Results 61 to 70 of about 146,288 (166)

Ultraviolet observations of stellar chromospheric activity

The Astrophysical Journal, 1982
A survey is presented of chromospheric and transition region (TR) line emission in late-type stars obtained with the IUE satellite. A wide variation in TR emission (ions formed near T = 100,000 K) at a given position in the H-R diagram is found, contradicting theories that incorporate only acoustic energy generation and deposition.
L. Hartmann, A. K. Dupree, J. C. Raymond
openaire   +1 more source

The Influence of Stellar Chromospheres and Coronae on Exoplanet Transmission Spectroscopy

The Astrophysical Journal Letters
A main source of bias in transmission spectroscopy of exoplanet atmospheres is magnetic activity of the host star in the form of stellar spots, faculae, or flares. However, the fact that main-sequence stars have a chromosphere and a corona and that these
Volker Perdelwitz, Adam Chaikin-Lifshitz, Aviv Ofir, Oded Aharonson   +3 more
doaj   +1 more source

Comparison of Solar Imaging Feature Extraction Methods in the Context of Space Weather Prediction With Deep Learning‐Based Models

Journal of Geophysical Research: Machine Learning and Computation, Volume 2, Issue 3, September 2025.
Abstract Recently, many machine learning‐based models have been developed to predict geomagnetic activity several days in advance directly from space‐borne solar imaging. To better understand and improve these models, we compare dimensionality reduction techniques to extract abstract features from solar images for space weather‐related downstream tasks.
Maria Tahtouh, Guillerme Bernoux, Antoine Brunet, Denis Standarovski, Gautier Nguyen, Angélica Sicard   +5 more
wiley   +1 more source

Far-ultraviolet Emission Line Investigation of Flares on AU Mic

The Astrophysical Journal
The role of nonthermal proton energy transportation during solar and stellar flares is largely unknown; a better understanding of this physical process will allow us to rectify longstanding deficiencies in flare models.
Adalyn Gibson, Adam F. Kowalski, Adina D. Feinstein   +2 more
doaj   +1 more source

Deriving the Coronal Separatrix‐Web With the WSA Model

Journal of Geophysical Research: Space Physics, Volume 130, Issue 8, August 2025.
Abstract We demonstrate a new capability of the Wang‐Sheeley‐Arge (WSA) model to routinely derive the coronal separatrix web (S‐web) as a standard data product. We describe our methodology for deriving the squashing factor (Q $Q$) and we use Carrington rotation (CR) 2109 to illustrate the validation of our output with that derived from the POT3D model.
Samantha Wallace, Aleida K. Higginson, David G. Simpson, Nicholeen M. Viall, Peter Wyper, C. Nick Arge   +5 more
wiley   +1 more source

Wavelet Analysis of Stellar Chromospheric Activity Variations

The Astrophysical Journal, 1997
Observations of chromospheric activity variations for some lower main-sequence stars from the Mount Wilson Observatory's HK project reveal a cyclic behavior comparable to the sunspot cycle. Even in the relatively short interval that they have been observed, those stars show stellar cycles and other features, like grand minima. The quasi-periodic nature
P. Frick, S. L. Baliunas, D. Galyagin, D. Sokoloff, W. Soon   +4 more
openaire   +1 more source

Solar Wind Heavy Ions and Alpha Particles Within Earth's Magnetosphere and Their Variability With Upstream Conditions

Journal of Geophysical Research: Space Physics, Volume 130, Issue 8, August 2025.
Abstract Working toward the goal of understanding solar wind (SW) entry to the Earth's magnetosphere, this study examines solar‐origin ion composition in the magnetotail. During its trajectory, Wind spent a significant amount of time in the Earth's magnetotail, where its SupraThermal Ion Composition Spectrometer (STICS) measured the mass and mass per ...
S. Colón‐Rodríguez, M. W. Liemohn, J. M. Raines, S. T. Lepri   +3 more
wiley   +1 more source

Evidence for extended chromospheres surrounding red giant stars [PDF]

, 1982
Observational evidence and theoretical arguments are summarized which indicate that regions of partially ionized hydrogen extending several stellar radii are an important feature of red giant and supergiant stars.
Stencel, R. E.
core  

Double-edged Sword: The Influence of Tidal Interaction on Stellar Activity in Binaries

The Astrophysical Journal
Using the LAMOST DR7 low-resolution spectra, we carried out a systematic study of stellar chromospheric activity in both single and binary stars. We constructed a binary sample and a single-star sample, mainly using the binary belt and the main sequence ...
Yuedan Ding, Shidi Zhang, Henggeng Han, Wenyuan Cui, Song Wang, Min Fang, Yawei Gao   +6 more
doaj   +1 more source

Slow Solar Wind: Origin in an Independent Small‐Scale Solar Dynamo

Geophysical Research Letters, Volume 52, Issue 13, 16 July 2025.
Abstract Separation of the solar wind (SW) into three flow types (coronal mass ejections (CMEs), high speed streams (HSSs), and slow solar wind (SSW)) reveals an inverse relationship between the percentage of time Earth spends in SSW during a year and its annually averaged magnetic field strength (B).
E. W. Cliver, I. G. Richardson, S. F. Martin   +2 more
wiley   +1 more source