Results 61 to 70 of about 860 (219)

Spatial and Temporal Analysis of Quiescent Coronal Rain over an Active Region

The Astrophysical Journal, 2023
The solar corona produces coronal rain, hundreds of times colder and denser material than the surroundings. Coronal rain is known to be deeply linked to coronal heating, but its origin, dynamics, and morphology are still not well understood.
Seray Şahin, Patrick Antolin, Clara Froment, Thomas A. Schad   +3 more
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

Turbulence and Its Potential Impact on Solar Chromospheric and Coronal Heating

The Astrophysical Journal
Low-frequency turbulence in the solar chromosphere remains poorly understood. We address (1) the sources of low-frequency turbulence that potentially heat the chromosphere, and (2) how turbulence is transported and dissipated throughout the chromosphere ...
G. P. Zank, Xiaocan Li, K. Khanal, Alphonse C. Sterling, M. Nakanotani, L.-L. Zhao, L. Adhikari, M. Yalim, P. S. Athiray, Fan Guo, R. L. Moore   +10 more
doaj   +1 more source

Photospheric and Chromospheric Magnetic Field Evolution during the X1.6 Flare in Active Region NOAA 12192

The Astrophysical Journal, 2023
We report on observations acquired by the Interferometric Bidimensional Spectropolarimeter (IBIS) during SOL2014-10-22T14:02, an X1.6 flare that occurred in active region NOAA 12192, taken in the Fe i 617.30 nm and Ca ii 854.2 nm line profiles.
F. Ferrente, F. Zuccarello, S. L. Guglielmino, S. Criscuoli, P. Romano   +4 more
doaj   +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

Magnetic Fields beneath Active Region Coronal Loops

The Astrophysical Journal
We examine the hypothesis that multipolar magnetic fields advected by photospheric granules can contribute to heating the active chromosphere and corona.
Philip G. Judge, L. Kleint, C. Kuckein
doaj   +1 more source

The evolution of chromospheric activity and the spin-down of solar-type stars

The Astrophysical Journal, 1985
IUE data for 31 solar-type stars are compared with observations of T Tauri stars in order to determine whether the pattern of main sequence chromospheric decay shown by stars older than about 100 million yr extends back to ages of 100 million yr appropriate for T Tauri stars.
T. Simon, A. M. Boesgaard, G. Herbig
openaire   +1 more source

IUE Observations of the Chromospheric Activity-Age Relation in Young Solar-Type Stars [PDF]

Symposium - International Astronomical Union, 1983
The difficulties of measuring magnetic fields in late-type stars other than the sun are well known, as one is reminded by other contributions to these Proceedings. This Symposium nevertheless comes at a very opportune time, as we are now at the point where we can begin to explore the relationship of stellar magnetism to flare activity and quiescent ...
Theodore Simon, Ann Merchant Boesgaard
openaire   +2 more sources

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

Solar activity monitoring and forecasting capabilities at Big Bear Solar Observatory [PDF]

Annales Geophysicae, 2002
The availability of full-disk, high-resolution Ha images from Big Bear Solar Observatory (USA), Kanzelhöhe Solar Observatory (Austria), and Yunnan Astronomical Observatory (China) allows for the continual monitoring of solar activity with ...
P. T. Gallagher, P. T. Gallagher, P. T. Gallagher, C. Denker, V. Yurchyshyn, T. Spirock, J. Qiu, H. Wang, P. R. Goode   +8 more
doaj   +1 more source