Sparse inversion of Stokes profiles. I. Two-dimensional Milne-Eddington inversions

Inversion codes are numerical tools used for the inference of physical properties from the observations. Despite their success, the quality of current spectropolarimetric observations and those expected in the near future presents a challenge to current inversion codes. The pixel-by-pixel strategy of inverting spectropolarimetric data that we currently utilize needs to be surpassed and improved. The inverted physical parameters have to take into account the spatial correlation that is present in the data and that contains valuable physical information. We utilize the concept of sparsity or compressibility to develop an new generation of inversion codes for the Stokes parameters. The inversion code uses numerical optimization techniques based on the idea of proximal algorithms to impose sparsity. In so doing, we allow for the first time to exploit the presence of spatial correlation on the maps of physical parameters. Sparsity also regularizes the solution by reducing the number of unknowns. We compare the results of the new inversion code with pixel-by-pixel inversions, demonstrating the increase in robustness of the solution. We also show how the method can easily compensate for the effect of the telescope point spread function, producing solutions with an enhanced contrast.Comment: 13 pages, 8 figures, accepted for publication in A&

Real-time multiframe blind deconvolution of solar images

The quality of images of the Sun obtained from the ground are severely limited by the perturbing effect of the turbulent Earth's atmosphere. The post-facto correction of the images to compensate for the presence of the atmosphere require the combination of high-order adaptive optics techniques, fast measurements to freeze the turbulent atmosphere and very time consuming blind deconvolution algorithms. Under mild seeing conditions, blind deconvolution algorithms can produce images of astonishing quality. They can be very competitive with those obtained from space, with the huge advantage of the flexibility of the instrumentation thanks to the direct access to the telescope. In this contribution we leverage deep learning techniques to significantly accelerate the blind deconvolution process and produce corrected images at a peak rate of ~100 images per second. We present two different architectures that produce excellent image corrections with noise suppression while maintaining the photometric properties of the images. As a consequence, polarimetric signals can be obtained with standard polarimetric modulation without any significant artifact. With the expected improvements in computer hardware and algorithms, we anticipate that on-site real-time correction of solar images will be possible in the near future.Comment: 16 pages, 12 figures, accepted for publication in A&

Observations of Ellerman bomb emission features in He I D3 and He I 10830 {\AA}

Context. Ellerman bombs (EBs) are short-lived emission features, characterized by extended wing emission in hydrogen Balmer lines. Until now, no distinct signature of EBs has been found in the He I 10830 {\AA} line, and conclusive observations of EBs in He I D 3 have never been reported. Aims. We aim to study the signature of EBs in neutral helium triplet lines. Methods. The observations consist of 10 consecutive SST/TRIPPEL raster scans close to the limb, featuring the H$\beta$, He I D3 and He I 10830 {\AA} spectral regions. We also obtained raster scans with IRIS and make use of the SDO/AIA 1700 {\AA} channel. We use Hazel to invert the neutral helium triplet lines. Results. Three EBs in our data show distinct emission signatures in neutral helium triplet lines, most prominently visible in the He I D3 line. The helium lines have two components: a broad and blue-shifted emission component associated with the EB, and a narrower absorption component formed in the overlying chromosphere. One of the EBs in our data shows evidence of strong velocity gradients in its emission component. The emission component of the other two EBs could be fitted using a constant slab. Our analysis hints towards thermal Doppler motions having a large contribution to the broadening for helium and IRIS lines. We conclude that the EBs must have high temperatures to exhibit emission signals in neutral helium triplet lines. An order of magnitude estimate places our observed EBs in the range of $T\sim 2\cdot 10^4-10^5$ K.Comment: 15 pages, 14 figure

