Feller, Alex

[["dc.bibliographiccitation.firstpage","1050"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Astronomische Nachrichten"],["dc.bibliographiccitation.lastpage","1056"],["dc.bibliographiccitation.volume","337"],["dc.contributor.author","Balthasar, H."],["dc.contributor.author","Gomory, P."],["dc.contributor.author","Manrique, S. J. Gonzalez"],["dc.contributor.author","Kuckein, C."],["dc.contributor.author","Kavka, J."],["dc.contributor.author","Kucera, A."],["dc.contributor.author","Schwartz, P."],["dc.contributor.author","Vaskova, R."],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Collados Vera, M."],["dc.contributor.author","Denker, C."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Hofmann, Albrecht W."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Nicklas, H."],["dc.contributor.author","Suarez, D."],["dc.contributor.author","Pastor Yabar, A."],["dc.contributor.author","Rezaei, R."],["dc.contributor.author","Schlichenmaier, R."],["dc.contributor.author","Schmidt, D."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Sigwarth, M."],["dc.contributor.author","Sobotka, M."],["dc.contributor.author","Solanki, Parth K."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Staude, J."],["dc.contributor.author","Strassmeier, K. G."],["dc.contributor.author","Volkmer, R."],["dc.contributor.author","von der Luhe, O."],["dc.contributor.author","Waldmann, T."],["dc.date.accessioned","2018-11-07T10:06:05Z"],["dc.date.available","2018-11-07T10:06:05Z"],["dc.date.issued","2016"],["dc.description.abstract","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"],["dc.identifier.doi","10.1002/asna.201612432"],["dc.identifier.isi","000391297900010"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39025"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.publisher.place","Weinheim"],["dc.relation.conference","12th Potsdam Thinkshop Conference on Dynamic Sun - Exploring the Many Facets of Solar Eruptive Events"],["dc.relation.eventlocation","Potsdam, GERMANY"],["dc.relation.issn","1521-3994"],["dc.relation.issn","0004-6337"],["dc.title","Spectropolarimetric observations of an arch filament system with the GREGOR solar telescope"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A4"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","596"],["dc.contributor.author","Franz, M."],["dc.contributor.author","Collados, M."],["dc.contributor.author","Bethge, C."],["dc.contributor.author","Schlichenmaier, R."],["dc.contributor.author","Borrero, J. M."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Solanki, S. K."],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Kiess, C."],["dc.contributor.author","Rezaei, R."],["dc.contributor.author","Schmidt, Christian D."],["dc.contributor.author","Sigwarth, M."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Volkmer, R."],["dc.contributor.author","Luhe, O. von der"],["dc.contributor.author","Waldmann, T."],["dc.contributor.author","Orozco, D."],["dc.contributor.author","Pastor Yabar, A."],["dc.contributor.author","Denker, C."],["dc.contributor.author","Balthasar, H."],["dc.contributor.author","Staude, J."],["dc.contributor.author","Hofmann, A."],["dc.contributor.author","Strassmeier, K."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Nicklas, H."],["dc.contributor.author","Kneer, F."],["dc.contributor.author","Sobotka, M."],["dc.date.accessioned","2020-07-01T07:16:29Z"],["dc.date.available","2020-07-01T07:16:29Z"],["dc.date.issued","2016"],["dc.description.abstract","Context. A significant part of the penumbral magnetic field returns below the surface in the very deep photosphere. For lines in the visible, a large portion of this return field can only be detected indirectly by studying its imprints on strongly asymmetric and three-lobed Stokes V profiles. Infrared lines probe a narrow layer in the very deep photosphere, providing the possibility of directly measuring the orientation of magnetic fields close to the solar surface. Aims. We study the topology of the penumbral magnetic field in the lower photosphere, focusing on regions where it returns below the surface. Methods. We analyzed 71 spectropolarimetric datasets from Hinode and from the GREGOR infrared spectrograph. We inferred the quality and polarimetric accuracy of the infrared data after applying several reduction steps. Techniques of spectral inversion and forward synthesis were used to test the detection algorithm. We compared the morphology and the fractional