TY  - JOUR
A1  - Dineva, Ekaterina
A1  - Pearson, Jeniveve
A1  - Ilyin, Ilya
A1  - Verma, Meetu
A1  - Diercke, Andrea
A1  - Strassmeier, Klaus
A1  - Denker, Carsten
T1  - Characterization of chromospheric activity based on Sun-as-a-star spectral and disk-resolved activity indices
JF  - Astronomische Nachrichten = Astronomical notes
N2  - The strong chromospheric absorption lines Ca ii H & K are tightly connected to stellar surface magnetic fields. Only for the Sun, spectral activity indices can be related to evolving magnetic features on the solar disk. The Solar Disk-Integrated (SDI) telescope feeds the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) of the Large Binocular Telescope (LBT) at Mt. Graham International Observatory, Arizona, U.S.A. We present high-resolution, high-fidelity spectra that were recorded on 184 & 82 days in 2018 & 2019 and derive the Ca ii H & K emission ratio, that is, the S-index. In addition, we compile excess brightness and area indices based on full-disk Ca ii K-line-core filtergrams of the Chromospheric Telescope (ChroTel) at Observatorio del Teide, Tenerife, Spain and full-disk ultraviolet (UV) 1600 angstrom images of the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Thus, Sun-as-a-star spectral indices are related to their counterparts derived from resolved images of the solar chromosphere. All indices display signatures of rotational modulation, even during the very low magnetic activity in the minimum of Solar Cycle 24. Bringing together different types of activity indices has the potential to join disparate chromospheric datasets yielding a comprehensive description of chromospheric activity across many solar cycles.
KW  - astronomical databases
KW  - miscellaneous
KW  - methods
KW  - data analysis
KW  - activity
KW  - Sun
KW  - atmosphere
KW  - chromosphere
KW  - techniques
KW  - spectroscopic
Y1  - 2022
U6  - https://doi.org/10.1002/asna.20223996
SN  - 0004-6337
SN  - 1521-3994
VL  - 343
IS  - 5
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
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  -