title: IRIS Mg II Observations and Non-LTE Modeling of Off-limb Spicules Authors: Tei, A.; Gunár, S.; Heinzel, P.; Okamoto, T. J.; Štěpán, J.; Jejčič, S.; Shibata, K. Bibcode: 2020AGUFMSH0010008T Altcode: We investigated the off-limb spicules observed in the Mg II h and k spectral lines by Interface Region Imaging Spectrograph (IRIS) in a solar polar coronal hole. We analyzed the large data set of obtained spectra to extract quantitative information about the line intensities, line shifts, and line widths. The observed Mg II line profiles are broad and double peaked at lower altitudes, broad but flat topped at middle altitudes, and narrow and single peaked with the largest Doppler shifts at higher altitudes. We used one-dimensional non-LTE vertical slab models (i.e., models that consider departures from local thermodynamic equilibrium) in single-slab and multi-slab configurations to interpret the observations and to investigate how a superposition of spicules along a line of sight (LOS) affects the synthetic Mg II line profiles. The employed multi-slab models are either static, i.e., without any LOS velocities, or assume randomly assigned LOS velocities of individual slabs, representing the spicule dynamics. We performed such single-slab and multi-slab modeling for a broad set of model input parameters and examined the dependence of the Mg II line profiles on these parameters. In this presentation, we demonstrate that the observed line widths of the Mg h and k line profiles are strongly affected by the presence of multiple spicules along the LOS. We also show that the profiles obtained at higher altitudes can be reproduced by single-slab models representing individual spicules. We found that the multi-slab model with a random distribution of the LOS velocities ranging from −25 to 25 km/s can well reproduce the width and the shape of the Mg II profiles observed at middle altitudes. Title: Metis: the Solar Orbiter visible light and ultraviolet coronal imager Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi, Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz; Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi, Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli, Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek; Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo, Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki, Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe; Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro; Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro; Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola; Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso, Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis, Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy, Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki, Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael; Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi, Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio; Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco; Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci, Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo; Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo; Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro; Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo, Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone, Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero, María; Amoruso, Mauro; Centonze, Vito Bibcode: 2020A&A...642A..10A Altcode: 2019arXiv191108462A
Aims: Metis is the first solar coronagraph designed for a space mission and is capable of performing simultaneous imaging of the off-limb solar corona in both visible and UV light. The observations obtained with Metis aboard the Solar Orbiter ESA-NASA observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona in a square field of view (FoV) of ±2.9° in width, with an inner circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7 R⊙ to about 9 R⊙, owing to the eccentricity of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter mission profile, Metis will be able to observe the solar corona from a close (0.28 AU, at the closest perihelion) vantage point, achieving increasing out-of-ecliptic views with the increase of the orbit inclination over time. Moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, allow longer-term studies of the off-limb coronal features, thus finally disentangling their intrinsic evolution from effects due to solar rotation.
Methods: Thanks to a novel occultation design and a combination of a UV interference coating of the mirrors and a spectral bandpass filter, Metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light channel also includes a broadband polarimeter able to observe the linearly polarised component of the K corona. The coronal images in both the UV H I Lyman-α and polarised visible light are obtained at high spatial resolution with a spatial scale down to about 2000 km and 15 000 km at perihelion, in the cases of the visible and UV light, respectively. A temporal resolution down to 1 s can be achieved when observing coronal fluctuations in visible light.
Results: The Metis measurements, obtained from different latitudes, will allow for complete characterisation of the main physical parameters and dynamics of the electron and neutral hydrogen/proton plasma components of the corona in the region where the solar wind undergoes the acceleration process and where the onset and initial propagation of coronal mass ejections (CMEs) take place. The near-Sun multi-wavelength coronal imaging performed with Metis, combined with the unique opportunities offered by the Solar Orbiter mission, can effectively address crucial issues of solar physics such as: the origin and heating/acceleration of the fast and slow solar wind streams; the origin, acceleration, and transport of the solar energetic particles; and the transient ejection of coronal mass and its evolution in the inner heliosphere, thus significantly improving our understanding of the region connecting the Sun to the heliosphere and of the processes generating and driving the solar wind and coronal mass ejections.
Conclusions: This paper presents the scientific objectives and requirements, the overall optical design of the Metis instrument, the thermo-mechanical design, and the processing and power unit; reports on the results of the campaigns dedicated to integration, alignment, and tests, and to the characterisation of the instrument performance; describes the operation concept, data handling, and software tools; and, finally, the diagnostic techniques to be applied to the data, as well as a brief description of the expected scientific products. The performance of the instrument measured during calibrations ensures that the scientific objectives of Metis can be pursued with success.

