On the Possibilities of Detecting Helium D3_3 Line Polarization with Metis

Space coronagraph Metis on board of the Solar Orbiter offers us new capabilities for studying eruptive prominences and coronal mass ejections (CME). Its two spectral channels, hydrogen L$\alpha$ and visible-light (VL) will provide, for the first time, co-aligned and co-temporal 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 D$_3$ line (587.73 nm) and its linear polarization. The aim of this study is to predict the diagnostics potential of this line regarding the CME thermal and magnetic structure. For a grid of models we first compute the intensity of the D$_3$ 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 - 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 D$_3$ 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 D$_3$ line emission, while depolarization at 10 G amounts roughly to 10 \%.Comment: 11 pages, 6 figures, accepted for publication in Ap

ALMA as a prominence thermometer: First observations

We present first prominence observations obtained with ALMA in Band 3 at the wavelength of 3 mm. High-resolution observations have been coaligned with the MSDP H$\alpha$ data from Wroclaw-Bialk\'{o}w large coronagraph at similar spatial resolution. We analyze one particular co-temporal snapshot, first calibrating both ALMA and MSDP data and then demonstrating a reasonable correlation between both. In particular we can see quite similar fine-structure patterns in both ALMA brightness temperature maps and MSDP maps of H$\alpha$ intensities. Using ALMA we intend to derive the prominence kinetic temperatures. However, having current observations only in one band, we use an independent diagnostic constraint which is the H$\alpha$ line integrated intensity. We develop an inversion code and show that it can provide realistic temperatures for brighter parts of the prominence where one gets a unique solution, while within faint structures such inversion is ill conditioned. In brighter parts ALMA serves as a prominence thermometer, provided that the optical thickness in Band 3 is large enough. In order to find a relation between brightness and kinetic temperatures for a given observed H$\alpha$ intensity, we constructed an extended grid of non-LTE prominence models covering a broad range of prominence parameters. We also show the effect of the plane-of-sky filling factor on our results.Comment: 9 pages, 3 figures, accepted for publication in the The Astrophysical Journal Letter

Geoarchaeology of the 1926 Seeberger Excavation - Jackson County, Iowa

In 1926, Paul Nesbitt discovered around 350 shards of clay pottery in Seeberger cave, located 6 miles north of Maquoketa, Iowa. It is unknown if these artifacts were made in Iowa, or brought over from neighboring states. For this project, Dr. Heinzel, Faith Luce and I traveled to the area to collect samples of clay and stone. We got close to the cave, but didn’t have the equipment to cross the river at the time. The area we collected our samples from is about 600 meters away from the original site. The samples will be used to characterize the site, along with GIS and drone imaging. We plan on going back to the site to do more work and collect more samples. We are currently analyzing the chemical and physical properties of the collected samples to determine if the local resources match the potter

On Broyden's method for the solution of the multilevel non-LTE radiation transfer problem

This study concerns the fast and accurate solution of multilevel non-LTE radiation transfer problems. We propose and evaluate an alternative iterative scheme to the classical MALI method. Our study is indeed based on the application of Broyden's method for the solution of nonlinear systems of equations. Comparative tests, in 1D plane-parallel geometry, between the popular MALI method and our alternative method are discussed. The Broyden method is typically 4.5 times faster than MALI. It makes it also fairly competitive with Gauss-Seidel and Successive Over-Relaxation methods developed after MALI.Comment: Accepted for publication in A&

Prominence observations with ALMA

This review comes at the time when ALMA successfully obtained the first regular observations of both a prominence and a filament. These observations have a spatial resolution of 1-2 arcsec, far better than previous prominence observations in the mm/sub-mm radio domain. The achieved resolution is compatible with the cotemporal ground-based coronagraphic observations in the hydrogen Hα line that accompany the ALMA Band 3 prominence observations. A core part of this review is the description and analysis of these pioneering ALMA observations of a quiescent prominence, focusing on various physical and geometrical properties of the observed prominence fine structures. We also summarize the basic physical processes behind the formation of mm/sub-mm continua under prominence conditions and describe the plasma diagnostics potential of ALMA solar observations. Finally, we discuss future prospects of ALMA prominence observations and the value of coordinated optical and UV spectra and images

