TY  - JOUR
A1  - Martinez Gonzalez, M. J.
A1  - Pastor Yabar, A.
A1  - Lagg, A.
A1  - Asensio Ramos, A.
A1  - Collados Vera, M.
A1  - Solanki, S. K.
A1  - Balthasar, H.
A1  - Berkefeld, T.
A1  - Denker, Carsten
A1  - Doerr, H. P.
A1  - Feller, A.
A1  - Franz, M.
A1  - González Manrique, Sergio Javier
A1  - Hofmann, A.
A1  - Kneer, F.
A1  - Kuckein, Christoph
A1  - Louis, R.
A1  - von der Lühe, O.
A1  - Nicklas, H.
A1  - Orozco, D.
A1  - Rezaei, R.
A1  - Schlichenmaier, R.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Verma, Meetu
A1  - Waldman, T.
A1  - Volkmer, R.
T1  - Inference of magnetic fields in the very quiet Sun
JF  - Journal of geophysical research : Earth surface
N2  - Context. Over the past 20 yr, the quietest areas of the solar surface have revealed a weak but extremely dynamic magnetism occurring at small scales (<500 km), which may provide an important contribution to the dynamics and energetics of the outer layers of the atmosphere. Understanding this magnetism requires the inference of physical quantities from high-sensitivity spectro-polarimetric data with high spatio-temporal resolution. Aims. We present high-precision spectro-polarimetric data with high spatial resolution (0.4") of the very quiet Sun at 1.56 mu m obtained with the GREGOR telescope to shed some light on this complex magnetism. Methods. We used inversion techniques in two main approaches. First, we assumed that the observed profiles can be reproduced with a constant magnetic field atmosphere embedded in a field-free medium. Second, we assumed that the resolution element has a substructure with either two constant magnetic atmospheres or a single magnetic atmosphere with gradients of the physical quantities along the optical depth, both coexisting with a global stray-light component. Results. Half of our observed quiet-Sun region is better explained by magnetic substructure within the resolution element. However, we cannot distinguish whether this substructure comes from gradients of the physical parameters along the line of sight or from horizontal gradients (across the surface). In these pixels, a model with two magnetic components is preferred, and we find two distinct magnetic field populations. The population with the larger filling factor has very weak (similar to 150 G) horizontal fields similar to those obtained in previous works. We demonstrate that the field vector of this population is not constrained by the observations, given the spatial resolution and polarimetric accuracy of our data. The topology of the other component with the smaller filling factor is constrained by the observations for field strengths above 250 G: we infer hG fields with inclinations and azimuth values compatible with an isotropic distribution. The filling factors are typically below 30%. We also find that the flux of the two polarities is not balanced. From the other half of the observed quiet-Sun area similar to 50% are two-lobed Stokes V profiles, meaning that 23% of the field of view can be adequately explained with a single constant magnetic field embedded in a non-magnetic atmosphere. The magnetic field vector and filling factor are reliable inferred in only 50% based on the regular profiles. Therefore, 12% of the field of view harbour hG fields with filling factors typically below 30%. At our present spatial resolution, 70% of the pixels apparently are non-magnetised.
KW  - Sun: atmosphere
KW  - Sun: magnetic fields
KW  - techniques: polarimetric
KW  - methods: observational
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201628449
SN  - 1432-0746
VL  - 596
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Verma, Meetu
A1  - Denker, Carsten
A1  - Balthasar, H.
A1  - Kuckein, Christoph
A1  - González Manrique, Sergio Javier
A1  - Sobotka, M.
A1  - Gonzalez, N. Bello
A1  - Hoch, S.
A1  - Diercke, Andrea
A1  - Kummerow, Philipp
A1  - Berkefeld, T.
A1  - Collados Vera, M.
A1  - Feller, A.
A1  - Hofmann, A.
A1  - Kneer, F.
A1  - Lagg, A.
A1  - Löhner-Böttcher, J.
A1  - Nicklas, H.
A1  - Pastor Yabar, A.
A1  - Schlichenmaier, R.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Schubert, M.
A1  - Sigwarth, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Horizontal flow fields in and around a small active region The transition period between flux emergence and decay
JF  - Polymers
N2  - Context. The solar magnetic field is responsible for all aspects of solar activity. Thus, emergence of magnetic flux at the surface is the first manifestation of the ensuing solar activity. Aims. Combining high-resolution and synoptic observations aims to provide a comprehensive description of flux emergence at photospheric level and of the growth process that eventually leads to a mature active region. Methods. The small active region NOAA 12118 emerged on 2014 July 17 and was observed one day later with the 1.5-m GREGOR solar telescope on 2014 July 18. High-resolution time-series of blue continuum and G-band images acquired in the blue imaging channel (BIC) of the GREGOR Fabry-Perot Interferometer (GFPI) were complemented by synoptic line-of-sight magnetograms and continuum images obtained with the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). Horizontal proper motions and horizontal plasma velocities were computed with local correlation tracking (LCT) and the differential affine velocity estimator (DAVE), respectively. Morphological image processing was employed to measure the photometric and magnetic area, magnetic flux, and the separation profile of the emerging flux region during its evolution. Results. The computed growth rates for photometric area, magnetic area, and magnetic flux are about twice as high as the respective decay rates. The space-time diagram using HMI magnetograms of five days provides a comprehensive view of growth and decay. It traces a leaf-like structure, which is determined by the initial separation of the two polarities, a rapid expansion phase, a time when the spread stalls, and a period when the region slowly shrinks again. The separation rate of 0.26 km s(-1) is highest in the initial stage, and it decreases when the separation comes to a halt. Horizontal plasma velocities computed at four evolutionary stages indicate a changing pattern of inflows. In LCT maps we find persistent flow patterns such as outward motions in the outer part of the two major pores, a diverging feature near the trailing pore marking the site of upwelling plasma and flux emergence, and low velocities in the interior of dark pores. We detected many elongated rapidly expanding granules between the two major polarities, with dimensions twice as large as the normal granules.