penumbral area covered by reversed-polarity and three-lobed Stokes V profiles for sunspots at disk center. We determined the amount of reversed-polarity and three-lobed Stokes V profiles in visible and infrared data of sunspots at various heliocentric angles. From the results, we computed center-to-limb variation curves, which were interpreted in the context of existing penumbral models. Results. Observations in visible and near-infrared spectral lines yield a significant difference in the penumbral area covered by magnetic fields of opposite polarity. In the infrared, the number of reversed-polarity Stokes V profiles is smaller by a factor of two than in the visible. For three-lobed Stokes V profiles the numbers differ by up to an order of magnitude."],["dc.identifier.arxiv","1608.00513v2"],["dc.identifier.doi","10.1051/0004-6361/201628407"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/66810"],["dc.language.iso","en"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","Magnetic fields of opposite polarity in sunspot penumbrae"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","2"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","The Astrophysical Journal Supplement Series"],["dc.bibliographiccitation.volume","229"],["dc.contributor.author","Solanki, Parth K."],["dc.contributor.author","Riethmueller, T. L."],["dc.contributor.author","Barthol, P."],["dc.contributor.author","Danilovic, S."],["dc.contributor.author","Deutsch, W."],["dc.contributor.author","Doerr, H.-P."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Gandorfer, A."],["dc.contributor.author","Germerott, D."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Grauf, B."],["dc.contributor.author","Heerlein, K."],["dc.contributor.author","Hirzberger, J."],["dc.contributor.author","Kolleck, M."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Meller, R."],["dc.contributor.author","Tomasch, G."],["dc.contributor.author","van Noort, M."],["dc.contributor.author","Blanco Rodriguez, J."],["dc.contributor.author","Gasent Blesa, J. L."],["dc.contributor.author","Balaguer Jimenez, M."],["dc.contributor.author","Del Toro Iniesta, J. C."],["dc.contributor.author","Lopez Jimenez, A. C."],["dc.contributor.author","Orozco Suarez, D."],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Halbgewachs, C."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Alvarez-Herrero, A."],["dc.contributor.author","Sabau-Graziati, L."],["dc.contributor.author","Perez Grande, I."],["dc.contributor.author","Pillet, V. Martinez"],["dc.contributor.author","Card, G."],["dc.contributor.author","Centeno, R."],["dc.contributor.author","Knoelker, M."],["dc.contributor.author","Lecinski, A."],["dc.date.accessioned","2018-11-07T10:26:56Z"],["dc.date.available","2018-11-07T10:26:56Z"],["dc.date.issued","2017"],["dc.description.abstract","The SUNRISE balloon-borne solar observatory, consisting of a 1 m aperture telescope that provides a stabilized image to a UV filter imager and an imaging vector polarimeter, carried out its second science flight in 2013 June. It provided observations of parts of active regions at high spatial resolution, including the first high-resolution images in the Mg II. k line. The obtained data are of very high quality, with the best UV images reaching the diffraction limit of the telescope at 3000 angstrom after Multi-Frame Blind Deconvolution reconstruction accounting for phasediversity information. Here a brief update is given of the instruments and the data reduction techniques, which includes an inversion of the polarimetric data. Mainly those aspects that evolved compared with the first flight are described. A tabular overview of the observations is given. In addition, an example time series of a part of the emerging active region NOAA AR. 11768 observed relatively close to disk center is described and discussed in some detail. The observations cover the pores in the trailing polarity of the active region, as well as the polarity inversion line where flux emergence was ongoing and a small flare-like brightening occurred in the course of the time series. The pores are found to contain magnetic field strengths ranging up to 2500 G, and while large pores are clearly darker and cooler than the quiet Sun in all layers of the photosphere, the temperature and brightness of small pores approach or even exceed those of the quiet Sun in the upper