Metis website: http://metis.oato.inaf.it Title: On the Possibility of Detecting Helium D3 Line Polarization with Metis Authors: Heinzel, Petr; Štěpán, Jiři; Bemporad, Alessandro; Fineschi, Silvano; Jejčič, Sonja; Labrosse, Nicolas; Susino, Roberto Bibcode: 2020ApJ...900....8H Altcode: 2020arXiv200708940H Metis, the space coronagraph on board the Solar Orbiter, offers us new capabilities for studying eruptive prominences and coronal mass ejections (CMEs). Its two spectral channels, hydrogen Lα and visible light (VL), will provide for the first time coaligned and cotemporal images to study dynamics and plasma properties of CMEs. Moreover, with the VL channel (580-640 nm) we find an exciting possibility to detect the helium D3 line (587.73 nm) and its linear polarization. The aim of this study is to predict the diagnostic potential of this line regarding the CME thermal and magnetic structure. For a grid of models we first compute the intensity of the D3 line together with VL continuum intensity due to Thomson scattering on core electrons. We show that the Metis VL channel will detect a mixture of both, with predominance of the helium emission at intermediate temperatures between 30 and 50,000 K. Then we use the code HAZEL to compute the degree of linear polarization detectable in the VL channel. This is a mixture of D3 scattering polarization and continuum polarization. The former one is lowered in the presence of a magnetic field and the polarization axis is rotated (Hanle effect). Metis has the capability of measuring Q/I and U/I polarization degrees and we show their dependence on temperature and magnetic field. At T = 30,000 K we find a significant lowering of Q/I which is due to strongly enhanced D3 line emission, while depolarization at 10 G amounts roughly to 10%. Title: Signatures of Helium Continuum in Cool Flare Loops Observed by SDO/AIA Authors: Heinzel, Petr; Schwartz, Pavol; Lörinčík, Juraj; Koza, Július; Jejčič, Sonja; Kuridze, David Bibcode: 2020ApJ...896L..35H Altcode: 2020arXiv200600574H We present an analysis of off-limb cool flare loops observed by the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) during the gradual phase of SOL2017-09-10T16:06 X8.2-class flare. In the extreme-ultraviolet (EUV) channels starting from the 335 Å one, cool loops appear as dark structures against the bright loop arcade. These dark structures were precisely coaligned (spatially and temporally) with loops observed by Swedish Solar Telescope (SST) in emission lines of hydrogen and ionized calcium. A recently published semi-empirical model of cool loops based on SST observations serves to predict the level of hydrogen and helium recombination continua. The continua were synthesized using an approximate non-LTE (I.e., departures from local thermodynamic equilibrium) approach and theoretical spectra were then transformed to AIA signals. Comparison with signals detected inside the dark loops shows that only in AIA 211 Å channel the computed level of recombination continua is consistent with observations for some models, while in all other channels that are more distant from the continua edges the synthetic continuum is far too low. In analogy with on-disk observations of flares we interpret the surplus emission as due to numerous EUV lines emitted from hot but faint loops in front of the cool ones. Finally we briefly comment on failure of the standard absorption model when used for analysis of the dark-loop brightness. Title: IRIS Mg II Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole Authors: Tei, Akiko; Gunár, Stanislav; Heinzel, Petr; Okamoto, Takenori J.; Štěpán, Jiří; Jejčič, Sonja; Shibata, Kazunari Bibcode: 2020ApJ...888...42T Altcode: 2019arXiv191112243T We investigated the off-limb spicules observed in the Mg II h and k lines by IRIS in a solar polar coronal hole. We analyzed the large data set of obtained spectra to extract quantitative information about the line intensities, shifts, and widths. The observed Mg II line profiles are broad and double peaked at lower altitudes, broad but flat topped at middle altitudes, and narrow and single peaked with the largest Doppler shifts at higher altitudes. We use one-dimensional non-LTE vertical slab models (I.e., models that consider departures from local thermodynamic equilibrium) in single-slab and multi-slab configurations to interpret the observations and to investigate how a superposition of spicules along the line of sight (LOS) affects the synthetic Mg II line profiles. The used multi-slab models either are static, I.e., without any LOS velocities, or assume randomly assigned LOS velocities of individual slabs, representing the spicule dynamics. We conducted such single-slab and multi-slab modeling for a broad set of model input parameters and showed the dependence of the Mg II line profiles on these parameters. We demonstrated that the observed line widths of the h and k line profiles are strongly affected by the presence of multiple spicules along the LOS. We later showed that the profiles obtained at higher altitudes can be reproduced by single-slab models representing individual spicules. We found that the multi-slab model with a random distribution of the LOS velocities ranging from -25 to 25 km s-1 can well reproduce the width and the shape of Mg II profiles observed at middle altitudes. Title: Diagnostics of the Prominence Plasma from Hα and Mg II Spectral Observations Authors: Ruan, Guiping; Jejčič, Sonja; Schmieder, Brigitte; Mein, Pierre; Mein, Nicole; Heinzel, Petr; Gunár, Stanislav; Chen, Yao Bibcode: 2019ApJ...886..134R Altcode: The goal of this paper is to derive the physical conditions of the prominence observed on 2017 March 30. To do so, we use a unique set of data in Mg II lines obtained with the space-borne Interface Region Imaging Spectrograph (IRIS) and in Hα line with the ground-based Multi-Channel Subtractive Double Pass spectrograph operating at the Meudon solar tower. Here, we analyze the prominence spectra of Mg II h and k lines, and the Hα line in the part of the prominence which is visible in both sets of lines. We compute