KW  - Sun: photosphere
KW  - Sun: magnetic fields
KW  - techniques: image processing
KW  - methods: data analysis
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201628380
SN  - 1432-0746
VL  - 596
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Gonzalez Manrique, Sergio Javier
A1  - Kuckein, Christoph
A1  - Pastor Yabar, A.
A1  - Collados Vera, M.
A1  - Denker, Carsten
A1  - Fischer, C. E.
A1  - Gömöry, P.
A1  - Diercke, Andrea
A1  - Gonzalez, N. Bello
A1  - Schlichenmaier, R.
A1  - Balthasar, H.
A1  - Berkefeld, T.
A1  - Feller, A.
A1  - Hoch, S.
A1  - Hofmann, A.
A1  - Kneer, F.
A1  - Lagg, A.
A1  - Nicklas, H.
A1  - Orozco Suarez, D.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Verma, Meetu
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Fitting peculiar spectral profiles in He I 10830 angstrom absorption features
JF  - Astronomische Nachrichten = Astronomical notes
N2  - The new generation of solar instruments provides better spectral, spatial, and temporal resolution for a better understanding of the physical processes that take place on the Sun. Multiple-component profiles are more commonly observed with these instruments. Particularly, the He i 10830 triplet presents such peculiar spectral profiles, which give information on the velocity and magnetic fine structure of the upper chromosphere. The purpose of this investigation is to describe a technique to efficiently fit the two blended components of the He i 10830 triplet, which are commonly observed when two atmospheric components are located within the same resolution element. The observations used in this study were taken on 2015 April 17 with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-m GREGOR solar telescope, located at the Observatorio del Teide, Tenerife, Spain. We apply a double-Lorentzian fitting technique using Levenberg-Marquardt least-squares minimization. This technique is very simple and much faster than inversion codes. Line-of-sight Doppler velocities can be inferred for a whole map of pixels within just a few minutes. Our results show sub-and supersonic downflow velocities of up to 32 km s(-1) for the fast component in the vicinity of footpoints of filamentary structures. The slow component presents velocities close to rest. (C) 2016 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim
KW  - Sun: chromosphere
KW  - methods: data analysis
KW  - techniques: spectroscopic
KW  - line: profiles
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201512433
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1057
EP  - 1063
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Verma, Meetu
A1  - Denker, Carsten
A1  - Böhm, F.
A1  - Balthasar, H.
A1  - Fischer, C. E.
A1  - Kuckein, Christoph
A1  - Gonzalez, N. Bello
A1  - Berkefeld, T.
A1  - Collados Vera, M.
A1  - Diercke, Andrea
A1  - Feller, A.
A1  - Gonzalez Manrique, Sergio Javier
A1  - Hofmann, A.
A1  - Lagg, A.
A1  - Nicklas, H.
A1  - Orozco Suarez, D.
A1  - Pator Yabar, A.
A1  - Rezaei, R.
A1  - Schlichenmaier, R.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396
JF  - Astronomische Nachrichten = Astronomical notes
N2  - Improved measurements of the photospheric and chromospheric three-dimensional magnetic and flow fields are crucial for a precise determination of the origin and evolution of active regions. We present an illustrative sample of multi-instrument data acquired during a two-week coordinated observing campaign in August 2015 involving, among others, the GREGOR solar telescope (imaging and near-infrared spectroscopy) and the space missions Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS). The observations focused on the trailing part of active region NOAA 12396 with complex polarity inversion lines and strong intrusions of opposite polarity flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV spectral profiles in the photospheric Si i.1082.7 nm line, the chromospheric He I lambda 1083.0 nm triplet, and the photospheric Ca I lambda 1083.9 nm line. Carefully calibrated GRIS scans of the active region provided maps of Doppler velocity and magnetic field at different atmospheric heights. We compare quick-look maps with those obtained with the " Stokes Inversions based on Response functions" (SIR) code, which furnishes deeper insight into the magnetic properties of the region. We find supporting evidence that newly emerging flux and intruding opposite polarity flux are hampering the formation of penumbrae, i.e., a penumbra fully surrounding a sunspot is only expected after cessation of flux emergence in proximity to the sunspots. (C) 2016 WILEY-VCH Verlag GmbH& Co.KGaA, Weinheim
KW  - Sun: magnetic fields
KW  - sunspots
KW  - methods: data analysis
KW  - techniques: polarimetric
KW  - techniques: spectroscopic
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612447
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1090
EP  - 1098
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Denker, Carsten
A1  - Kuckein, Christoph
A1  - Verma, Meetu
A1  - Manrique Gonzalez, Sergio Javier Gonzalez
A1  - Diercke, Andrea
A1  - Enke, Harry
A1  - Klar, Jochen
A1  - Balthasar, Horst
A1  - Louis, Rohan E.
A1  - Dineva, Ekaterina Ivanova
T1  - High-cadence Imaging and Imaging Spectroscopy at the GREGOR Solar Telescope-A Collaborative Research Environment for High-resolution Solar Physics
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series
N2  - In high-resolution solar physics, the volume and complexity of photometric, spectroscopic, and polarimetric ground-based data significantly increased in the last decade, reaching data acquisition rates of terabytes per hour. This is driven by the desire to capture fast processes on the Sun and the necessity for short exposure times "freezing" the atmospheric seeing, thus enabling ex post facto image restoration. Consequently, large-format and high-cadence detectors are nowadays used in solar observations to facilitate image restoration. Based on our experience during the "early science" phase with the 1.5 m GREGOR solar telescope (2014–2015) and the subsequent transition to routine observations in 2016, we describe data collection and data management tailored toward image restoration and imaging spectroscopy. We outline our approaches regarding data processing, analysis, and archiving for two of GREGOR's post-focus instruments (see http://gregor.aip.de), i.e., the GREGOR Fabry–Pérot Interferometer (GFPI) and the newly installed High-Resolution Fast Imager (HiFI). The heterogeneous and complex nature of multidimensional data arising from high-resolution solar observations provides an intriguing but also a challenging example for "big data" in astronomy. The big data challenge has two aspects: (1) establishing a workflow for publishing the data for the whole community and beyond and (2) creating a collaborative research environment (CRE), where computationally intense data and postprocessing tools are colocated and collaborative work is enabled for scientists of multiple institutes. This requires either collaboration with a data center or frameworks and databases capable of dealing with huge data sets based on virtual observatory (VO) and other community standards and procedures.