photosphere."],["dc.identifier.doi","10.3847/1538-4365/229/1/2"],["dc.identifier.isi","000397557300002"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43145"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.publisher","Iop Publishing Ltd"],["dc.relation.issn","1538-4365"],["dc.relation.issn","0067-0049"],["dc.title","The Second Flight of the SUNRISE Balloon-borne Solar Observatory: Overview of Instrument Updates, the Flight, the Data, and First Results"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A2"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","596"],["dc.contributor.author","Borrero, J. M."],["dc.contributor.author","Asensio Ramos, A."],["dc.contributor.author","Collados, M."],["dc.contributor.author","Schlichenmaier, R."],["dc.contributor.author","Balthasar, H."],["dc.contributor.author","Franz, M."],["dc.contributor.author","Rezaei, R."],["dc.contributor.author","Kiess, C."],["dc.contributor.author","Orozco Suarez, D."],["dc.contributor.author","Pastor, A."],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","von der Luehe, O."],["dc.contributor.author","Schmidt, D."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Sigwarth, M."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Volkmer, R."],["dc.contributor.author","Waldmann, T."],["dc.contributor.author","Denker, C."],["dc.contributor.author","Hofmann, Albrecht W."],["dc.contributor.author","Staude, J."],["dc.contributor.author","Strassmeier, K. G."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Solanki, Parth K."],["dc.contributor.author","Sobotka, M."],["dc.contributor.author","Nicklas, H."],["dc.date.accessioned","2018-11-07T10:04:58Z"],["dc.date.available","2018-11-07T10:04:58Z"],["dc.date.issued","2016"],["dc.description.abstract","Context. Some models for the topology of the magnetic field in sunspot penumbrae predict regions free of magnetic fields or with only dynamically weak fields in the deep photosphere. Aims. We aim to confirm or refute the existence of weak-field regions in the deepest photospheric layers of the penumbra. Methods. We investigated the magnetic field at log tau(5) = 0 is by inverting spectropolarimetric data of two different sunspots located very close to disk center with a spatial resolution of approximately 0.4-0.45 ''. The data have been recorded using the GRIS instrument attached to the 1.5-m solar telescope GREGOR at the El Teide observatory. The data include three Fe I lines around 1565 nm, whose sensitivity to the magnetic field peaks half a pressure scale height deeper than the sensitivity of the widely used Fe I spectral line pair at 630 nm. Before the inversion, the data were corrected for the effects of scattered light using a deconvolution method with several point spread functions. Results. At log tau(5) = 0 we find no evidence of regions with dynamically weak (B < 500 Gauss) magnetic fields in sunspot penumbrae. This result is much more reliable than previous investigations made on Fe I lines at 630 nm. Moreover, the result is independent of the number of nodes employed in the inversion, is independent of the point spread function used to deconvolve the data, and does not depend on the amount of stray light (i.e., wide-angle scattered light) considered."],["dc.identifier.doi","10.1051/0004-6361/201628313"],["dc.identifier.isi","000390797900033"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14275"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/38805"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","28"],["dc.bibliographiccitation.issue","S327"],["dc.bibliographiccitation.journal","Proceedings of the International Astronomical Union"],["dc.bibliographiccitation.lastpage","33"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Manrique, S. J. González"],["dc.contributor.author","Denker, C."],["dc.contributor.author","Kuckein, C."],["dc.contributor.author","Yabar, A. Pastor"],["dc.contributor.author","Collados, M."],["dc.contributor.author","Verma, M."],["dc.contributor.author","Balthasar, H."],["dc.contributor.author","Diercke, A."],["dc.contributor.author","Fischer, C. E."],["dc.contributor.author","Gömöry, P."],["dc.contributor.author","González, N. Bello"],["dc.contributor.author","Schlichenmaier, R."],["dc.contributor.author","Armas, M. Cubas"],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Hoch, S."],["dc.contributor.author","Hofmann, A."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Nicklas, H."],["dc.contributor.author","Suárez, D. Orozco"],["dc.contributor.author","Schmidt, D."