a grid of 1D NLTE (i.e., departures from the local thermodynamical equilibrium) models providing synthetic spectra of Mg II k and h, and Hα lines in a large space of model input parameters (temperature, density, pressure, and microturbulent velocity). We compare Mg II and Hα line profiles observed in 75 positions of the prominence with the synthetic profiles from the grid of models. These models allow us to compute the relationships between the integrated intensities and between the optical thickness in Hα and Mg II k lines. The optical thickness τ Hα is between 0.05 and 2, and {τ }Mg{{II}}{{k}}} is between 3 and 200. We show that the relationship of the observed integrated intensities agrees well with the synthetic integrated intensities for models with a higher microturbulence (16 km s-1) and T around 8000 K, ne = 1.5 × 1010 cm-3, p = 0.05 dyne. In this case, large microturbulence values could be a way to take into account the large mixed velocities existing in the observed prominence. Title: Spectral Diagnostics of Cool Flare Loops Observed by the SST. I. Inversion of the Ca II 8542 Å and Hβ Lines Authors: Koza, Július; Kuridze, David; Heinzel, Petr; Jejčič, Sonja; Morgan, Huw; Zapiór, Maciej Bibcode: 2019ApJ...885..154K Altcode: 2019arXiv190907356K Flare loops form an integral part of eruptive events, being detected in the range of temperatures from X-rays down to cool chromospheric-like plasmas. While hot loops are routinely observed by the Solar Dynamics Observatory’s Atmospheric Imaging Assembly, cool loops seen off-limb are rare. In this paper we employ unique observations of the SOL2017-09-10T16:06 X8.2-class flare which produced an extended arcade of loops. The Swedish 1 m Solar Telescope made a series of spectral images of the cool off-limb loops in the Ca II 8542 Å and the hydrogen Hβ lines. Our focus is on the loop apices. Non-local thermal equilibrium (non-LTE; i.e., departures from LTE) spectral inversion is achieved through the construction of extended grids of models covering a realistic range of plasma parameters. The Multilevel Accelerated Lambda Iterations code solves the non-LTE radiative-transfer problem in a 1D externally illuminated slab, approximating the studied loop segment. Inversion of the Ca II 8542 Å and Hβ lines yields two similar solutions, both indicating high electron densities around 2 × 1012 cm-3 and relatively large microturbulence around 25 km s-1. These are in reasonable agreement with other independent studies of the same or similar events. In particular, the high electron densities in the range 1012-1013 cm-3 are consistent with those derived from the Solar Dynamics Observatory’s Helioseismic and Magnetic Imager white-light observations. The presence of such high densities in solar eruptive flares supports the loop interpretation of the optical continuum emission of stars which manifest superflares. Title: Determination of the physical properties of an erupting prominence from SOHO/LASCO and UVCS observations Authors: Susino, R.; Bemporad, A.; Heinzel, P.; Jejčič, S.; Anzer, , U.; Dzifčáková, E. Bibcode: 2019NCimC..42...37S Altcode: We studied the physical conditions of an erupting prominence observed in the core of a coronal mass ejection, using combination of SOHO/LASCO-C2 visible-light images and SOHO/UVCS ultraviolet data. Measured intensities and profiles of the neutral-hydrogen Lyman- α and Lyman- β lines and the 977 Å C III line were used together with the visible-light brightness to derive the geometrical and physical parameters of the prominence, such as the line-of-sight apparent thickness, electron column density, kinetic temperature, and microturbolent velocity. These parameters were used to constrain a non-LTE ( i.e., out of local thermodynamic equilibrium) radiative-transfer model of the prominence that provides the effective thickness, electron density, and flow velocity, in a sample of points selected along the prominence. The prominence can be described as a hot structure with low electron density and very low gas pressure compared to typical quiescent prominences. Intensities of the hydrogen lines were also used for a detailed determination of the plasma line-of-sight filling factor, in the two prominence points where simultaneous and cospatial LASCO-C2 and UVCS observations were available. Title: High-density Off-limb Flare Loops Observed by SDO Authors: Jejčič, S.; Kleint, L.; Heinzel, P. Bibcode: 2018ApJ...867..134J Altcode: 2018arXiv181002431J The density distribution of flare loops and the mechanisms of their emission in the continuum are still open questions. On 2017 September 10, a prominent loop system appeared during the gradual phase of an X8.2 flare (SOL2017-09-10), visible in all passbands of SDO/AIA and in the white-light continuum of SDO/HMI. We investigate its electron density by taking into account all radiation processes in the flare loops, i.e., the Thomson continuum, hydrogen Paschen and Brackett recombination continua, as well as free-free continuum emission. We derive a quadratic function of the electron density for a given temperature and effective loop thickness. By absolutely calibrating SDO/HMI intensities, we convert the measured intensities into electron density at each pixel in the loops. For a grid of plausible temperatures between cool (6000 K) and hot (106 K) structures, the electron density is computed for representative effective thicknesses between 200 and 20,000 km. We obtain a relatively high maximum electron density, about 1013 cm-3. At such high electron densities, the Thomson continuum is negligible and therefore one would not expect a significant polarization degree in dense loops. We conclude that the Paschen and Brackett recombination continua are dominant in cool flare loops, while the free-free continuum emission is dominant for warmer and hot loops. Title: Statistical analysis of UV spectra of a quiescent prominence observed by IRIS Authors: Jejčič, S.; Schwartz, P.; Heinzel, P.; Zapiór, M.; Gunár, S. Bibcode: 2018A&A...618A..88J Altcode: 2018arXiv180705767J 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.