KW  - astronomical databases
KW  - methods: data analysis
KW  - Sun: chromosphere
KW  - Sun: photosphere
KW  - techniques: image processing
KW  - techniques: spectroscopic
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4365/aab773
SN  - 0067-0049
SN  - 1538-4365
VL  - 236
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Denker, Carsten
A1  - Dineva, Ekaterina Ivanova
A1  - Balthasar, Horst
A1  - Verma, Meetu
A1  - Kuckein, Christoph
A1  - Diercke, Andrea
A1  - Manrique Gonzalez, Sergio Javier Gonzalez
T1  - Image Quality in High-resolution and High-cadence Solar Imaging
JF  - Solar physics : a journal for solar and solar-stellar research and the study of solar terrestrial physics
N2  - Broad-band imaging and even imaging with a moderate bandpass (about 1 nm) provides a photon-rich environment, where frame selection (lucky imaging) becomes a helpful tool in image restoration, allowing us to perform a cost-benefit analysis on how to design observing sequences for imaging with high spatial resolution in combination with real-time correction provided by an adaptive optics (AO) system. This study presents high-cadence (160 Hz) G-band and blue continuum image sequences obtained with the High-resolution Fast Imager (HiFI) at the 1.5-meter GREGOR solar telescope, where the speckle-masking technique is used to restore images with nearly diffraction-limited resolution. The HiFI employs two synchronized large-format and high-cadence sCMOS detectors. The median filter gradient similarity (MFGS) image-quality metric is applied, among others, to AO-corrected image sequences of a pore and a small sunspot observed on 2017 June 4 and 5. A small region of interest, which was selected for fast-imaging performance, covered these contrastrich features and their neighborhood, which were part of Active Region NOAA 12661. Modifications of theMFGS algorithm uncover the field-and structure-dependency of this imagequality metric. However, MFGS still remains a good choice for determining image quality without a priori knowledge, which is an important characteristic when classifying the huge number of high-resolution images contained in data archives. In addition, this investigation demonstrates that a fast cadence and millisecond exposure times are still insufficient to reach the coherence time of daytime seeing. Nonetheless, the analysis shows that data acquisition rates exceeding 50 Hz are required to capture a substantial fraction of the best seeing moments, significantly boosting the performance of post-facto image restoration.
KW  - Granulation
KW  - Sunspots
KW  - Instrumental effects
KW  - Instrumentation and data management
Y1  - 2018
U6  - https://doi.org/10.1007/s11207-018-1261-1
SN  - 0038-0938
SN  - 1573-093X
VL  - 293
IS  - 3
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Gonzalez Manrique, Sergio Javier
A1  - Kuckein, Christoph
A1  - Collados, M.
A1  - Denker, Carsten
A1  - Solanki, S. K.
A1  - Gomory, P.
A1  - Verma, Meetu
A1  - Balthasar, H.
A1  - Lagg, A.
A1  - Diercke, Andrea
T1  - Temporal evolution of arch filaments as seen in He I 10 830 angstrom
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. We study the evolution of an arch filament system (AFS) and of its individual arch filaments to learn about the processes occurring in them. Methods. We observed the AFS at the GREGOR solar telescope on Tenerife at high cadence with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) in the He I 10 830 angstrom spectral range. The He I triplet profiles were fitted with analytic functions to infer line-of-sight (LOS) velocities to follow plasma motions within the AFS. Results. We tracked the temporal evolution of an individual arch filament over its entire lifetime, as seen in the He I 10 830 angstrom triplet. The arch filament expanded in height and extended in length from 13 ' to 21 '. The lifetime of this arch filament is about 30 min. About 11 min after the arch filament is seen in He I, the loop top starts to rise with an average Doppler velocity of 6 km s(-1). Only two minutes later, plasma drains down with supersonic velocities towards the footpoints reaching a peak velocity of up to 40 km s(-1) in the chromosphere. The temporal evolution of He I 10 830 angstrom profiles near the leading pore showed almost ubiquitous dual red components of the He I triplet, indicating strong downflows, along with material nearly at rest within the same resolution element during the whole observing time.
KW  - Sun: chromosphere
KW  - Sun: activity
KW  - methods: observational
KW  - methods: data analysis
KW  - techniques: high angular resolution
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201832684
SN  - 1432-0746
VL  - 617
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Wutke, Saskia
A1  - Sandoval-Castellanos, Edson
A1  - Benecke, Norbert
A1  - Döhle, Hans-Jürgen
A1  - Friederich, Susanne
A1  - Gonzalez, Javier
A1  - Hofreiter, Michael
A1  - Lougas, Lembi
A1  - Magnell, Ola
A1  - Malaspinas, Anna-Sapfo
A1  - Morales-Muniz, Arturo
A1  - Orlando, Ludovic
A1  - Reissmann, Monika
A1  - Trinks, Alexandra
A1  - Ludwig, Arne
T1  - Decline of genetic diversity in ancient domestic stallions in Europe
JF  - Science Advances
N2  - Present-day domestic horses are immensely diverse in their maternally inherited mitochondrial DNA, yet they show very little variation on their paternally inherited Y chromosome. Although it has recently been shown that Y chromosomal diversity in domestic horses was higher at least until the Iron Age, when and why this diversity disappeared remain controversial questions. We genotyped 16 recently discovered Y chromosomal single-nucleotide polymorphisms in 96 ancient Eurasian stallions spanning the early domestication stages (Copper and Bronze Age) to the Middle Ages. Using this Y chromosomal time series, which covers nearly the entire history of horse domestication, we reveal how Y chromosomal diversity changed over time. Our results also show that the lack of multiple stallion lineages in the extant domestic population is caused by neither a founder effect nor random demographic effects but instead is the result of artificial selection-initially during the Iron Age by nomadic people from the Eurasian steppes and later during the Roman period. Moreover, the modern domestic haplotype probably derived from another, already advantageous, haplotype, most likely after the beginning of the domestication. In line with recent findings indicating that the Przewalski and domestic horse lineages remained connected by gene flow after they diverged about 45,000 years ago, we present evidence for Y chromosomal introgression of Przewalski horses into the gene pool of European domestic horses at least until medieval times.