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Sigwarth, M."],["dc.contributor.author","Sobotka, M."],["dc.contributor.author","Solanki, S. K."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Staude, J."],["dc.contributor.author","Strassmeier, K. G."],["dc.contributor.author","Volkmer, R."],["dc.contributor.author","von der Lühe, O."],["dc.contributor.author","Waldmann, T."],["dc.date.accessioned","2020-12-10T15:22:25Z"],["dc.date.available","2020-12-10T15:22:25Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1017/S1743921317000278"],["dc.identifier.eissn","1743-9221"],["dc.identifier.issn","1743-9213"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/73394"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Flows along arch filaments observed in the GRIS ‘very fast spectroscopic mode’"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A3"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","596"],["dc.contributor.author","Verma, M."],["dc.contributor.author","Denker, C."],["dc.contributor.author","Balthasar, H."],["dc.contributor.author","Kuckein, C."],["dc.contributor.author","Manrique, S. J. Gonzalez"],["dc.contributor.author","Sobotka, M."],["dc.contributor.author","Gonzalez, N. Bello"],["dc.contributor.author","Hoch, S."],["dc.contributor.author","Diercke, A."],["dc.contributor.author","Kummerow, P."],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Collados, M."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Hofmann, Albrecht W."],["dc.contributor.author","Kneer, F."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Loehner-Boettcher, J."],["dc.contributor.author","Nicklas, H."],["dc.contributor.author","Pastor Yabar, A."],["dc.contributor.author","Schlichenmaier, R."],["dc.contributor.author","Schmidt, D."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Schubert, M."],["dc.contributor.author","Sigwarth, M."],["dc.contributor.author","Solanki, Parth K."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Staude, J."],["dc.contributor.author","Strassmeier, K. G."],["dc.contributor.author","Volkmer, R."],["dc.contributor.author","von der Luehe, O."],["dc.contributor.author","Waldmann, T."],["dc.date.accessioned","2018-11-07T10:04:59Z"],["dc.date.available","2018-11-07T10:04:59Z"],["dc.date.issued","2016"],["dc.description.abstract","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."],["dc.identifier.doi","10.1051/0004-6361/201628380"],["dc.identifier.isi","000390797900035"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14276"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/38807"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/312495/EU/High-Resolution Solar Physics Network/SOLARNET"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Horizontal flow fields in and around a small active region The transition period between flux emergence and decay"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A8"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","596"],["dc.contributor.author","Joshi, J."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Solanki, S. K."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Collados, M."],["dc.contributor.author","Orozco Suárez, D."],["dc.contributor.author","Schlichenmaier, R."],["dc.contributor.author","Franz, M."],["dc.contributor.author","Balthasar, H."],["dc.contributor.author","Denker, C."],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Hofmann, A."],["dc.contributor.author","Kiess, C."],["dc.contributor.author","Nicklas, H."],["dc.contributor.author","Pastor Yabar, A."],["dc.contributor.author","Rezaei, R."],["dc.contributor.author","Schmidt, D."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Sobotka, M."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Staude, J."],["dc.contributor.author","Strassmeier, K. G."],["dc.contributor.author","Volkmer, R."],["dc.contributor.author","von der Lühe, O."],["dc.contributor.author","Waldmann, T."],["dc.date.accessioned","2019-07-09T11:43:08Z"],["dc.date.available","2019-07-09T11:43:08Z"],["dc.date.issued","2016"],["dc.description.abstract","Aims. The fine-structure of the magnetic field in a sunspot penumbra in the upper chromosphere is to be explored and compared to that in the photosphere. Methods. Spectropolarimetric observations with high spatial resolution were recorded with the 1.5-m GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The observed spectral domain includes the upper chromospheric Hei triplet at 10 830 Å  and the photospheric Sii 