The movies associated to Figs. 1 and 7 are available at https://www.aanda.org Title: Hot prominence detected in the core of a coronal mass ejection. III. Plasma filling factor from UVCS Lyman-α and Lyman-β observations Authors: Susino, R.; Bemporad, A.; Jejčič, S.; Heinzel, P. Bibcode: 2018A&A...617A..21S Altcode: 2018arXiv180512465S Context. We study an erupting prominence embedded in the core of a coronal mass ejection that occurred on August 2, 2000, and focus on deriving the plasma filling factor of the prominence.
Aims: We explore two methods for measuring this factor along the line of sight. They are based on a combination of visible-light and ultraviolet spectroscopic observations.
Methods: Theoretical relationships for resonant scattering and collisional excitation were used to evaluate the intensity of the neutral hydrogen Lyman-α and Lyman-β lines in two prominence points where simultaneous and cospatial LASCO-C2 and UVCS data were available. Thermodynamic and geometrical parameters assumed for the calculation (i.e., electron column density, kinetic temperature, flow velocity, chromospheric Lyα and Lyβ intensities and profiles, and thickness of the prominence along the line of sight) are provided by both observations and the results of a detailed 1D non-local thermal equilibrium (non-LTE) radiative-transfer model of the prominence, developed in our previous work. The geometrical filling factor was derived from comparing the calculated and measured intensities of the two lines. The results were then checked against the non-LTE model in order to verify the reliability of the methods.
Results: The resulting filling factors are consistent with the model in both prominence points when the radiative and collisional components of the total intensity of the hydrogen lines are separated using the Lyα and Lyβ line intensities, which is required to estimate the filling factor. The exploration of the parameter space shows that the results are weakly sensitive to the plasma flow velocity, but depend more strongly on the assumed kinetic temperatures.
Conclusions: The combination of visible-light and ultraviolet Lyα and Lyβ data can be used to approximately estimate the line-of-sight geometrical filling factor in erupting prominences, but the proposed technique, which is model dependent, is reliable only for emission that is optically thin in the lines considered, a condition that is not in general representative of prominence plasma. Title: Plasma physical parameters of a prominence embedded in the core of a Coronal Mass Ejection Authors: Bemporad, Alessandro; Anzer, Ulrich; Heinzel, Petr; Jejcic, Sonja; Susino, Roberto Bibcode: 2018cosp...42E.267B Altcode: We determine the plasma physical parameters of an erupting prominence embedded in the core of a CME, combininging visible light coronagraphic images from SOHO/LASCO with UV spectra acquired by SOHO/UVCS. Strong UV emissions were detected in the hydrogen Lyman-α and Lyman-β lines and C III line. Visible light and UV intensities have been used to estimate the projected thickness and velocity of the prominence, together with the effective plasma temperature, microturbolent velocity, and column density. These parameters have been used to constrain 1D NLTE modeling of the erupting plasma, taking into account the effects of large flow velocities (Doppler dimming). Roughly one-half of considered points in the prominence body show a non-negligible Lyman-α optical thickness. Comparison between the calculated and the measured intensities of the two Lyman lines was also used to derive the geometrical filling factor. Results show that the erupting prominence plasma is relatively hot, with a low electron density, a wide range of effective thicknesses, a rather narrow range of radial flow velocities, and a microturbulence of about 25 km/s. This analysis provides a basis for future diagnostics of prominences using the METIS coronagraph on board the Solar Orbiter mission. Title: Hot Erupting Prominences in Cores of Cme's Authors: Heinzel, Petr; Bemporad, Alessandro; Anzer, Ulrich; Jejcic, Sonja; Susino, Roberto; Dzifcakova, Elena Bibcode: 2018cosp...42E1421H Altcode: Coronal mass ejections (CME) associated with prominence eruptions exhibit relatively coolmaterial in their cores. Such prominence plasmas were frequently detected in various spectrallines by SOHO/UVCS coronagraph and in the visible light by SOHO/LASCO as well as bySTEREO coronagraphs. UVCS provided excellent spectra of CME-core prominences and anextended catalogue of these data is available. We will present recent results of a hot prominence diagnostics using the hydrogen Lyman lines and the CIII line . The erupting prominence parameters are further constrained by the visible light observations from LASCO-C2. A novel non-LTE modeling based on such observations will be presented and we will highlight the diagnostic potential of the UV and visible light for future space coronagraphs like Metis on board the ESA Solar Orbiter mission. The plasma parameters of such hot prominences are compared with those obtained from numerical MHD simulations of erupting flux ropes surrounded by CMEs. Finally, we will also mention synergies with stellar analogues. Title: Visibility of Prominences Using the He I D3 Line Filter on the PROBA-3/ASPIICS Coronagraph Authors: