Results 21 to 30 of about 860 (219)
Photospheric and chromospheric activity in four young solar-type stars [PDF]
The Astrophysical Journal, 2006 We present a photometric and spectroscopic study of four G-K dwarfs, namely HD 166, epsilon Eri, chi1 Ori and kappa1 Cet. In three cases, we find a clear spatial association between photospheric and chromospheric active regions. For chi1 Ori we do not find appreciable variations of photospheric temperature, and chromospheric Halpha emission. We applied
Biazzo, Katia +4 more
openaire +3 more sources
Heating of the solar chromosphere through current dissipation
, 2022 Context. The solar chromosphere is heated to temperatures higher than predicted by radiative equilibrium. This excess heating is greater in active regions where the magnetic field is stronger. Aims: We aim to investigate the magnetic topology associated
Leenaarts, J. +7 more
core +2 more sources
The Solar Twin Planet Search [PDF]
Astronomy & Astrophysics, 2018 Context. It is well known that the magnetic activity of solar-type stars decreases with age, but it is widely debated in the literature whether there is a smooth decline or if there is an early sharp drop until 1–2 Gyr that is followed by a relatively inactive constant phase. Aims.
Diego Lorenzo-Oliveira +10 more
openaire +3 more sources
The Astrophysical Journal, 2023 High-resolution spectral observations of the lower solar atmosphere (chromosphere and transition region) during coronal heating events, in combination with predictions from models of impulsively heated loops, provide powerful diagnostics of the ...
Paola Testa +3 more
doaj +1 more source
Chromospheric activity and rotation of FGK stars in the solar vicinity [PDF]
Astronomy and Astrophysics, 2010 Context: Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles and their perturbations alter the line centroids creating a radial ...
Martínez Arnáiz, R. +4 more
openaire +4 more sources
Magnetic Field Information in the Near-ultraviolet Fe ii Lines of the CLASP2 Space Experiment
The Astrophysical Journal, 2023 We investigate theoretically the circular polarization signals induced by the Zeeman effect in the Fe ii lines of the 279.3–280.7 nm spectral range of the CLASP2 space experiment and their suitability to infer solar magnetic fields. To this end, we use a
David Afonso Delgado +2 more
doaj +1 more source
A Survey of Chromospheric Activity in the Solar‐Type Stars in the Open Cluster M67 [PDF]
The Astrophysical Journal, 2006 We present the results of a spectroscopic survey of the Ca II H & K core strengths in a sample of 60 solar-type stars that are members of the solar-age and solar-metallicity open cluster M67. We adopt the HK index, defined as the summed H+K core strengths in 0.1 nm bandpasses centered on the H and K lines, respectively, as a measure of the ...
Giampapa, Mark S. +3 more
openaire +2 more sources
Structure of the Solar Atmosphere: A Radio Perspective
Frontiers in Astronomy and Space Sciences, 2020 Solar radio emission has been providing information about the Sun for over half a century. In order to fully exploit this information, one needs to have a broader view of the solar atmosphere, which cannot be provided by radio observations alone.
Costas E. Alissandrakis
doaj +1 more source
Observational signatures of waves and flows in the solar corona [PDF]
, 2015 DM acknowledges support of a Royal Society University Research Fellowship and a KU Leuven Research Council senior research fellowship (SF/12/008). The research leading to these results has also received funding from the European Commission Seventh ...
Antolin, Patrick +3 more
core +1 more source
The New Composite Solar Flare Index from Solar Cycle 17 to Cycle 24 (1937 – 2020)
, 2022 The chromosphere is a highly dynamic outer plasma layer of the Sun. Its physical processes accounting for the variability are poorly understood. We reconstructed the solar chromospheric flare index (SFI) to study the solar chromospheric variability from ...
Acosta Jara, Jose Nemesio
core +1 more source