Results 21 to 30 of about 318 (133)

ALMA Detection of Dark Chromospheric Holes in the Quiet Sun [PDF]

The Astrophysical Journal Letters, 2019
Abstract We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of a quiet-Sun region at a wavelength of 3 mm, obtained during the first solar ALMA cycle on 2017 April 27, and compare them with available chromospheric observations in the UV and visible as well as with photospheric magnetograms.
Maria A. Loukitcheva, Stephen M. White, Sami K. Solanki   +2 more
openaire   +3 more sources

Basal chromospheric flux and Maunder Minimum-type stars: the quiet-Sun chromosphere as a universal phenomenon [PDF]

Astronomy & Astrophysics, 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. Methods: We discuss measurements of the solar Mt.
Schroeder, K. -P., Mittag, M., Martinez, M. I. Perez, Cuntz, M., Schmitt, J. H. M. M.   +4 more
openaire   +2 more sources

Processes in the magnetized chromosphere of the Sun [PDF]

Proceedings of the International Astronomical Union, 2008
AbstractWe review physical processes in magnetized chromospheres on the Sun. In the quiet chromosphere, it is useful to distinguish between the magnetic network on the boundaries of supergranules, where strong magnetic fields are organized in mainly vertical flux tubes and internetwork regions in the cell interiors, which have traditionally been ...
openaire   +1 more source

On the Magnetic Nature of Quiet-Sun Chromospheric Grains

The Astrophysical Journal Letters, 2023
Abstract Ca ii K grains, i.e., intermittent, short-lived (about 1 minute), periodic (2–4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere.
María Jesús Martínez González, Tanausú del Pino Alemán, Adur Pastor Yabar, C. Quintero Noda, Andrés Asensio Ramos   +4 more
openaire   +2 more sources

The quiet sun chromospheric network observed from SKYLAB

The Astrophysical Journal, 1976
The paper analyzes spectra of a supergranulation cell interior and cell boundary obtained near the solar center at wavelengths between 1200 and 1560 A with a normal-incidence spectrograph aboard Skylab. Absolute intensities, relative intensities, and profiles are given for selected optically thin and optically thick lines over the cell interior, the ...
U. Feldman, G. A. Doschek, N. P. Patterson   +2 more
openaire   +1 more source

Parker Solar Probe Observations of Proton Core‐Beam Distributions in Heliospheric Current Sheet Region: Quasilinear Instability Analysis Combined With Collisional Relaxation

Journal of Geophysical Research: Space Physics, Volume 131, Issue 4, April 2026.
Abstract Parker Solar Probe has been proven as instrumental for the observation of young solar wind. During the encounters E‐07 and E‐08, PSP recorded the core plus beaming protons crossing the heliospheric current Sheet region. When the observed PSP data is plotted in the temperature ratio versus parallel beta space, it is found that the occurrence ...
M. Rashid, P. H. Yoon, J. Huang, C. Salem, M. Sarfraz, S. Alnussirat, R. A. López, J. Seough, H. Xie, D. Larson, R. Livi   +10 more
wiley   +1 more source

Reconstruction of Two‐Dimensional Magnetohydrodynamic and Hall Magnetohydrodynamic Equilibria in Space Using Physics‐Informed Neural Networks

Journal of Geophysical Research: Machine Learning and Computation, Volume 3, Issue 2, April 2026.
Abstract We present a novel data analysis technique based on physics‐informed neural networks (PINNs) to reconstruct two‐dimensional (2D) magnetohydrodynamic (MHD) and Hall MHD equilibria in a space plasma from in situ spacecraft measurements. Our method incorporates the steady‐state MHD or Hall MHD equations—a set of partial differential equations ...
Hiroshi Hasegawa, Eunjin Choi, Kyoung‐Joo Hwang, Kyunghwan Dokgo   +3 more
wiley   +1 more source

Reconstructing Historical Solar Indices for Predicting Past Space Weather Events

Space Weather, Volume 24, Issue 4, April 2026.
Abstract Modeling and forecasting the near‐Earth space environment, specifically the thermosphere, is particularly important because it affects the motion of low‐Earth orbit objects through atmospheric drag. Solar indices such as F10.7, S10.7, M10.7, and Y10.7 are commonly used as inputs to ionospheric and thermospheric density models.
Poshan Belbase, Denny M. Oliveira, Theodosios Chatzistergos, Gangkai Poh, Eftyhia Zesta   +4 more
wiley   +1 more source

What is heating the quiet-Sun chromosphere?

, 2006
10 pages, 3 figures, to appear in the proceedings of the Coimbra Solar Physics Meeting on The Physics of Chromospheric Plasmas, 2006, eds. P. Heinzel, I. Dorotovic, and R.
Wedemeyer-Böhm, S., Steiner, O., Bruls, J., Rammacher, W.   +3 more
openaire   +2 more sources

Searching for Rotational X‐Ray Modulation on TIC 277539431

Astronomische Nachrichten, Volume 347, Issue 3, March 2026.
ABSTRACT TIC 277539431, a fast rotating M7 dwarf, was detected to host the highest latitude flare to date at 81°$$ {81}^{{}^{\circ}} $$. Magnetic activity like stellar flares occurring at high latitude indicate occurrence of coronal loops at these latitudes on fully‐convective M dwarfs. In contrast, sunspots usually occur below 30°$$ {30}^{{}^{\circ}} $
Desmond Dsouza, Katja Poppenhäger, Ekaterina Ilin   +2 more
wiley   +1 more source