The arogenate dehydratase ADT2 is essential for seed development in Arabidopsis

Phenylalanine (Phe) biosynthesis in plants is a key process, as Phe serves as precursor of proteins and phenylpropanoids. The prephenate pathway connects chorismate, final product of the shikimate pathway, with the biosynthesis of Phe and Tyr. Two alternative routes of Phe biosynthesis have been reported: one depending of arogenate, and the other of phenylpyruvate. Whereas the arogenate pathway is considered the main route, the role of the phenylpyruvate pathway remains unclear. Here, we report that the deficiency in ADT2, a bifunctional arogenate dehydratase (ADT)/ prephenate dehydratase (PDT) enzyme, causes embryo arrest and seed abortion. This result makes a clear distinction between the essential role of ADT2 and the five remaining ADTs from Arabidopsis, which display mostly overlapping functions. We have found that PHA2, a monofunctional PDT from yeast, restores the adt2 phenotype when is targeted within the plastids, but not when is expressed in the cytosol. Similar results can be obtained by expressing ADT3, a monofunctional ADT. These results suggest that Phe can be synthesized from phenylpyruvate or arogenate when the bifunctional ADT2 is replaced by other ADT or PDT enzymes during seed formation, highlighting the importance of Phe for embryo development, and providing further insights into the plasticity of Phe biosynthesis.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Biochemical regulation of arginine biosynthesis in plants

Arginine plays a relevant role in plant metabolism due to its importance as building block of proteins but also as precursor of multiple secondary metabolites, polyamines and nitric oxide. Importantly, arginine frequently plays an essential role as a major nitrogen storage form in seeds and other vegetative tissues and its mobilization provides an efficient flux of nitrogen for different physiological processes [1][2][3]. Despite its importance, the biochemical regulation and kinetics of the enzymes involved in arginine biosynthesis remains poorly characterized in plants. In this work, we provide new knowledge about the biochemical regulation of the three enzymes involved in the last steps of the arginine pathway: ornithine transcarbamoylase (OTC), argininosuccinate synthetase (ASSY), and argininosuccinate lyase (ASL). Our results indicate that these enzymes are regulated by the concentration of different amino acids and metabolites, including arginine, suggesting that feedback regulatory loops could play and important role in the homeostasis of this amino acid. Besides, these regulatory mechanisms seem to have been subjected to a progressive refinement during the evolution of land plants, pointing towards a coevolution with the higher requirements of arginine in seed plants.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Morfología polínica del género Allagopappus Cass. (Asteraceae: Inuleae), endémico de las Islas Canarias, España

XV lnternational A.P.L.E. Symposium of Palynolog

Morfología polínica y su implicación en la taxonomía de las especies endémicas del complejo Gonospermum Less., Lugoa D.C. y Tanacetum L. (Asteraceae: Anthemideae) en las Islas Canarias, España

XV lnternational A.P.L.E. Symposium of Palynolog

On the magnetism and dynamics of prominence legs hosting tornadoes

Solar tornadoes are dark vertical filamentary structures observed in the extreme ultraviolet associated with prominence legs and filament barbs. Their true nature and relationship to prominences requires understanding their magnetic structure and dynamic properties. Recently, a controversy has arisen: is the magnetic field organized forming vertical, helical structures or is it dominantly horizontal? And concerning their dynamics, are tornadoes really rotating or is it just a visual illusion? Here, we analyze four consecutive spectropolarimetric scans of a prominence hosting tornadoes on its legs which help us shed some light on their magnetic and dynamical properties. We show that the magnetic field is very smooth in all the prominence, probably an intrinsic property of the coronal field. The prominence legs have vertical helical fields that show slow temporal variation probably related to the motion of the fibrils. Concerning the dynamics, we argue that 1) if rotation exists, it is intermittent, lasting no more than one hour, and 2) the observed velocity pattern is also consistent with an oscillatory velocity pattern (waves).Comment: accepted for publication in Ap

Espectro polínico de algunas mieles producidas en Tenerife y La Gomera (Islas Canarias, España)

XV lnternational A.P.L.E. Symposium of Palynolog