TY  - JOUR
A1  - Dineva, Ekaterina Ivanova
A1  - Verma, Meetu
A1  - Gonzalez Manrique, Sergio Javier
A1  - Schwartz, Pavol
A1  - Denker, Carsten
T1  - Cloud model inversions of strong chromospheric absorption lines using principal component analysis
JF  - Astronomische Nachrichten = Astronomical notes
N2  - High-resolution spectroscopy of strong chromospheric absorption lines delivers nowadays several millions of spectra per observing day, when using fast scanning devices to cover large regions on the solar surface. Therefore, fast and robust inversion schemes are needed to explore the large data volume. Cloud model (CM) inversions of the chromospheric H alpha line are commonly employed to investigate various solar features including filaments, prominences, surges, jets, mottles, and (macro-) spicules. The choice of the CM was governed by its intuitive description of complex chromospheric structures as clouds suspended above the solar surface by magnetic fields. This study is based on observations of active region NOAA 11126 in H alpha, which were obtained November 18-23, 2010 with the echelle spectrograph of the vacuum tower telescope at the Observatorio del Teide, Spain. Principal component analysis reduces the dimensionality of spectra and conditions noise-stripped spectra for CM inversions. Modeled H alpha intensity and contrast profiles as well as CM parameters are collected in a database, which facilitates efficient processing of the observed spectra. Physical maps are computed representing the line-core and continuum intensity, absolute contrast, equivalent width, and Doppler velocities, among others. Noise-free spectra expedite the analysis of bisectors. The data processing is evaluated in the context of "big data," in particular with respect to automatic classification of spectra.
KW  - sun
KW  - activity - sun
KW  - atmosphere - sun
KW  - chromosphere - methods
KW  - data
KW  - analysis - techniques
KW  - spectroscopic - astronomical databases
KW  - miscellaneous
Y1  - 2020
U6  - https://doi.org/10.1002/asna.202013652
SN  - 0004-6337
SN  - 1521-3994
VL  - 341
IS  - 1
SP  - 64
EP  - 78
PB  - Wiley-VCH Verl.
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Gömöry, Peter
A1  - Balthasar, Horst
A1  - Kuckein, Christoph
A1  - Koza, Julis
A1  - Veronig, Astrid M.
A1  - González Manrique, Sergio Javier
A1  - Kucera, Ales
A1  - Schwartz, Pavol
A1  - Hanslmeier, Arnold
T1  - Flare-induced changes of the photospheric magnetic field in a delta-spot deduced from ground-based observations
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. Changes of the magnetic field and the line-of-sight velocities in the photosphere are being reported for an M-class flare that originated at a delta-spot belonging to active region NOAA 11865. Methods. High-resolution ground-based near-infrared spectropolarimetric observations were acquired simultaneously in two photospheric spectral lines, Fe I 10783 angstrom and Si I 10786 angstrom, with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope (VTT) in Tenerife on 2013 October 15. The observations covered several stages of the M-class flare. Inversions of the full-Stokes vector of both lines were carried out and the results were put into context using (extreme)-ultraviolet filtergrams from the Solar Dynamics Observatory (SDO). Results. The active region showed high flaring activity during the whole observing period. After the M-class flare, the longitudinal magnetic field did not show significant changes along the polarity inversion line (PIL). However, an enhancement of the transverse magnetic field of approximately 550G was found that bridges the PIL and connects umbrae of opposite polarities in the delta-spot. At the same time, a newly formed system of loops appeared co-spatially in the corona as seen in 171 angstrom filtergrams of the Atmospheric Imaging Assembly (AIA) on board SDO. However, we cannot exclude that the magnetic connection between the umbrae already existed in the upper atmosphere before the M-class flare and became visible only later when it was filled with hot plasma. The photospheric Doppler velocities show a persistent upflow pattern along the PIL without significant changes due to the flare. Conclusions. The increase of the transverse component of the magnetic field after the flare together with the newly formed loop system in the corona support recent predictions of flare models and flare observations.
KW  - Sun: magnetic fields
KW  - sunspots
KW  - Sun: photosphere
KW  - Sun: flares
KW  - techniques: polarimetric
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201730644
SN  - 1432-0746
VL  - 602
SP  - 14
EP  - 27
PB  - EDP Sciences
CY  - Les Ulis
ER  -