Y1  - 2018
U6  - https://doi.org/10.1126/sciadv.aap9691
SN  - 2375-2548
VL  - 4
IS  - 4
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Verma, Meetu
A1  - Denker, Carsten
A1  - Balthasar, H.
A1  - Kuckein, Christoph
A1  - Rezaei, R.
A1  - Sobotka, Michal
A1  - Deng, N.
A1  - Wang, Haimin
A1  - Tritschler, A.
A1  - Collados, M.
A1  - Diercke, Andrea
A1  - González Manrique, Sergio Javier
T1  - High-resolution imaging and near-infrared spectroscopy of penumbral decay
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. Combining high-resolution spectropolarimetric and imaging data is key to understanding the decay process of sunspots as it allows us to scrutinize the velocity and magnetic fields of sunspots and their surroundings. Methods. Active region NOAA 12597 was observed on 2016 September 24 with the 1.5-meter GREGOR solar telescope using high-spatial-resolution imaging as well as imaging spectroscopy and near-infrared (NIR) spectropolarimetry. Horizontal proper motions were estimated with local correlation tracking, whereas line-of-sight (LOS) velocities were computed with spectral line fitting methods. The magnetic field properties were inferred with the "Stokes Inversions based on Response functions" (SIR) code for the Si I and Ca I NIR lines. Results. At the time of the GREGOR observations, the leading sunspot had two light bridges indicating the onset of its decay. One of the light bridges disappeared, and an elongated, dark umbral core at its edge appeared in a decaying penumbral sector facing the newly emerging flux. The flow and magnetic field properties of this penumbral sector exhibited weak Evershed flow, moat flow, and horizontal magnetic field. The penumbral gap adjacent to the elongated umbral core and the penumbra in that penumbral sector displayed LOS velocities similar to granulation. The separating polarities of a new flux system interacted with the leading and central part of the already established active region. As a consequence, the leading spot rotated 55 degrees clockwise over 12 h. Conclusions. In the high-resolution observations of a decaying sunspot, the penumbral filaments facing the flux emergence site contained a darkened area resembling an umbral core filled with umbral dots. This umbral core had velocity and magnetic field properties similar to the sunspot umbra. This implies that the horizontal magnetic fields in the decaying penumbra became vertical as observed in flare-induced rapid penumbral decay, but on a very different time-scale.
KW  - Sun: photosphere
KW  - sunspots
KW  - Sun: magnetic fields
KW  - Sun: infrared
KW  - techniques: imaging spectroscopy
KW  - techniques: spectroscopic
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201731801
SN  - 1432-0746
VL  - 614
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Dengler, Jürgen
A1  - Wagner, Viktoria
A1  - Dembicz, Iwona
A1  - Garcia-Mijangos, Itziar
A1  - Naqinezhad, Alireza
A1  - Boch, Steffen
A1  - Chiarucci, Alessandro
A1  - Conradi, Timo
A1  - Filibeck, Goffredo
A1  - Guarino, Riccardo
A1  - Janisova, Monika
A1  - Steinbauer, Manuel J.
A1  - Acic, Svetlana
A1  - Acosta, Alicia T. R.
A1  - Akasaka, Munemitsu
A1  - Allers, Marc-Andre
A1  - Apostolova, Iva
A1  - Axmanova, Irena
A1  - Bakan, Branko
A1  - Baranova, Alina
A1  - Bardy-Durchhalter, Manfred
A1  - Bartha, Sandor
A1  - Baumann, Esther
A1  - Becker, Thomas
A1  - Becker, Ute
A1  - Belonovskaya, Elena
A1  - Bengtsson, Karin
A1  - Benito Alonso, Jose Luis
A1  - Berastegi, Asun
A1  - Bergamini, Ariel
A1  - Bonini, Ilaria
A1  - Bruun, Hans Henrik
A1  - Budzhak, Vasyl
A1  - Bueno, Alvaro
A1  - Antonio Campos, Juan
A1  - Cancellieri, Laura
A1  - Carboni, Marta
A1  - Chocarro, Cristina
A1  - Conti, Luisa
A1  - Czarniecka-Wiera, Marta
A1  - De Frenne, Pieter
A1  - Deak, Balazs
A1  - Didukh, Yakiv P.
A1  - Diekmann, Martin
A1  - Dolnik, Christian
A1  - Dupre, Cecilia
A1  - Ecker, Klaus
A1  - Ermakov, Nikolai
A1  - Erschbamer, Brigitta
A1  - Escudero, Adrian
A1  - Etayo, Javier
A1  - Fajmonova, Zuzana
A1  - Felde, Vivian A.
A1  - Fernandez Calzado, Maria Rosa
A1  - Finckh, Manfred
A1  - Fotiadis, Georgios
A1  - Fracchiolla, Mariano
A1  - Ganeva, Anna
A1  - Garcia-Magro, Daniel
A1  - Gavilan, Rosario G.
A1  - Germany, Markus
A1  - Giladi, Itamar
A1  - Gillet, Francois
A1  - Giusso del Galdo, Gian Pietro
A1  - Gonzalez, Jose M.
A1  - Grytnes, John-Arvid
A1  - Hajek, Michal
A1  - Hajkova, Petra
A1  - Helm, Aveliina
A1  - Herrera, Mercedes
A1  - Hettenbergerova, Eva
A1  - Hobohm, Carsten
A1  - Huellbusch, Elisabeth M.