Jejčič, S.; Heinzel, P.; Labrosse, N.; Zhukov, A. N.; Bemporad, A.; Fineschi, S.; Gunár, S. Bibcode: 2018SoPh..293...33J Altcode: 2018arXiv180700155J We determine the optimal width and shape of the narrow-band filter centered on the He I D3 line for prominence and coronal mass ejection (CME) observations with the ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) coronagraph onboard the PROBA-3 (Project for On-board Autonomy) satellite, to be launched in 2020. We analyze He I D3 line intensities for three representative non-local thermal equilibrium prominence models at temperatures 8, 30, and 100 kK computed with a radiative transfer code and the prominence visible-light (VL) emission due to Thomson scattering on the prominence electrons. We compute various useful relations at prominence line-of-sight velocities of 0, 100, and 300 km s−1 for 20 Å wide flat filter and three Gaussian filters with a full-width at half-maximum (FWHM) equal to 5, 10, and 20 Å to show the relative brightness contribution of the He I D3 line and the prominence VL to the visibility in a given narrow-band filter. We also discuss possible signal contamination by Na I D1 and D2 lines, which otherwise may be useful to detect comets. Our results mainly show that i) an optimal narrow-band filter should be flat or somewhere between flat and Gaussian with an FWHM of 20 Å in order to detect fast-moving prominence structures, ii) the maximum emission in the He I D3 line is at 30 kK and the minimal at 100 kK, and iii) the ratio of emission in the He I D3 line to the VL emission can provide a useful diagnostic for the temperature of prominence structures. This ratio is up to 10 for hot prominence structures, up to 100 for cool structures, and up to 1000 for warm structures. Title: Hot prominence detected in the core of a coronal mass ejection. II. Analysis of the C III line detected by SOHO/UVCS Authors: Jejčič, S.; Susino, R.; Heinzel, P.; Dzifčáková, E.; Bemporad, A.; Anzer, U. Bibcode: 2017A&A...607A..80J Altcode: Context. We study the physics of erupting prominences in the core of coronal mass ejections (CMEs) and present a continuation of a previous analysis.
Aims: We determine the kinetic temperature and microturbulent velocity of an erupting prominence embedded in the core of a CME that occurred on August 2, 2000 using the Ultraviolet Coronagraph and Spectrometer observations (UVCS) on board the Solar and Heliospheric Observatory (SOHO) simultaneously in the hydrogen Lα and C III lines. We develop the non-LTE (departures from the local thermodynamic equilibrium - LTE) spectral diagnostics based on Lα and Lβ measured integrated intensities to derive other physical quantities of the hot erupting prominence. Based on this, we synthesize the C III line intensity to compare it with observations.
Methods: Our method is based on non-LTE modeling of eruptive prominences. We used a general non-LTE radiative-transfer code only for optically thin prominence points because optically thick points do not allow the direct determination of the kinetic temperature and microturbulence from the line profiles. The input parameters of the code were the kinetic temperature and microturbulent velocity derived from the Lα and C III line widths, as well as the integrated intensity of the Lα and Lβ lines. The code runs in three loops to compute the radial flow velocity, electron density, and effective thickness as the best fit to the Lα and Lβ integrated intensities within the accuracy defined by the absolute radiometric calibration of UVCS data.
Results: We analyzed 39 observational points along the whole erupting prominence because for these points we found a solution for the kinetic temperature and microturbulent velocity. For these points we ran the non-LTE code to determine best-fit models. All models with τ0(Lα) ≤ 0.3 and τ0(C III) ≤ 0.3 were analyzed further, for which we computed the integrated intensity of the C III line using a two-level atom. The best agreement between computed and observed integrated intensity led to 30 optically thin points along the prominence. The results are presented as histograms of the kinetic temperature, microturbulent velocity, effective thickness, radial flow velocity, electron density, and gas pressure. We also show the relation between the microturbulence and kinetic temperature together with a scatter plot of computed versus observed C III integrated intensities and the ratio of the computed to observed C III integrated intensities versus kinetic temperature.
Conclusions: The erupting prominence embedded in the CME is relatively hot with a low electron density, a wide range of effective thicknesses, a rather narrow range of radial flow velocities, and a microturbulence of about 25 km s-1. This analysis shows a disagreement between observed and synthetic intensities of the C III line, the reason for which most probably is that photoionization is neglected in calculations of the ionization equilibrium. Alternatively, the disagreement might be due to non-equilibrium processes. Title: Hot prominence detected in the core of a coronal mass ejection: Analysis of SOHO/UVCS Lα and SOHO/LASCO visible-light observations Authors: Heinzel, P.; Susino, R.; Jejčič, S.; Bemporad, A.; Anzer, U. Bibcode: 2016A&A...589A.128H Altcode: Context. The paper deals with the physics of erupting prominences in the core of coronal mass ejections (CME).