On the physical nature of the so-called prominence tornadoes

Funding: Open access publishing supported by the National Technical Library in Prague. S. Gunár and P. Heinzel acknowledge the support from grant 22-34841S of the Czech Science Foundation (GAČR). S. Gunár, P. Heinzel, and M. Zapiór acknowledge the support from the project RVO:67985815 of the Astronomical Institute of the Czech Academy of Sciences. N. Labrosse acknowledges support from STFC grant ST/T000422/1. M. Luna acknowledges support through the Ramón y Cajal fellowship RYC2018-026129-I from the Spanish Ministry of Science and Innovation, the Spanish National Research Agency (Agencia Estatal de Investigación), the European Social Fund through Operational Program FSE 2014 of Employment, Education and Training and the Universitat de les Illes Balears. This publication is part of the R + D + i project PID2020-112791GB-I00, financed by MCIN/AEI/10.13039/501100011033. T. Kucera acknowledges support of the NASA Heliophysics ISFM program. D.H.M. would like to thank the STFC for support via consolidated grant ST/W001195/1.The term ‘tornado’ has been used in recent years to describe several solar phenomena, from large-scale eruptive prominences to small-scale photospheric vortices. It has also been applied to the generally stable quiescent prominences, sparking a renewed interest in what historically was called ‘prominence tornadoes’. This paper carries out an in-depth review of the physical nature of ‘prominence tornadoes’, where their name subconsciously makes us think of violent rotational dynamics. However, after careful consideration and analysis of the published observational data and theoretical models, we conclude that ‘prominence tornadoes’ do not differ in any substantial way from other stable solar prominences. There is simply no unequivocal observational evidence of sustained and coherent rotational movements in quiescent prominences that would justify a distinct category of prominences sharing the name with the well-known atmospheric phenomenon. The visual impression of the column-like silhouettes, the perceived helical motions, or the suggestive Doppler-shift patterns all have a simpler, more likely explanation. They are a consequence of projection effects combined with the presence of oscillations and/or counter-streaming flows. ‘Prominence tornadoes’ are thus just manifestations of the complex nature of solar prominences when observed in specific projections. These coincidental viewing angles, together with the presence of fine-structure dynamics and simple yet profoundly distorting projection effects, may sometimes play havoc with our intuitive understanding of perceived shapes and motions, leading to the incorrect analogy with atmospheric tornadoes.Publisher PDFPeer reviewe

Quantitative multilevel analysis of central metabolism in developing oilseeds of oilseed rape during in vitro culture

Seeds provide the basis for many food, feed, and fuel products. Continued increases in seed yield, composition, and quality require an improved understanding of how the developing seed converts carbon and nitrogen supplies into storage. Current knowledge of this process is often based on the premise that transcriptional regulation directly translates via enzyme concentration into flux. In an attempt to highlight metabolic control, we explore genotypic differences in carbon partitioning for in vitro cultured developing embryos of oilseed rape (Brassica napus). We determined biomass composition as well as 79 net fluxes, the levels of 77 metabolites, and 26 enzyme activities with specific focus on central metabolism in nine selected germplasm accessions. Overall, we observed a tradeoff between the biomass component fractions of lipid and starch. With increasing lipid content over the spectrum of genotypes, plastidic fatty acid synthesis and glycolytic flux increased concomitantly, while glycolytic intermediates decreased. The lipid/starch tradeoff was not reflected at the proteome level, pointing to the significance of (posttranslational) metabolic control. Enzyme activity/flux and metabolite/flux correlations suggest that plastidic pyruvate kinase exerts flux control and that the lipid/starch tradeoff is most likely mediated by allosteric feedback regulation of phosphofructokinase and ADP-glucose pyrophosphorylase. Quantitative data were also used to calculate in vivo mass action ratios, reaction equilibria, and metabolite turnover times. Compounds like cyclic 39,59-AMP and sucrose-6-phosphate were identified to potentially be involved in so far unknown mechanisms of metabolic control. This study provides a rich source of quantitative data for those studying central metabolism

Seed architecture shapes embryo metabolism in oilseed rape

Constrained to develop within the seed, the plant embryo must adapt its shape and size to fit the space available. Here, we demonstrate how this adjustment shapes metabolism of photosynthetic embryo. Noninvasive NMR-based imaging of the developing oilseed rape (Brassica napus) seed illustrates that, following embryo bending, gradients in lipid concentration became established. These were correlated with the local photosynthetic electron transport rate and the accumulation of storage products. Experimentally induced changes in embryo morphology and/or light supply altered these gradients and were accompanied by alterations in both proteome and metabolome. Tissue-specific metabolic models predicted that the outer cotyledon and hypocotyl/radicle generate the bulk of plastidic reductant/ATP via photosynthesis, while the inner cotyledon, being enclosed by the outer cotyledon, is forced to grow essentially heterotrophically. Under field-relevant highlight conditions, major contribution of the ribulose-1,5-bisphosphate carboxylase/oxygenase-bypass to seed storage metabolism is predicted for the outer cotyledon and the hypocotyl/radicle only. Differences between in vitro- versus in planta-grown embryos suggest that metabolic heterogeneity of embryo is not observable by in vitro approaches. We conclude that in vivo metabolic fluxes are locally regulated and connected to seed architecture, driving the embryo toward an efficient use of available light and space

The Influence of the Solar Coronal Radiation on Coronal Plasma Structures, I: Determination of the Incident Coronal Radiation

Coronal structures receive radiation not only from the solar disc, but also from the corona. This height-dependent incident radiation plays a crucial role in the excitation and the ionisation of the illuminated plasma. The aim of this article is to present a method for computing the detailed incident radiation coming from the solar corona, which is perceived at a point located at an arbitrary height. The coronal radiation is calculated by integrating the radiation received at a point in the corona over all of the corona visible from this point. The emission from the corona at all wavelengths of interest is computed using atomic data provided by CHIANTI. We obtain the spectrum illuminating points located at varying heights in the corona at wavelengths between 100 and 912 Å when photons can ionise H or He atoms and ions in their ground states. As expected, individual spectral lines will contribute most at the height within the corona where the local temperature is closest to their formation temperature. As there are many spectral lines produced by many ions, the coronal intensity cannot be assumed to vary in the same way at all wavelengths and so must be calculated for each separate height that is to be considered. This code can be used to compute the spectrum from the corona illuminating a point at any given height above the solar surface. This brings a necessary improvement to models where an accurate determination of the excitation and ionisation states of coronal plasma structures is crucial