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Transverse magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere and may be responsible for generating the Sun's million-degree outer atmosphere. However, direct evidence of the dissipation process and heating from these…

Solar and Stellar Astrophysics · Physics 2015-08-19 Patrick Antolin , Takenori J. Okamoto , Bart De Pontieu , Han Uitenbroek , Tom Van Doorsselaere , Takaaki Yokoyama

The Sun is an extraordinary workbench, from which several fundamental astronomical parameters can be measured with high precision. Among these parameters, the solar radius $R_{\odot}$ plays an important role in several aspects, such as in…

Context. The radiative losses in the solar chromosphere vary from 4~kW~m$^{-2}$ in the quiet Sun, to 20~kW~m$^{-2}$ in active regions. The mechanisms that transport non-thermal energy to and deposit it in the chromosphere are still not…

Solar and Stellar Astrophysics · Physics 2018-04-18 Jorrit Leenaarts , Jaime de la Cruz Rodríguez , Sanja Danilovic , Göran Scharmer , Mats Carlsson

Low-frequency radio observations of diffuse synchrotron radiation offer a unique vantage point for investigating the intricate relationship between gas and magnetic fields in the formation of structures within the Galaxy, spanning from the…

Astrophysics of Galaxies · Physics 2024-05-29 Andrea Bracco , Marco Padovani , Daniele Galli

We test our knowledge of the atomic opacity in the solar UV spectrum. Using the atomic data compiled in Paper I from modern, publicly available, databases, we perform calculations that are confronted with space-based observations of the…

Astrophysics · Physics 2009-11-07 C. Allende Prieto , I. Hubeny , D. L. Lambert

The dynamical evolution and radiative properties of luminous radio galaxies and quasars of the FRII type, are well understood. As a result, through the use of detailed modeling of the observed radio emission of such sources, one can…

Astrophysics of Galaxies · Physics 2021-12-08 Anna Wojtowicz , Lukasz Stawarz , Jerzy Machalski , Luisa Ostorero

Supra-arcade downflows (SADs) are infrequent, wiggly opaque structures observed to descend through the solar corona, mostly in EUV and soft X-ray frequencies. From their physical characteristics, SADs have been interpreted as voided…

Solar and Stellar Astrophysics · Physics 2022-03-04 Ernesto Zurbriggen , C. Guillermo Giménez de Castro , Andrea Costa , Mariana Cécere , Caius L. Selhorst

We search for signatures of high-frequency oscillations in the upper solar photosphere and low chromosphere in the context of acoustic heating of outer stellar atmospheres. We use ultraviolet image sequences of a quiet center-disk area from…

Astrophysics · Physics 2009-06-23 A. G. de Wijn , R. J. Rutten , T. D. Tarbell

The total solar fluxes at 1, 2, 3.75, and 9.4 GHz were observed continuously from 1957 to 1994 at Toyokawa, and from 1994 until now at Nobeyama, Japan with the current Nobeyama Radio Polarimeters. We examined the multi-frequency and…

Solar and Stellar Astrophysics · Physics 2017-10-18 M. Shimojo , K. Iwai , A. Asai , S. Nozawa , T. Minamidani , M. Saito

We use high spatial and temporal resolution observations, simultaneously obtained with the New Vacuum Solar Telescope and Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, to investigate the high-frequency…

Solar and Stellar Astrophysics · Physics 2018-03-28 Feng Wang , Hui Deng , Bo Li , Song Feng , Xianyong Bai , Linhua Deng , Yunfei Yang , Zhike Xue , Rui Wang

Waves are thought to play a significant role in the heating of the solar atmosphere and the acceleration of the wind. Among the many types of waves observed in the Sun, the so-called p-modes with a 3 mHz frequency peak dominate the lower…

The solar F10.7 index is has been a reliable and sensitive activity index since 1947. As with other indices, it has been showing unusual behavior in the Cycle 23/24 minimum. The origins of the solar microwave flux lie in a variety of…

Solar and Stellar Astrophysics · Physics 2010-03-24 Leif Svalgaard , Hugh S. Hudson

We statistically study the property of emerging flux regions (EFRs) and the upper solar atmosphere response to the flux emergence by using data from the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) on…

Solar and Stellar Astrophysics · Physics 2015-06-05 Jie Zhao , Hui Li

Reconstructions of solar spectral irradiance - especially in the ultraviolet (UV) range - are crucial for understanding Earth's climate system. Although total solar irradiance (TSI) has been thoroughly investigated, the spectral composition…

Present-day semi-empirical models of solar irradiance (SI) variations employ spectra computed on one-dimensional atmosphere models (1D models) representative of various solar surface features to reconstruct SI changes measured on timescales…

Solar and Stellar Astrophysics · Physics 2017-06-14 A. Cristaldi , I. Ermolli

Remarkable progress has been made in understanding turbulent astrophysical plasmas in past decades including, notably, the solar wind and the interstellar medium. In the case of the solar wind, much of this progress has relied on in situ…

Solar and Stellar Astrophysics · Physics 2019-04-12 Tim Bastian , James Cordes , Justin Kasper , Adam Kobelski , Kelly Korreck , Gregory Howe , Steven Spangler , Chadi Salem , Angelos Vourlidas

The suitability of solar pores as magnetic wave guides has been a key topic of discussion in recent years. Here we present observational evidence of propagating magnetohydrodynamic wave activity in a group of five photospheric solar pores.…

We model the deepest observable layers of dark sunspot umbral atmospheres in terms of an empirical model which equally describes observed near infrared continuum intensities and line profiles. We use the umbral continuum intensity at 1.67…

Solar and Stellar Astrophysics · Physics 2012-10-17 Goetz Stellmacher , Eberhard Wiehr

Extreme-ultraviolet images from the Solar Dynamics Observatory often show looplike fine structure to be present where no minority-polarity flux is visible in magnetograms, suggesting that the rate of ephemeral region (ER) emergence inside…

Solar and Stellar Astrophysics · Physics 2021-04-14 Y. -M. Wang

We have carried out numerical simulation based on the equations of radiation magnetohydrodynamics to study the interaction of solar granules and small-scale magnetic fields in photospheric regions with various magnetic fluxes. Four…

Solar and Stellar Astrophysics · Physics 2010-11-09 I. N. Atroshchenko , V. A. Sheminova
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