Aims: We determine the physical parameters of an erupting prominence embedded in the core of a CME using SOHO/UVCS hydrogen Lα and Lβ lines and SOHO/LASCO visible light observations. In particular we analyze the CME event observed on August 2, 2000. We develop the non-LTE (NLTE; I.e. considering departures from the local thermodynamic equilibrium - LTE) spectral diagnostics based on Lα and visible light observations.
Methods: Our method is based on 1D NLTE modeling of eruptive prominences and takes into account the effect of large flow velocities, which reach up to 300 km s-1 for the studied event (the so-called Doppler dimming). The NLTE radiative-transfer method can be used for both optically thin and thick prominence structures. We combine spectroscopic UVCS observations of an erupting prominence in the core of a CME with visible light images from LASCO-C2 in order to derive the geometrical parameters like projected thickness and velocity, together with the effective temperature and column density of electrons. These are then used to constrain our NLTE radiative transfer modeling which provides the kinetic temperature, microturbulent velocity, gas pressure, ionization degree, the line opacities, and the prominence effective thickness (geometrical filling factor).
Results: Analysis was made for 69 observational points (spatial pixels) inside the whole erupting prominence. Roughly one-half of them show a non-negligible Lα optical thickness for flow velocity 300 km s-1 and about one-third for flow velocity 150 km s-1. All pixels with Lατ0 ≤ 0.3 have been considered for further analysis, which is presented in the form of statistical distributions (histograms) of various physical quantities such as the kinetic temperature, gas pressure, and electron density for two representative flow velocities (150 and 300 km s-1) and non-zero microturbulence. For two pixels co-temporal LASCO visible-light data are also available, which further constrains the diagnostics of the electron density and effective thickness. Detailed NLTE modeling is presented for various sets of input parameters.
Conclusions: The studied CME event shows that the erupting prominence expands to large volumes, meaning that it is a low-pressure structure with low electron densities and high temperatures. This analysis provides a basis for future diagnostics using the METIS coronagraph on board the Solar Orbiter mission. Title: Is it Possible to Use the Green Coronal Line Instead of X rays to Cancel an Effect of the Coronal Emissivity Deficit in Estimation of the Prominence Total Mass from Decrease of the EUV-corona Intensities? Authors: Schwartz, P.; Heinzel, P.; Jejčič, S.; Rybák, J.; Kotrč, P.; Fárník, F.; Kupryakov, Yu. A.; Deluca, E. E.; Golub, L.; Jibben, P. R.; Anzer, U.; Tlatov, A. G. .; Guseva, S. A. Bibcode: 2016ASPC..504...89S Altcode: Total masses of six quiescent prominences observed from April through June 2011 were estimated using multi-spectral observations (in EUV, X-rays, Hα, and Ca <small>II</small> H). The method for the total mass estimation is based on the fact that the intensity of the EUV solar corona at wavelengths below 912 Å is reduced at a prominence by the absorption in resonance continua (photoionisation) of hydrogen and possibly by helium and subsequently an amount of absorbed radiation is proportional to the column density of hydrogen and helium plasma. Moreover, the deficit of the coronal emissivity in volume occupied by the cool prominence plasma also contributes to the intensity decrease. The observations in X-rays which are not absorbed by the prominence plasma, allow us to separate these two mechanisms from each other. The X-ray observations of XRT onboard the Hinode satellite made with the Al-mesh focal filter were used because the X-ray coronal radiation formed in plasma of temperatures of the order of 106 K was registered and EUV spectral lines occurring in the 193, 211 and 335 Å channels of the Atmospheric Imaging Assembly of the Solar Dynamics Observatory satellite are also formed at such temperatures. Unfortunately, the Al-mesh filter has a secondary peak of the transmittance at around 171 Å which causes a contribution from the EUV corona to the measured data of up to 11 % in the quiet corona. Thus, absorption in prominence plasma influences XRT X-ray data when using the Al-mesh filter. On the other hand, other X-ray XRT filters are more sensitive to plasma of much higher temperatures (log T of the order of 7), thus observations using these filters cannot be used together with the AIA observations in the method for mass estimations. This problem could be solved using observations in the green coronal line instead of X-rays. Absorption of the green coronal line by a prominence plasma is negligible and this line is formed at temperatures of the order of 106 K. We compare values of the total mass of the prominence observed on 20 October 2012 on the SE limb estimated when using XRT X-ray observations and observations in the green coronal line obtained at Kislovodsk Mountain Astronomical Station of the Pulkovo observatory (Russia). Title: Prominence Visibility in Hinode/XRT Images Authors: Schwartz, P.; Jejčič, S.; Heinzel, P.; Anzer, U.; Jibben, P. R. Bibcode: 2015ApJ...807...97S Altcode: 2015arXiv150606078S In this paper we study the soft X-ray (SXR) signatures of one particular prominence. The X-ray observations