A1  - Ingerpuu, Nele
A1  - Jandt, Ute
A1  - Jeltsch, Florian
A1  - Jensen, Kai
A1  - Jentsch, Anke
A1  - Jeschke, Michael
A1  - Jimenez-Alfaro, Borja
A1  - Kacki, Zygmunt
A1  - Kakinuma, Kaoru
A1  - Kapfer, Jutta
A1  - Kavgaci, Ali
A1  - Kelemen, Andras
A1  - Kiehl, Kathrin
A1  - Koyama, Asuka
A1  - Koyanagi, Tomoyo F.
A1  - Kozub, Lukasz
A1  - Kuzemko, Anna
A1  - Kyrkjeeide, Magni Olsen
A1  - Landi, Sara
A1  - Langer, Nancy
A1  - Lastrucci, Lorenzo
A1  - Lazzaro, Lorenzo
A1  - Lelli, Chiara
A1  - Leps, Jan
A1  - Loebel, Swantje
A1  - Luzuriaga, Arantzazu L.
A1  - Maccherini, Simona
A1  - Magnes, Martin
A1  - Malicki, Marek
A1  - Marceno, Corrado
A1  - Mardari, Constantin
A1  - Mauchamp, Leslie
A1  - May, Felix
A1  - Michelsen, Ottar
A1  - Mesa, Joaquin Molero
A1  - Molnar, Zsolt
A1  - Moysiyenko, Ivan Y.
A1  - Nakaga, Yuko K.
A1  - Natcheva, Rayna
A1  - Noroozi, Jalil
A1  - Pakeman, Robin J.
A1  - Palpurina, Salza
A1  - Partel, Meelis
A1  - Paetsch, Ricarda
A1  - Pauli, Harald
A1  - Pedashenko, Hristo
A1  - Peet, Robert K.
A1  - Pielech, Remigiusz
A1  - Pipenbaher, Natasa
A1  - Pirini, Chrisoula
A1  - Pleskova, Zuzana
A1  - Polyakova, Mariya A.
A1  - Prentice, Honor C.
A1  - Reinecke, Jennifer
A1  - Reitalu, Triin
A1  - Pilar Rodriguez-Rojo, Maria
A1  - Rolecek, Jan
A1  - Ronkin, Vladimir
A1  - Rosati, Leonardo
A1  - Rosen, Ejvind
A1  - Ruprecht, Eszter
A1  - Rusina, Solvita
A1  - Sabovljevic, Marko
A1  - Maria Sanchez, Ana
A1  - Savchenko, Galina
A1  - Schuhmacher, Oliver
A1  - Skornik, Sonja
A1  - Sperandii, Marta Gaia
A1  - Staniaszek-Kik, Monika
A1  - Stevanovic-Dajic, Zora
A1  - Stock, Marin
A1  - Suchrow, Sigrid
A1  - Sutcliffe, Laura M. E.
A1  - Swacha, Grzegorz
A1  - Sykes, Martin
A1  - Szabo, Anna
A1  - Talebi, Amir
A1  - Tanase, Catalin
A1  - Terzi, Massimo
A1  - Tolgyesi, Csaba
A1  - Torca, Marta
A1  - Torok, Peter
A1  - Tothmeresz, Bela
A1  - Tsarevskaya, Nadezda
A1  - Tsiripidis, Ioannis
A1  - Tzonev, Rossen
A1  - Ushimaru, Atushi
A1  - Valko, Orsolya
A1  - van der Maarel, Eddy
A1  - Vanneste, Thomas
A1  - Vashenyak, Iuliia
A1  - Vassilev, Kiril
A1  - Viciani, Daniele
A1  - Villar, Luis
A1  - Virtanen, Risto
A1  - Kosic, Ivana Vitasovic
A1  - Wang, Yun
A1  - Weiser, Frank
A1  - Went, Julia
A1  - Wesche, Karsten
A1  - White, Hannah
A1  - Winkler, Manuela
A1  - Zaniewski, Piotr T.
A1  - Zhang, Hui
A1  - Ziv, Yaron
A1  - Znamenskiy, Sergey
A1  - Biurrun, Idoia
T1  - GrassPlot - a database of multi-scale plant diversity in Palaearctic grasslands
JF  - Phytocoenologia
N2  - GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). GrassPlot collects plot records (releves) from grasslands and other open habitats of the Palaearctic biogeographic realm. It focuses on precisely delimited plots of eight standard grain sizes (0.0001; 0.001;... 1,000 m(2)) and on nested-plot series with at least four different grain sizes. The usage of GrassPlot is regulated through Bylaws that intend to balance the interests of data contributors and data users. The current version (v. 1.00) contains data for approximately 170,000 plots of different sizes and 2,800 nested-plot series. The key components are richness data and metadata. However, most included datasets also encompass compositional data. About 14,000 plots have near-complete records of terricolous bryophytes and lichens in addition to vascular plants. At present, GrassPlot contains data from 36 countries throughout the Palaearctic, spread across elevational gradients and major grassland types. GrassPlot with its multi-scale and multi-taxon focus complements the larger international vegetationplot databases, such as the European Vegetation Archive (EVA) and the global database " sPlot". Its main aim is to facilitate studies on the scale-and taxon-dependency of biodiversity patterns and drivers along macroecological gradients. GrassPlot is a dynamic database and will expand through new data collection coordinated by the elected Governing Board. We invite researchers with suitable data to join GrassPlot. Researchers with project ideas addressable with GrassPlot data are welcome to submit proposals to the Governing Board.
KW  - biodiversity
KW  - European Vegetation Archive (EVA)
KW  - Eurasian Dry Grassland Group (EDGG)
KW  - grassland vegetation
KW  - GrassPlot
KW  - macroecology
KW  - multi-taxon
KW  - nested plot
KW  - scale-dependence
KW  - species-area relationship (SAR)
KW  - sPlot
KW  - vegetation-plot database
Y1  - 2018
U6  - https://doi.org/10.1127/phyto/2018/0267
SN  - 0340-269X
VL  - 48
IS  - 3
SP  - 331
EP  - 347
PB  - Cramer
CY  - Stuttgart
ER  - 
TY  - THES
A1  - González Manrique, Sergio Javier
T1  - High-Resolution Observations of Emerging Flux Regions
Y1  - 2017
ER  - 
TY  - GEN
A1  - Barlow, Axel
A1  - Hartmann, Stefanie
A1  - Gonzalez, Javier
A1  - Hofreiter, Michael
A1  - Paijmans, Johanna L. A.