10 827.1 Å  and Cai 10 833.4 Å  spectral lines. The upper chromospheric magnetic field is obtained by inverting the Hei triplet assuming a Milne-Eddington-type model atmosphere. A height-dependent inversion was applied to the Sii 10 827.1 Å  and Cai 10 833.4 Å  lines to obtain the photospheric magnetic field. Results. We find that the inclination of the magnetic field varies in the azimuthal direction in the photosphere and in the upper chromosphere. The chromospheric variations coincide remarkably well with the variations in the inclination of the photospheric field and resemble the well-known spine and interspine structure in the photospheric layers of penumbrae. The typical peak-to-peak variations in the inclination of the magnetic field in the upper chromosphere are found to be 10°–15°, which is roughly half the variation in the photosphere. In contrast, the magnetic field strength of the observed penumbra does not vary on small spatial scales in the upper chromosphere. Conclusions. Thanks to the high spatial resolution of the observations that is possible with the GREGOR telescope at 1.08 microns, we find that the prominent small-scale fluctuations in the magnetic field inclination, which are a salient part of the property of sunspot penumbral photospheres, also persist in the chromosphere, although at somewhat reduced amplitudes. Such a complex magnetic configuration may facilitate penumbral chromospheric dynamic phenomena, such as penumbral micro-jets or transient bright dots."],["dc.identifier.doi","10.1051/0004-6361/201629214"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14289"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/58836"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/312495/EU/High-Resolution Solar Physics Network/SOLARNET"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Upper chromospheric magnetic field of a sunspot penumbra: observations of fine structure"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","35"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Solar Physics"],["dc.bibliographiccitation.lastpage","55"],["dc.bibliographiccitation.volume","268"],["dc.contributor.author","Gandorfer, A."],["dc.contributor.author","Grauf, B."],["dc.contributor.author","Barthol, P."],["dc.contributor.author","Riethmueller, T. L."],["dc.contributor.author","Solanki, Parth K."],["dc.contributor.author","Chares, Bernd"],["dc.contributor.author","Deutsch, W."],["dc.contributor.author","Ebert, Sandra"],["dc.contributor.author","Feller, A."],["dc.contributor.author","Germerott, D."],["dc.contributor.author","Heerlein, K."],["dc.contributor.author","Heinrichs, Jochen"],["dc.contributor.author","Hirche, D."],["dc.contributor.author","Hirzberger, J."],["dc.contributor.author","Kolleck, M."],["dc.contributor.author","Meller, R."],["dc.contributor.author","Mueller, R."],["dc.contributor.author","Schaefer, R."],["dc.contributor.author","Tomasch, G."],["dc.contributor.author","Knoelker, M."],["dc.contributor.author","Martinez Pillet, V."],["dc.contributor.author","Bonet, J. A."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Feger, B."],["dc.contributor.author","Heidecke, F."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Tischenberg, A."],["dc.contributor.author","Fischer, A."],["dc.contributor.author","Title, A."],["dc.contributor.author","Anwand, H."],["dc.contributor.author","Schmidt, E."],["dc.date.accessioned","2018-11-07T09:02:03Z"],["dc.date.available","2018-11-07T09:02:03Z"],["dc.date.issued","2011"],["dc.description.abstract","We describe the design of the Sunrise Filter Imager (SuFI) and the Image Stabilization and Light Distribution (ISLiD) unit onboard the Sunrise balloon borne solar observatory. This contribution provides the necessary information which is relevant to understand the instruments' working principles, the relevant technical data, and the necessary information about calibration issues directly related to the science data."],["dc.identifier.doi","10.1007/s11207-010-9636-y"],["dc.identifier.isi","000285364400002"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/5990"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/24584"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","0038-0938"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","Goescholar"],["dc.rights.uri","https://goedoc.uni-goettingen.de/licenses"],["dc.title","The Filter Imager SuFI and the Image Stabilization and Light Distribution System ISLiD of the