used here were made by the Hinode/X-Ray Telescope instrument using two different filters. Both of them have a pronounced peak of the response function around 10 Å. One of them has a secondary smaller peak around 170 Å, which leads to a contamination of SXR images. The observed darkening in both of these filters has a very large vertical extension. The position and shape of the darkening correspond nicely with the prominence structure seen in SDO/AIA images. First, we have investigated the possibility that the darkening is caused by X-ray absorption. However, detailed calculations of the optical thickness in this spectral range show clearly that this effect is completely negligible. Therefore, the alternative is the presence of an extended region with a large emissivity deficit, which can be caused by the presence of cool prominence plasmas within an otherwise hot corona. To reproduce the observed darkening, one needs a very large extension along the line of sight of the region amounting to around 105 km. We interpret this region as the prominence spine, which is also consistent with SDO/AIA observations in EUV. Title: Multi-Wavelength Eclipse Observations of a Quiescent Prominence Authors: Jejčič, S.; Heinzel, P.; Zapiór, M.; Druckmüller, M.; Gunár, S.; Kotrč, P. Bibcode: 2014SoPh..289.2487J Altcode: 2014SoPh..tmp...30J We construct the maps of temperatures, geometrical thicknesses, electron densities and gas pressures in a quiescent prominence. For this we use the RGB signal of the prominence visible-light emission detected during the total solar eclipse of 1 August 2008 in Mongolia and quasi-simultaneous Hα spectra taken at Ondřejov Observatory. The method of disentangling the electron density and geometrical (effective) thickness was described by Jejčič and Heinzel (Solar Phys.254, 89 - 100, 2009) and is used here for the first time to analyse the spatial variations of prominence parameters. For the studied prominence we obtained the following range of parameters: temperature 6000 - 15 000 K, effective thickness 200 - 15000 km, electron density 5×109 - 1011 cm−3 and gas pressure 0.02 - 0.2 dyn cm−2 (assuming a fixed ionisation degree np/nH=0.5). The electron density increases towards the bottom of the prominence, which we explain by an enhanced photoionisation due to the incident solar radiation. To confirm this, we construct a two-dimensional radiative-transfer model with realistic prominence illumination. Title: A study of H I Lyman-alpha emission from prominences erupting in the intermediate corona and possible future applications for Solar Orbiter/METIS data Authors: Bemporad, Alessandro; Heinzel, Petr; Jejcic, Sonja; Susino, Roberto Bibcode: 2014cosp...40E.273B Altcode: Over almost the last 20 years hundreds of Coronal Mass Ejections (CME) have been observed by the UV Coronagraph Spectrometer (UVCS) onboard SOHO. For many of these events a significant emission in the HI Lyman-alpha lambda 1216 Å line was sampled during the transit across the slit of the erupting prominences embedded in the core of CMEs. The origin of this emission is completely different from what is typically observed by UVCS: because of the higher density and lower temperatures of such plasmas, the number of neutral H atoms is much larger than under typical coronal conditions, and the plasma is generally not optically thin at these wavelengths, as it is usually true for other coronal structures. Hence, the observed H I Lyman-alpha emission can be explained only if a radiative transport treatment across a moving plasma structure is considered. Once the proper boundary conditions are derived from the UV data, in combination with white light (WL) coronagraphic observations (from LASCO), we will show how the temperature and density of the erupting prominence could be derived even at large altitudes (typically larger than 0.6 solar radii above the limb), thus providing information on heating/cooling and ionization of the CME core during the eruption. These results are very important in the light of coronagraphic observations that will be provided by the METIS instrument onboard the Solar Orbiter: because METIS will contemporary observe the solar corona in WL and in UV (HI Lyman-alpha), it will be possible to derive, with a technique similar to what is shown here, very important information on prominence plasmas embedded in the core of CMEs and crossing the METIS instrument field of view. Title: Mapping prominence plasma parameters from eclipse observations Authors: Jejčič, Sonja; Heinzel, Petr; Zapiór, Maciej; Druckmüller, Miloslav; Gunár, Stanislav; Kotrč, Pavel Bibcode: 2014IAUS..300..420J Altcode: Using the eclipse observations, we construct the maps of quiescent prominence temperatures, electron densities, pressures and geometrical thicknesses. For this we use the RGB signal of prominence visible-light emission detected during the total solar eclipse on August 1, 2008 in Mongolia, and quasi-simultaneous Hα spectra taken at Ondřejov observatory. The method of disentangling the electron density and effective geometrical thickness was described by Jejčič & Heinzel (2009) and is used here for the first time to analyse the spatial variations of various prominence parameters. Title: Electron Densities in Quiescent Prominences Derived from Eclipse Observations Authors: Jejčič, S.; Heinzel, P. Bibcode: 2009SoPh..254...89J Altcode: We