T1  - Consensify
BT  - a method for generating pseudohaploid genome sequences from palaeogenomic datasets with reduced error rates
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - A standard practise in palaeogenome analysis is the conversion of mapped short read data into pseudohaploid sequences, frequently by selecting a single high-quality nucleotide at random from the stack of mapped reads. This controls for biases due to differential sequencing coverage, but it does not control for differential rates and types of sequencing error, which are frequently large and variable in datasets obtained from ancient samples. These errors have the potential to distort phylogenetic and population clustering analyses, and to mislead tests of admixture using D statistics. We introduce Consensify, a method for generating pseudohaploid sequences, which controls for biases resulting from differential sequencing coverage while greatly reducing error rates. The error correction is derived directly from the data itself, without the requirement for additional genomic resources or simplifying assumptions such as contemporaneous sampling. For phylogenetic and population clustering analysis, we find that Consensify is less affected by artefacts than methods based on single read sampling. For D statistics, Consensify is more resistant to false positives and appears to be less affected by biases resulting from different laboratory protocols than other frequently used methods. Although Consensify is developed with palaeogenomic data in mind, it is applicable for any low to medium coverage short read datasets. We predict that Consensify will be a useful tool for future studies of palaeogenomes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1033 
KW  - palaeogenomics
KW  - ancient DNA
KW  - sequencing error
KW  - error reduction
KW  - D statistics
KW  - bioinformatics
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-472521
SN  - 1866-8372
IS  - 1033
ER  - 
TY  - JOUR
A1  - Barlow, Axel
A1  - Hartmann, Stefanie
A1  - Gonzalez, Javier
A1  - Hofreiter, Michael
A1  - Paijmans, Johanna L. A.
T1  - Consensify
BT  - a method for generating pseudohaploid genome sequences from palaeogenomic datasets with reduced error rates
JF  - Genes / Molecular Diversity Preservation International
N2  - A standard practise in palaeogenome analysis is the conversion of mapped short read data into pseudohaploid sequences, frequently by selecting a single high-quality nucleotide at random from the stack of mapped reads. This controls for biases due to differential sequencing coverage, but it does not control for differential rates and types of sequencing error, which are frequently large and variable in datasets obtained from ancient samples. These errors have the potential to distort phylogenetic and population clustering analyses, and to mislead tests of admixture using D statistics. We introduce Consensify, a method for generating pseudohaploid sequences, which controls for biases resulting from differential sequencing coverage while greatly reducing error rates. The error correction is derived directly from the data itself, without the requirement for additional genomic resources or simplifying assumptions such as contemporaneous sampling. For phylogenetic and population clustering analysis, we find that Consensify is less affected by artefacts than methods based on single read sampling. For D statistics, Consensify is more resistant to false positives and appears to be less affected by biases resulting from different laboratory protocols than other frequently used methods. Although Consensify is developed with palaeogenomic data in mind, it is applicable for any low to medium coverage short read datasets. We predict that Consensify will be a useful tool for future studies of palaeogenomes.
KW  - palaeogenomics
KW  - ancient DNA
KW  - sequencing error
KW  - error reduction
KW  - D statistics
KW  - bioinformatics
Y1  - 2020
U6  - https://doi.org/10.3390/genes11010050
SN  - 2073-4425
VL  - 11
IS  - 1
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Alberti, Federica
A1  - Gonzalez, Javier
A1  - Paijmans, Johanna L. A.
A1  - Basler, Nikolas
A1  - Preick, Michaela
A1  - Henneberger, Kirstin
A1  - Trinks, Alexandra
A1  - Rabeder, Gernot
A1  - Conard, Nicholas J.
A1  - Muenzel, Susanne C.
A1  - Joger, Ulrich
A1  - Fritsch, Guido
A1  - Hildebrandt, Thomas
A1  - Hofreiter, Michael
A1  - Barlow, Axel
T1  - Optimized DNA sampling of ancient bones using Computed Tomography scans
JF  - Molecular ecology resources
N2  - The prevalence of contaminant microbial DNA in ancient bone samples represents the principal limiting factor for palaeogenomic studies, as it may comprise more than 99% of DNA molecules obtained. Efforts to exclude or reduce this contaminant fraction have been numerous but also variable in their success. Here, we present a simple but highly effective method to increase the relative proportion of endogenous molecules obtained from ancient bones. Using computed tomography (CT) scanning, we identify the densest region of a bone as optimal for sampling. This approach accurately identifies the densest internal regions of petrous bones, which are known to be a source of high-purity ancient DNA. For ancient long bones, CT scans reveal a high-density outermost layer, which has been routinely removed and discarded prior to DNA extraction. For almost all long bones investigated, we find that targeted sampling of this outermost layer provides an increase in endogenous DNA content over that obtained from softer, trabecular bone. This targeted sampling can produce as much as 50-fold increase in the proportion of endogenous DNA, providing a directly proportional reduction in sequencing costs for shotgun sequencing experiments. The observed increases in endogenous DNA proportion are not associated with any reduction in absolute endogenous molecule recovery. Although sampling the outermost layer can result in higher levels of human contamination, some bones were found to have more contamination associated with the internal bone structures. Our method is highly consistent, reproducible and applicable across a wide range of bone types, ages and species. We predict that this discovery will greatly extend the potential to study ancient populations and species in the genomics era.