Sunrise Balloon-Borne Observatory: Instrument Description"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1057"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Astronomische Nachrichten"],["dc.bibliographiccitation.lastpage","1063"],["dc.bibliographiccitation.volume","337"],["dc.contributor.author","Manrique, S. J. Gonzalez"],["dc.contributor.author","Kuckein, C."],["dc.contributor.author","Pastor Yabar, A."],["dc.contributor.author","Collados, M."],["dc.contributor.author","Denker, C."],["dc.contributor.author","Fischer, C. E."],["dc.contributor.author","Gomory, P."],["dc.contributor.author","Diercke, A."],["dc.contributor.author","Gonzalez, N. Bello"],["dc.contributor.author","Schlichenmaier, R."],["dc.contributor.author","Balthasar, H."],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Hoch, S."],["dc.contributor.author","Hofmann, Albrecht W."],["dc.contributor.author","Kneer, F."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Nicklas, H."],["dc.contributor.author","Orozco Suarez, D."],["dc.contributor.author","Schmidt, D."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Sigwarth, M."],["dc.contributor.author","Sobotka, M."],["dc.contributor.author","Solanki, Parth K."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Staude, J."],["dc.contributor.author","Strassmeier, K. G."],["dc.contributor.author","Verma, M."],["dc.contributor.author","Volkmer, R."],["dc.contributor.author","von der Luhe, O."],["dc.contributor.author","Waldmann, T."],["dc.date.accessioned","2018-11-07T10:06:06Z"],["dc.date.available","2018-11-07T10:06:06Z"],["dc.date.issued","2016"],["dc.description.abstract","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"],["dc.identifier.doi","10.1002/asna.201512433"],["dc.identifier.isi","000391297900011"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39026"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.publisher.place","Weinheim"],["dc.relation.conference","12th Potsdam Thinkshop Conference on Dynamic Sun - Exploring the Many Facets of Solar Eruptive Events"],["dc.relation.eventlocation","Potsdam, GERMANY"],["dc.relation.issn","1521-3994"],["dc.relation.issn","0004-6337"],["dc.title","Fitting peculiar spectral profiles in He I 10830 angstrom absorption features"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1090"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Astronomische Nachrichten"],["dc.bibliographiccitation.lastpage","1098"],["dc.bibliographiccitation.volume","337"],["dc.contributor.author","Verma, M."],["dc.contributor.author","Denker, C."],["dc.contributor.author","Boehm, F."],["dc.contributor.author","Balthasar, H."],["dc.contributor.author","Fischer, C. E."],["dc.contributor.author","Kuckein, C."],["dc.contributor.author","Gonzalez, N. Bello"],["dc.contributor.author","Berkefeld, T."],["dc.contributor.author","Collados, M."],["dc.contributor.author","Diercke, A."],["dc.contributor.author","Feller, A."],["dc.contributor.author","Manrique, S. J. Gonzalez"],["dc.contributor.author","Hofmann, Albrecht W."],["dc.contributor.author","Lagg, A."],["dc.contributor.author","Nicklas, H."],["dc.contributor.author","Orozco Suarez, D."],["dc.contributor.author","Pator Yabar, A."],["dc.contributor.author","Rezaei, R."],["dc.contributor.author","Schlichenmaier, R."],["dc.contributor.author","Schmidt, D."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Sigwarth, M."],["dc.contributor.author","Sobotka, M."],["dc.contributor.author","Solanki, Parth K."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Staude, J."],["dc.contributor.author","Strassmeier, K. G."],["dc.contributor.author","Volkmer, R."],["dc.contributor.author","von der Luhe, O."],["dc.contributor.author","Waldmann, T."],["dc.date.accessioned","2018-11-07T10:06:06Z"],["dc.date.available","2018-11-07T10:06:06Z"],["dc.date.issued","2016"],["dc.description.abstract","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"],["dc.identifier.doi","10.1002/asna.201612447"],["dc.identifier.isi","000391297900016"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39027"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-v C H Verlag Gmbh"],["dc.publisher.place","Weinheim"],["dc.relation.conference","12th Potsdam Thinkshop Conference on Dynamic Sun - Exploring the Many Facets of Solar Eruptive Events"],["dc.relation.eventlocation","Potsdam, GERMANY"],["dc.relation.issn","1521-3994"],["dc.relation.issn","0004-6337"],["dc.title","Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]