develop a diagnostic tool for determination of the electron densities in solar prominences using eclipse data. The method is based on analysis of the hydrogen Balmer-line intensities (namely Hα and Hβ) and the white-light emission due to Thomson scattering on the prominence electrons. Our approach represents a generalization of the ratio method already used by Koutchmy, Lebecq, and Stellmacher (Astron. Astrophys.119, 261, 1983). In this paper we use an extended grid of non-LTE prominence models of Gouttebroze, Heinzel, and Vial (Astron. Astrophys. Suppl. Ser.99, 513, 1993) and derive various useful relations between prominence radiation properties and electron densities. Simultaneously, an effective geometrical thickness of the prominence can also be obtained. As an example we apply our general technique to original eclipse data of Koutchmy, Lebecq, and Stellmacher (Astron. Astrophys.119, 261, 1983). Finally, we use our results to determine the color of prominences as it should be seen during total eclipses. Title: Eclipse Observations of Quiescent Prominences Authors: Jejcic, S.; Heinzel, P.; Kotrc, P.; Druckmuller, M. Bibcode: 2008ESPM...12.2.66J Altcode: In this study we demonstrate how to analyze the solar eclipse data taken by a digital camera. We use the observations of a quiescent prominence obtained during the total solar eclipse on March 29, 2006 (Side, Turkey). Using the RGB signal of the white light emission and co-temporal H? spectra taken at Ondrejov Observatory, we derive the electron density, temperature and geometrical thickness of the studied prominence. Title: White-Light Emission of Solar Prominences Authors: Jejčič, S.; Heinzel, P. Bibcode: 2007ASPC..368..325J Altcode: Using an extended grid of prominence models we compute the prominence white-light (WL) emission due to Thomson scattering and compare it with that in Hα. The ratio of the WL emission and the total emission can explain the color of prominences as observed during the total eclipses and can tell us whether the pink color of prominences is due to their intrinsic white-light emission or due to coronal contribution at the prominence location. We also show how this ratio depends on the prominence electron density, temperature and thickness. Title: Popolni Soncev mrk v Turciji, 29. marec 2006, Side, Turcija Title: Popolni Soncev mrk v Turciji, 29. marec 2006, Side, Turcija Title: Total Solar Eclipse in Turkey, March 29th, 2006, Side, Turkey. Authors: Jejcic, S.; Dintinjana, B.; Mikuz, H. Bibcode: 2006Spika..14..186J Altcode: No abstract at ADS Title: The Comparison of Spectroscopic Measurements of the Solar Rotation Authors: Jejčič, S.; Čadež, A. Bibcode: 2005HvaOB..29...11J Altcode: We studied the velocity field on the surface of the Sun measured by the Doppler shift of Fraunhofer Sodium lines Na-D_{2} at 5891.583 Å, Na-D_{1} at 5897.557 Å and Nickel line Ni I at 5894.505 Å. All the spectroscopic measurements were done at Ljubljana observatory on September 9, 10, 13 and 14 1999 using double monochromator DFS-12. The calibration was done through five telluric water lines in the vicinity of Sodium lines. With respect to telluric water lines Fraunhofer lines were analysed and through their Doppler velocity we determined the velocity field on the surface of the Sun. The data were fitted to the rotation model to determine the average solar angular (sidereal) coefficients, the average gravitational redshift velocity and the average parameters of the systematic limb shift for each line separately. Solar rotation coefficients determined by our measurements are compared with those of Howard and Harvey, Snodgrass and Ulrich, and Wittmann. Title: Final Results of the VT-2004 International Project /Koncni rezultati mednarodnega projekta VT-2004 Authors: Jejcic, S. Bibcode: 2005Spika..13...38J Altcode: No abstract at ADS Title: CCD Spectroscopy of Solar Rotation Authors: Jejčič, S.; Čadež, A. Bibcode: 2005ASSL..320..271J Altcode: 2005smp..conf..271J No abstract at ADS Title: Venus Transit 2004/Prehod Venere 2004 - Venera bo 8. junija 2004 preckala Soncevo ploskev Authors: Jejcic, S.; Cadez, A. Bibcode: 2004Spika..12..206J Altcode: No abstract at ADS Title: Velocity measurements by the double monochromator DFS-12 Authors: Jejčič, S.; Čadež, A. Bibcode: 2003HvaOB..27..197J Altcode: This study presents the observation of the velocity field on the surface of the Sun, measured by the Doppler shift of sodium D lines in the solar spectrum calibrated by the telluric water line. The observations were made on 9 September 1999 by the double monochromator DFS-12 at Ljubljana observatory. The data were used with a rotation model to determine the parameters of solar angular velocity, the gravitational redshift velocity as well as the parameters of the systematic limb shift. Title: Observations of velocity field on the surface of the sun Authors: Jejčič, S.; Čadež, A. Bibcode: 2002ESASP.506..959J Altcode: 2002ESPM...10..959J; 2002svco.conf..959J We studied the solar Doppler velocity field by scanning the frequency of sodium lines across the solar disk. We describe the double monochromator used for this task and discuss data reduction and calibration procedures. The data obtained during summer 1999 were used with a rotation model to determine two components of solar angular velocity, the gravitational redshift as well as an approximation to differential rotation.