KW  - ancient DNA
KW  - computer tomography
KW  - palaeogenomics
KW  - paleogenetics
KW  - petrous bone
Y1  - 2018
U6  - https://doi.org/10.1111/1755-0998.12911
SN  - 1755-098X
SN  - 1755-0998
VL  - 18
IS  - 6
SP  - 1196
EP  - 1208
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Gonzalez, Javier
T1  - Phylogenetic position of the most endangered Chilean bird: the Masafuera Rayadito (Aphrastura masafuerae; Furnariidae)
JF  - Tropical conservation science
N2  - Masafuera Rayadito (Aphrastura masafuerae; Furnariidae) is a Critically Endangered species endemic to Alejandro Selkirk Island (Juan Fernandez Archipelago, Chile). Categorized as probably extinct in 1980, later estimates, ranging from 140 (in 2002) to 500 individuals (in 2006-2007), showed a fluctuating population size of the species. The grazing of goats and cattle has increased habitat loss for the species. Other threats are lack of nesting sites, introduced species such as feral cats and rats (Rattus rattus and R. norvegicus), and increased populations of natural predators like the Masafuera Hawk. In order to increase the availability of nesting sites, 81 nest boxes were installed in different habitats in 2006, with evidence of use during subsequent breeding seasons. Despite conservation concerns, however, no genetic studies are yet available for this furnariid. This study reports for the first time the levels of genetic divergence of the species, based on nucleotide sequences of the mitochondrial DNA (cytochrome oxidase subunit 1 gene; COI). Aphrastura masafuerae is closely related to a widespread species of furnariid distributed mainly in Chile on the mainland, the Thorn-tailed Rayadito (A. spinicauda). The Masafuera Rayadito diverged from its mainland sister species probably during the Pleistocene 0.57 +/- 0.19 Myr ago. Consistent with mitochondrial and nuclear molecular clocks, the estimated time of the split between A. masafuerae and A. spinicauda is in perfect agreement with the geological origin of the Juan Fernandez Archipelago, which is of volcanic origin. In order to assess genetic variability within the population of this fragile bird, further studies using a multi-locus genetic approach at the population level are necessary.
KW  - Furnariidae
KW  - Juan Fernandez Archipelago
KW  - mitochondrial DNA
KW  - molecular clock
KW  - Threatened species
Y1  - 2014
SN  - 1940-0829
VL  - 7
IS  - 4
SP  - 677
EP  - 689
PB  - Mongabay.com
CY  - Menlo Park
ER  - 
TY  - JOUR
A1  - Wutke, Saskia
A1  - Benecke, Norbert
A1  - Sandoval-Castellanos, Edson
A1  - Döhle, Hans-Jürgen
A1  - Friederich, Susanne
A1  - Gonzalez Soto, Javier Esteban
A1  - Hallsson, Jon Hallsteinn
A1  - Hofreiter, Michael
A1  - Lougas, Lembi
A1  - Magnell, Ola
A1  - Morales-Muniz, Arturo
A1  - Orlando, Ludovic
A1  - Palsdottir, Albina Hulda
A1  - Reissmann, Monika
A1  - Ruttkay, Matej
A1  - Trinks, Alexandra
A1  - Ludwig, Arne
T1  - Spotted phenotypes in horses lost attractiveness in the Middle Ages
JF  - Scientific reports
N2  - Horses have been valued for their diversity of coat colour since prehistoric times; this is especially the case since their domestication in the Caspian steppe in similar to 3,500 BC. Although we can assume that human preferences were not constant, we have only anecdotal information about how domestic horses were influenced by humans. Our results from genotype analyses show a significant increase in spotted coats in early domestic horses (Copper Age to Iron Age). In contrast, medieval horses carried significantly fewer alleles for these phenotypes, whereas solid phenotypes (i.e., chestnut) became dominant. This shift may have been supported because of (i) pleiotropic disadvantages, (ii) a reduced need to separate domestic horses from their wild counterparts, (iii) a lower religious prestige, or (iv) novel developments in weaponry. These scenarios may have acted alone or in combination. However, the dominance of chestnut is a remarkable feature of the medieval horse population.
Y1  - 2016
U6  - https://doi.org/10.1038/srep38548
SN  - 2045-2322
VL  - 6
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - GEN
A1  - Wutke, Saskia
A1  - Andersson, Leif
A1  - Benecke, Norbert
A1  - Sandoval-Castellanos, Edson
A1  - Gonzalez, Javier
A1  - Hallsson, Jon Hallsteinn
A1  - Lougas, Lembi
A1  - Magnell, Ola
A1  - Morales-Muniz, Arturo
A1  - Orlando, Ludovic
A1  - Palsdottir, Albina Hulda
A1  - Reissmann, Monika
A1  - Munoz-Rodriguez, Mariana B.
A1  - Ruttkay, Matej
A1  - Trinks, Alexandra
A1  - Hofreiter, Michael
A1  - Ludwig, Arne
T1  - The origin of ambling horses
T2  - Current biology
N2  - Horseback riding is the most fundamental use of domestic horses and has had a huge influence on the development of human societies for millennia. Over time, riding techniques and the style of riding improved. Therefore, horses with the ability to perform comfortable gaits (e.g. ambling or pacing), so-called ‘gaited’ horses, have been highly valued by humans, especially for long distance travel. Recently, the causative mutation for gaitedness in horses has been linked to a substitution causing a premature stop codon in the DMRT3 gene (DMRT3_Ser301STOP) [1]. In mice, Dmrt3 is expressed in spinal cord interneurons and plays an important role in the development of limb movement coordination [1]. Genotyping the position in 4396 modern horses from 141 breeds revealed that nowadays the mutated allele is distributed worldwide with an especially high frequency in gaited horses and breeds used for harness racing [2]. Here, we examine historic horse remains for the DMRT3 SNP, tracking the origin of gaitedness to Medieval England between 850 and 900 AD. The presence of the corresponding allele in Icelandic horses (9th–11th century) strongly suggests that ambling horses were brought from the British Isles to Iceland by Norse people. Considering the high frequency of the ambling allele in early Icelandic horses, we believe that Norse settlers selected for this comfortable mode of horse riding soon after arrival. The absence of the allele in samples from continental Europe (including Scandinavia) at this time implies that ambling horses may have spread from Iceland and maybe also the British Isles across the continent at a later date.
Y1  - 2016
U6  - https://doi.org/10.1016/j.cub.2016.07.001
SN  - 0960-9822
SN  - 1879-0445
VL  - 26
SP  - R697
EP  - R699
PB  - Cell Press
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Balthasar, H.
