Results 71 to 80 of about 14,496 (257)

Observing the Solar Chromosphere

, 2007
This review is split into two parts: one on chromospheric line formation in answer to the frequent question "where is my line formed", and one presenting state-of-the-art imagery of the chromosphere. In the first part I specifically treat the formation of the Na D lines, Ca II H & K, and Halpha.
openaire   +4 more sources

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

Calcium Bright Knots and the Formation of Chromospheric Anemone Jets on the Sun

The Astrophysical Journal Letters
Space-based observations show that the solar atmosphere from the solar chromosphere to the solar corona is filled with small-scale jets and is linked with small-scale explosions.
Kunwar Alkendra Pratap Singh, Keisuke Nishida, Kazunari Shibata   +2 more
doaj   +1 more source

On the origin of the magnetic energy in the quiet solar chromosphere

, 2019
The presence of magnetic field is crucial in the transport of energy through the solar atmosphere. Recent ground-based and space-borne observations of the quiet Sun have revealed that magnetic field accumulates at photospheric heights, via a local dynamo
Carlsson, Mats, De Pontieu, Bart, Gosic, Milan, Gudiksen, Boris, Hansteen, Viggo H., Martínez-Sykora, Juan   +5 more
core   +1 more source

Solar mean magnetic field of the chromosphere

Journal of Astrophysics and Astronomy, 2023
The Solar Mean Magnetic Field (SMMF) is the mean value of the line of sight (LOS) component of the solar vector magnetic field averaged over the visible hemisphere of the Sun. So far, the studies on SMMF have mostly been confined to the magnetic field measurements at the photosphere. In this study, we calculate and analyse the SMMF using magnetic field
M. Vishnu, K. Nagaraju, Harsh Mathur
openaire   +2 more sources

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

The magnetic sensitivity of the Ca II H and K lines

Astronomy & Astrophysics
Context. The solar chromosphere is a transition layer between the cool, dense photosphere and the hot, rarefied corona. This boundary region plays a key role in regulating energy transport and structuring the magnetic field throughout the solar ...
Kriginsky M., Leenaarts J., de la Cruz Rodríguez J., Danilovic S., Andriienko O.   +4 more
doaj   +1 more source

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

, 2010
We study horizontal supergranule-scale motions revealed by TRACE observation of the chromospheric emission, and investigate the coupling between the chromosphere and the underlying photosphere.
Aiouaz, Aiouaz, Attie, Axford, Berrilli, Cadavid, Carlsson, Chae, Curdt, Dammasch, Damé, Damé, de Wijn, de Wijn, Deubner, Dowdy, E. Marsch, Foukal, Gabriel, Giovanelli, Goode, Goode, H. E. Potts, H. Tian, Handy, He, He, Hoekzema, Hoekzema, Hoekzema, Innes, J.-S. He, Jin, Kamio, Krijger, Krijger, Leighton, Lin, Lites, Livingston, Loukitcheva, Marsch, Marsch, Martin, McAteer, McIntosh, Nindos, November, November, November, November, Peter, Potts, Potts, Potts, R. Attie, Rast, Remling, Rieutord, Rimmele, Roudier, Rutten, Rutten, Rutten, Rutten, Shimojo, Simon, Simon, Sivaraman, Sivaraman, Skartlien, Solanki, Strous, Tian, Tian, Tian, Tian, Title, Tritschler, Tu, Vernazza, Wang, Wang, Wang, Wang, Wedemeyer, Worden, Yang, Yang, Yi, Zhang, Zhang, Zhang   +92 more
core   +1 more source

Solar Flare Activity, 1937–2024: Introducing the New Hemispheric Solar Flare Index (hSFI) in the Context of 2024's Major Solar Storm Events

Space Weather, Volume 23, Issue 11, November 2025.
Abstract A new daily composite of the solar flare index (SFI) and the hemispherically‐resolved versions (hSFI) are presented for 1937 to 2024. The data set confirms that the northern hemisphere (NH) dominated solar flare activity during Solar Cycles 17 to 21, but that the southern hemisphere has dominated from Solar Cycle 22 to present.
V. M. Velasco Herrera, W. Soon, S. Knoška, A. Özgüç, G. Velasco Herrera, H. Yeşilyaprak, N. Babynets, M. Švanda, J. Muraközy, S. Qiu, D. Riveros‐Rosas, R. Connolly, M. Connolly, A. Tlatov, L. Cappellotto   +14 more
wiley   +1 more source

Measurement of Turbulence Injection Scale Down to the Chromosphere

The Astrophysical Journal Letters
The solar atmosphere displays a sharp temperature gradient, starting from spicules in the chromosphere at 2 × 10 ^4 K, outward into the corona exceeding ${10}^{6}$ K.
Zachary Bailey, Riddhi Bandyopadhyay, Shadia Habbal, Miloslav Druckmüller   +3 more
doaj   +1 more source