Results 21 to 30 of about 1,774 (127)

Periodic Density Structures Observed in Ulysses Data: First Results

Journal of Geophysical Research: Space Physics, Volume 131, Issue 3, March 2026.
Abstract Periodic density structures (PDSs) are advecting quasi‐periodic (periodicities between several minutes and several hours) density enhancements observed in the solar wind and corona. There is strong evidence that PDSs are formed at the Sun.
Brent M. Randol, Nicholeen Viall, Larry Kepko, Simone Di Matteo   +3 more
wiley   +1 more source

Chromosphere of K giant stars Geometrical extent and spatial structure detection

, 2011
We aim to constrain the geometrical extent of the chromosphere of non-binary K giant stars and detect any spatial structures in the chromosphere. We performed observations with the CHARA interferometer and the VEGA beam combiner at optical wavelengths ...
A. Spang, Andretta, Ayres, B. Pichon, Baines, Berio, Bonneau, Brown, Busà, C. Farrington, Carpenter, Chen, Claret, Cuntz, Cuntz, D. Bonneau, D. Mourard, di Benedetto, Diaz-Cordoves, Dyck, Eaton, Eriksson, F. Thévenin, Gustafsson, H. McAlister, Hall, Houdashelt, I. Tallon-Bosc, J. M. Clausse, J. Sturmann, Judge, K. Perraut, Kovacs, L. Sturmann, Linsky, Luck, Massarotti, McWilliam, Meilland, Montes, Morel, Mourard, Mozurkewich, N. Nardetto, N. Turner, O. Chesneau, O. Delaa, P. Berio, P. J. Goldfinger, P. Stee, Perryman, Pietrinferni, R. Ligi, Reimers, Richichi, Simon, Skrutskie, T. Merle, T. ten Brummelaar, ten Brummelaar, van Belle, van Leeuwen, White   +62 more
core   +3 more sources

On the Freeze‐In Distance of Solar Wind Fluid Entropy Variability in the Corona

Journal of Geophysical Research: Space Physics, Volume 131, Issue 3, March 2026.
Abstract The strong correlation between solar wind entropy and the frozen‐in ion charge state ratio O7+/O6+ ${\mathrm{O}}^{7+}/{\mathrm{O}}^{6+}$ indicates that entropy variability on timescales of hours or longer is preserved from its solar source. This prompts the question: where in the solar atmosphere does this entropy variability come from, and at
Aidan J. Nakhleh, Nicholeen M. Viall, Susan T. Lepri, Jim M. Raines   +3 more
wiley   +1 more source

Basal Chromospheric Flux and Maunder Minimum-type Stars: The quiet-Sun Chromosphere as a Universal Phenomenon

, 2012
Aims: We demonstrate the universal character of the quiet-Sun chromosphere among inactive stars (solar-type and giants). By assessing the main physical processes, we shed new light on some common observational phenomena.
Baliunas, Brandenburg, Buchholz, Cuntz, Cuntz, Duncan, Hall, Hauschildt, J. H. M. M. Schmitt, Judge, Judge, Judge, Judge, K.-P. Schröder, Keppens, Konstantinova-Antova, M. Cuntz, M. I. Pérez Martínez, M. Mittag, Mittag, Pasquini, Pevtsov, Pérez Martínez, Rammacher, Riethmüller, Schmitt, Schrijver, Schrijver, Schrijver, Schrijver, Schröder, Schröder, Schröder, Schwarzschild, Strassmeier, Stȩpień, Suzuki, Vögler, White, Wöger   +39 more
core   +1 more source

Stellar chromospheres and coronae

The Astrophysical Journal, 1981
The basic structural features of the solar chromosphere and corona are identified either with physical properties of the plasma or with properties of the energy input. It is argued that those properties identified with plasma physics should be relatively invariant whereas those identified with the energy input should vary from star to star.
openaire   +1 more source

Solar Activity Impacts on Ionospheric Scintillation and Precise Point Positioning Based on Multi‐Year GNSS and Scintillation Observations