A1  - Gömöry, P.
A1  - González Manrique, Sergio Javier
A1  - Kuckein, Christoph
A1  - Kavka, J.
A1  - Kucera, A.
A1  - Schwartz, P.
A1  - Vaskova, R.
A1  - Berkefeld, T.
A1  - Collados Vera, M.
A1  - Denker, Carsten
A1  - Feller, A.
A1  - Hofmann, A.
A1  - Lagg, A.
A1  - Nicklas, H.
A1  - Suarez, D.
A1  - Pastor Yabar, A.
A1  - Rezaei, R.
A1  - Schlichenmaier, R.
A1  - Schmidt, D.
A1  - Schmidt, W.
A1  - Sigwarth, M.
A1  - Sobotka, M.
A1  - Solanki, S. K.
A1  - Soltau, D.
A1  - Staude, J.
A1  - Strassmeier, Klaus G.
A1  - Volkmer, R.
A1  - von der Lühe, O.
A1  - Waldmann, T.
T1  - Spectropolarimetric observations of an arch filament system with the GREGOR solar telescope
JF  - Astronomische Nachrichten = Astronomical notes
N2  - Arch filament systems occur in active sunspot groups, where a fibril structure connects areas of opposite magnetic polarity, in contrast to active region filaments that follow the polarity inversion line. We used the GREGOR Infrared Spectrograph (GRIS) to obtain the full Stokes vector in the spectral lines SiI lambda 1082.7 nm, He I lambda 1083.0 nm, and Ca I lambda 1083.9 nm. We focus on the near-infrared calcium line to investigate the photospheric magnetic field and velocities, and use the line core intensities and velocities of the helium line to study the chromospheric plasma. The individual fibrils of the arch filament system connect the sunspot with patches of magnetic polarity opposite to that of the spot. These patches do not necessarily coincide with pores, where the magnetic field is strongest. Instead, areas are preferred not far from the polarity inversion line. These areas exhibit photospheric downflows of moderate velocity, but significantly higher downflows of up to 30 km s(-1) in the chromospheric helium line. Our findings can be explained with new emerging flux where the matter flows downward along the field lines of rising flux tubes, in agreement with earlier results. (C) 2016 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim
KW  - Sun: filaments
KW  - Sun: photosphere
KW  - techniques: polarimetric
KW  - techniques: spectroscopic
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612432
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1050
EP  - 1056
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Denker, Carsten
A1  - Heibel, C.
A1  - Rendtel, J.
A1  - Arlt, K.
A1  - Balthasar, H.
A1  - Diercke, Andrea
A1  - Gonzalez Manrique, Sergio Javier
A1  - Hofmann, A.
A1  - Kuckein, Christoph
A1  - Önel, H.
A1  - Valliappan, Senthamizh Pavai
A1  - Staude, J.
A1  - Verma, Meetu
T1  - Solar physics at the Einstein Tower
JF  - Astronomische Nachrichten = Astronomical notes
KW  - history and philosophy of astronomy
KW  - Sun: photosphere
KW  - Sun: magnetic fields
KW  - techniques: spectroscopic
KW  - telescopes
Y1  - 2016
U6  - https://doi.org/10.1002/asna.201612442
SN  - 0004-6337
SN  - 1521-3994
VL  - 337
SP  - 1105
EP  - 1113
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kuckein, Christoph
A1  - Diercke, Andrea
A1  - González Manrique, Sergio Javier
A1  - Verma, Meetu
A1  - Loehner-Boettcher, Johannes
A1  - Socas-Navarro, H.
A1  - Balthasar, Horst
A1  - Sobotka, M.
A1  - Denker, Carsten
T1  - Ca II 8542 angstrom brightenings induced by a solar microflare
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. We study small-scale brightenings in Ca II 8542 angstrom line-core images to determine their nature and effect on localized heating and mass transfer in active regions. Methods. High-resolution two-dimensional spectroscopic observations of a solar active region in the near-infrared Ca II 8542 angstrom line were acquired with the GREGOR Fabry-Perot Interferometer attached to the 1.5-m GREGOR telescope. Inversions of the spectra were carried out using the NICOLE code to infer temperatures and line-of-sight (LOS) velocities. Response functions of the Ca II line were computed for temperature and LOS velocity variations. Filtergrams of the Atmospheric Imaging Assembly (AIA) and magnetograms of the Helioseismic and Magnetic Imager (HMI) were coaligned to match the ground-based observations and to follow the Ca II brightenings along all available layers of the atmosphere. Results. We identified three brightenings of sizes up to 2 ' x 2 ' that appeared in the Ca II 8542 angstrom line-core images. Their lifetimes were at least 1.5 min. We found evidence that the brightenings belonged to the footpoints of a microflare (MF). The properties of the observed brightenings disqualified the scenarios of Ellerman bombs or Interface Region Imaging Spectrograph (IRIS) bombs. However, this MF shared some common properties with flaring active-region fibrils or flaring arch filaments (FAFs): (1) FAFs and MFs are both apparent in chromospheric and coronal layers according to the AIA channels; and (2) both show flaring arches with lifetimes of about 3.0-3.5 min and lengths of similar to 20 ' next to the brightenings. The inversions revealed heating by 600 K at the footpoint location in the ambient chromosphere during the impulsive phase. Connecting the footpoints, a dark filamentary structure appeared in the Ca II line-core images. Before the start of the MF, the spectra of this structure already indicated average blueshifts, meaning upward motions of the plasma along the LOS. During the impulsive phase, these velocities increased up to -2.2 km s(-1). The structure did not disappear during the observations. Downflows dominated at the footpoints. However, in the upper photosphere, slight upflows occurred during the impulsive phase. Hence, bidirectional flows are present in the footpoints of the MF.
KW  - Sun: photosphere
KW  - Sun: chromosphere
KW  - Sun: corona
KW  - Sun: activity
KW  - techniques: imaging spectroscopy
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201731319
SN  - 1432-0746
VL  - 608
PB  - EDP Sciences
CY  - Les Ulis
ER  -