Results 21 to 30 of about 682 (184)

Chromospheric Prolateness: Solar Cycle Variations [PDF]

Proceedings of the International Astronomical Union, 2006
The solar prolateness (also known as Ovalisation, a french origin name) of the extended dynamical chromosphere is established from measurements performed above 2 Mm heights during the years of solar minimum, using the H$\alpha$, Ca II K and HeII 304 line emissions from both ground-based and space-based observations.
J. Vilinga, S. Koutchmy, Fr. Auchere, Fr. Baudin, B. Filippov, J-C. Noens   +5 more
openaire   +1 more source

Extreme Red-wing Enhancements of UV Lines during the 2022 March 30 X1.3 Solar Flare

The Astrophysical Journal, 2023
Here, we present the study of a compact emission source during an X1.3 flare on 2022 March 30. Within a ∼41 s period (17:34:48 UT to 17:35:29 UT), Interface Region Imaging Spectrograph observations show spectral lines of Mg ii , C ii , and Si iv with ...
Yan Xu, Graham S. Kerr, Vanessa Polito, Nengyi Huang, Ju Jing, Haimin Wang   +5 more
doaj   +1 more source

Magnetoacoustic Heating of the Solar Chromosphere

The Astrophysical Journal, 1991
Long-period acoustic waves generated in the solar convection zone can propagate radially outward through the overlying atmosphere and get resonantly absorbed in the magnetic arches of the low-lying chromospheric canopy. The resulting Poynting and acoustic flux that enters the magnetic canopy in the network regions is demonstrated to be adequate to ...
Joseph M. Davila, S. M. Chitre
openaire   +1 more source

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

Formation of the Lyman Continuum during Solar Flares

The Astrophysical Journal, 2023
The Lyman continuum (LyC;
Shaun A. McLaughlin, Ryan O. Milligan, Graham S. Kerr, Aaron J. Monson, Paulo J. A. Simões, Mihalis Mathioudakis   +5 more
doaj   +1 more source

Resonance Lines in the Solar Chromosphere [PDF]

Symposium - International Astronomical Union, 1970
Stigmatic balloon spectra of the Sun in the vicinity of 2800 Å were obtained on September 22, 1968 and April 30, 1969. We compare the observed profiles of the H and K lines of ionized magnesium with the computed profiles of Athay and Skumanich and of Dumont. The discrepancy between observed and computed profiles of the Mgii lines is considerable. It is
openaire   +1 more source

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

Detection of a Magnetic Discontinuity in the Upper Solar Chromosphere Associated with a Coronal Loop Brightening Observed by CLASP2.1

The Astrophysical Journal
We report the first detection of a magnetic discontinuity in the upper solar chromosphere associated with a coronal loop brightening. Our findings are based on novel observations obtained by the Chromospheric LAyer SpectroPolarimeter (CLASP2.1 ...
Donguk Song, Ryohko Ishikawa, David E. McKenzie, Javier Trujillo Bueno, Frédéric Auchère, Ryouhei Kano, Amy Winebarger, Takenori J. Okamoto, Laurel A. Rachmeler, Ken Kobayashi, Genevieve D. Vigil, Adam R. Kobelski, Christian Bethge, Eun-Kyung Lim, Luca Belluzzi, Ernest Alsina Ballester, Tanausú del Pino Alemán, Jiří Štěpán   +17 more
doaj   +1 more source

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

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