Space Weather, Volume 24, Issue 3, March 2026.
Abstract Solar activity induces ionospheric irregularities that degrade Global Navigation Satellite System (GNSS) performance through amplitude and phase scintillation. Although numerous studies have investigated event‐driven or regional responses, the nonlinear coupling between solar radiation, ionospheric scintillation, and precise point positioning (
Jincheng Li, Qi Liu, Xiaomin Luo, Manuel Hernández‐Pajares, Enric Monte‐Moreno, Guangxia Wang, Heng Yang, Chuanding Zhang, Li Yang, Yaoyao Liu   +9 more
wiley   +1 more source

Accretion-powered chromospheres in classical T Tauri stars [PDF]

, 2011
(Abridged) Optical spectra of classical T Tauri stars (cTTS) are rich in emission lines of low-excitation species that are composed of narrow and broad components, related to two regions with different kinematics, densities, and temperatures.
Aiad, Al-Naimi, Alencar, Appenzeller, Ardila, Argiroffi, Artemenko, Basri, Batalha, Berdyugina, Beristain, Beristain, Bertout, Bertout, Bertout, Bertout, Bouvier, Bouvier, Brickhouse, Calvet, Chavarria-K., Cram, Cram, Dall, Donati, Donati, Donati, Donati, Edwards, Edwards, F. M. Walter, Fang, Fischer, G. F. Gahm, Gahm, Gameiro, Grankin, Guenther, Gullbring, Gullbring, Güdel, H. C. Stempels, Hartigan, Hartigan, Hessman, Hussain, Johns, Johns-Krull, Kenyon, Krautter, Kravtsova, Kupka, Kwan, Lamzin, Lamzin, Long, Lorenzetti, Mohanty, Mundt, Muzerolle, Muzerolle, Orlando, P. P. Petrov, Percy, Petrov, Petrov, Petrov, Richter, Romanova, Romanova, Romanova, S. A. Artemenko, Smith, Smith, Stempels, Stempels, Valenti, Van Den Ancker   +77 more
core   +1 more source

Stellar model chromospheres. XIII - M dwarf stars

The Astrophysical Journal, 1982
Single-component, homogeneous model chromospheres that are consistent with high-resolution profiles of the Ca II K line calibrated in surface flux units for three dMe and 2 dM stars observed at quiescent times are constructed. The models reveal several systematic trends.
M. S. Giampapa, S. P. Worden, J. L. Linsky   +2 more
openaire   +1 more source

A New Method for Probabilistic Spatiotemporal Forecasts of Solar Soft X‐Ray “S‐Class” (>X10) Superflares

Journal of Geophysical Research: Space Physics, Volume 131, Issue 2, February 2026.
Abstract Solar superflares of S‐class (>X10 in soft X‐rays) pose extreme space weather hazards, yet their prediction remains a fundamental challenge owing to their rapid and transient natures and the limitations of conventional event‐based forecasts. We introduce for the first time, a probabilistic spatiotemporal framework designed to identify extended
V. M. Velasco Herrera, G. Velasco Herrera, W. Soon, A. Özgüç, N. Babynets, A. Tlatov, M. Švanda, S. Qiu, S. Baliunas, B. Kotan, G. González González, L. A. Bautista Flores, M. Pazos   +12 more
wiley   +1 more source

Space Weather Impact of Three Solar Flares Observed by the POEMAS Telescope at 45 and 90 GHz

Journal of Geophysical Research: Space Physics, Volume 130, Issue 11, November 2025.
Abstract Solar flares are often associated with coronal mass ejections (CMEs) that, when directed toward Earth, can disrupt the magnetosphere and impact space weather. In this study, we investigate three long‐duration solar flares observed in 2012 by the POlarization Emission of Millimeter Activity at the Sun (POEMAS) telescopes at 45 and 90 GHz.
Adriana Valio, Karla F. Lopez, José Luis Gamonal Valenzuela, Ruben M. Romero Ramírez, Dougas F. da Silva   +4 more
wiley   +1 more source