Results 71 to 80 of about 146,288 (166)

The Stagger Code for Accurate and Efficient, Radiation-coupled Magnetohydrodynamic Simulations

The Astrophysical Journal
We describe the Stagger code for simulations of magnetohydrodynamic (MHD) systems. This is a modular code with a variety of physics modules that will let the user run simulations of deep stellar atmospheres, sunspot formation, stellar chromospheres and ...
Robert F. Stein, Åke Nordlund, Remo Collet, Regner Trampedach   +3 more
doaj   +1 more source

Robust Statistical Techniques for Operational Maintenance of the 10.7 cm Solar Radio Flux

Space Weather, Volume 23, Issue 5, May 2025.
Abstract The F10.7 solar radio flux is a critical quantity for operational space weather nowcasting and forecasting, where it is routinely used as a driver for coupled atmospheric models to estimate a variety of important quantities such as the neutral atmospheric density.
Daniel A. Brandt, Erick F. Vega, Brian J. Thelen   +2 more
wiley   +1 more source

Quasi‐Periodic Pulsations in Ionospheric TEC Synchronized With Solar Flare EUV Emission

Journal of Geophysical Research: Space Physics, Volume 130, Issue 4, April 2025.
Abstract The extreme ultraviolet (EUV) and X‐ray radiation emitted during solar flares has been shown to significantly increase the electron density of the Earth's ionosphere. During flares, quasi‐periodic pulsations in X‐ray flux originating in the corona have previously been linked to subsequent pulsations in the Earth's ionospheric D‐region. Similar
Aisling N. O’Hare, Susanna Bekker, Laura A. Hayes, Ryan O. Milligan   +3 more
wiley   +1 more source

Stellar Chromospheric Activity Database of Solar-like Stars Based on the LAMOST Low-resolution Spectroscopic Survey. III. Calibrating the Chromospheric Basal Flux and the Connection to Stellar Rotation

The Astrophysical Journal Supplement Series
Based on the Ca ii H and K lines observed by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, we employ the photospheric ( ${R}_{{\rm{HK}}}^{{\prime} }$ ) and basal ( ${R}_{{\rm{HK}},L}^{+}$ ) flux-calibrated chromospheric activity indices ...
Weitao Zhang, Han He, Jun Zhang
doaj   +1 more source

Evidence for stellar chromospheres presented by ultraviolet observations of the sun and stars [PDF]

, 1973
Observations of emission lines in stellar sources in the ultraviolet region of the spectrum show P Cygni-like evidence of mass outflow as well as many ultraviolet emission lines which cannot be interpreted wholly in terms of geometric effects.
Doherty, L.
core  

Investigating the Temperature Sensitivity of UV Line Ratios in the 280 nm Region of Solar-like Stars

The Astrophysical Journal
Stellar UV spectra are fundamental diagnostics of physical and magnetic properties of stars. For instance, lines like Mg ii at 280 nm serve as valuable indicators of stellar activity, providing insights into the activity levels of Sun-like stars and ...
Valentina Penza, Serena Criscuoli, Raffaele Reda, Luca Bertello, Giuseppe Bono, Dario Del Moro, Valentina D’Orazi, Luca Giovannelli, Giuseppina Nigro, Francesco Berrilli   +9 more
doaj   +1 more source

On the Origin and Evolution of Stellar Chromospheres, Coronae and Winds [PDF]

, 1997
The final report discusses work completed on proposals to construct state-of-the-art, theoretical, two-component, chromospheric models for single stars of different spectral types and different evolutionary status.
Musielak, Z. E.
core  

The Strength and Variability of the Helium 10830 Å Triplet in Young Stars, with Implications for Exosphere Detection

The Astronomical Journal
Young exoplanets trace planetary evolution, in particular the atmospheric mass loss that is most dynamic in youth. However, the high activity level of young stars can mask or mimic the spectroscopic signals of atmospheric mass loss.
Daniel M. Krolikowski, Adam L. Kraus, Benjamin M. Tofflemire, Caroline V. Morley, Andrew W. Mann, Andrew Vanderburg   +5 more
doaj   +1 more source

Final report on the STELLAR Delphi study: Future directions for TEL and TEL research: areas of tension, core research areas and grand challenge problems

, 2012
In this report on the STELLAR Delphi study, we present the results of the final global survey, that is the 4th STELLAR Delphi round, and illustrate the elaboration and dissemination of these results (5th STELLAR Delphi round).
Spada, Hans, Plesch, Christine, Wiedmann, Michael   +2 more
core   +2 more sources

Intermediate report on the Delphi study: Findings from the 2nd and the 3rd STELLAR Delphi rounds: Areas of tension and core research areas

, 2011
This intermediate report on the STELLAR Delphi study closes the gap between the first deliverable on the Delphi study D1.3 (Spada et al. 2010) which was published in July 2010 and the second and final deliverable D1.6 which is planned for January 2012 ...
Spada, Hans, Plesch, Christine, Kaendler, Celia   +2 more
core   +2 more sources