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We study the influence of the spatial resolution on scales of $5\deg$ and smaller of solar surface magnetic field maps on global magnetohydrodynamic solar wind models, and on a model of coronal heating and X-ray emission. We compare the…

Solar and Stellar Astrophysics · Physics 2013-05-13 C. Garraffo , O. Cohen , J. J. Drake , C. Downs

Sun-as-a-star coronal plasma composition, derived from full-Sun spectra, and the F10.7 radio flux (2.8 GHz) have been shown to be highly correlated (r = 0.88) during solar cycle 24. However, this correlation becomes nonlinear during…

It is widely accepted that X-ray emission in luminous active galactic nuclei (AGNs) originates from hot corona. To prevent the corona from over-cooling by strong X-ray emission, steady heating to the corona is essential, for which the most…

High Energy Astrophysical Phenomena · Physics 2023-11-27 Jie-Ying Liu , Jirong Mao , B. F. Liu

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also…

Solar and Stellar Astrophysics · Physics 2015-06-23 Thomas Wiegelmann , Julia K. Thalmann , Sami K. Solanki

The recent analysis of observations taken with the EIS instrument on Hinode suggests that well constrained measurements of the temperature distribution in solar active regions can finally be made. Such measurements are critical for…

Solar and Stellar Astrophysics · Physics 2015-06-04 Harry P. Warren , Amy R. Winebarger , David H. Brooks

This review discusses the complementary relationship between radio and hard X-ray observations of the Sun using primarily results from the era of the Reuven Ramaty High Energy Solar Spectroscopic Imager satellite. A primary focus of joint…

The characteristic electron densities, temperatures, and thermal distributions of 1MK active region loops are now fairly well established, but their coronal magnetic field strengths remain undetermined. Here we present measurements from a…

Solar and Stellar Astrophysics · Physics 2021-07-14 David H. Brooks , Harry P. Warren , Enrico Landi

How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the…

We present a correlation between X-ray surface brightness and Faraday rotation measure in galaxy clusters, both, from radio and X-ray observations as well as from modeling of the intra-cluster medium. The observed correlation rules out a…

Astrophysics · Physics 2009-11-07 K. Dolag , S. Schindler , F. Govoni , L. Feretti

The cause of excess spectral line broadening (non-thermal velocity) is not definitively known, but given its rise before and during flaring, the causal processes hold clues to understanding the triggers for the onset of reconnection and the…

Solar and Stellar Astrophysics · Physics 2024-01-23 James McKevitt , Robert Jarolim , Sarah Matthews , Deborah Baker , Manuela Temmer , Astrid Veronig , Hamish Reid , Lucie Green

The solar corona is full of dynamic phenomena, e.g., solar flares, micro flares in active regions, jets in coronal holes and in the polar regions, X-ray bright points in quiet regions, etc. They are accompanied by interesting physical…

Solar and Stellar Astrophysics · Physics 2017-06-15 Noriyuki Narukage , Shin-nosuke Ishikawa , Tomoko Kawate , Shinsuke Imada , Taro Sakao

Recent dedicated Hinode polar region campaigns revealed the presence of concentrated kilogauss patches of magnetic field in the polar regions of the Sun which are also shown to be correlated with facular bright points at the photospheric…

Solar and Stellar Astrophysics · Physics 2019-04-17 Nancy Narang , Dipankar Banerjee , Kalugodu Chandrashekhar , Vaibhav Pant

In the quiet solar photosphere, the mixed polarity fields form a magnetic carpet, which continuously evolves due to dynamical interaction between the convective motions and magnetic field. This interplay is a viable source to heat the solar…

Solar and Stellar Astrophysics · Physics 2014-09-16 L. P. Chitta , R. Kariyappa , A. A. van Ballegooijen , E. E. DeLuca , S. K. Solanki

The coming decade will see the routine use of solar data of unprecedented spatial and spectral resolution, time cadence, and completeness. To capitalize on the new (or soon to be available) facilities such as SDO, ATST and FASR, and the…

The solar coronal magnetic field produces solar activity, including extremely energetic solar flares and coronal mass ejections (CMEs). Knowledge of the structure and evolution of the magnetic field of the solar corona is important for…

Solar and Stellar Astrophysics · Physics 2015-06-22 Tilaye Tadesse , Thomas Wiegelmann , Peter MacNeice

Magnetic reconnection is believed to be the prime mechanism to trigger solar flares and accelerate electrons up to energies of MeV. In the classical two-dimensional reconnection model, the separation motion of chromospheric ribbons…

Solar and Stellar Astrophysics · Physics 2011-02-11 Chang Liu , Haimin Wang

A long-standing question in active galactic nucleus (AGN) research is how the corona is heated up to produce X-ray radiation much stronger than that arising from the viscous heating within the corona. In this paper, we carry out detailed…

High Energy Astrophysical Phenomena · Physics 2020-06-05 Huaqing Cheng , B. F. Liu , Jieying Liu , Zhu Liu , Erlin Qiao , Weimin Yuan

In solar physics, it is a big challenge to measure the magnetic fields directly from observations in the upper solar atmosphere, including the chromosphere and corona. Radio observations are regarded as the most feasible approach to…

Solar and Stellar Astrophysics · Physics 2022-06-22 Baolin Tan

Evidence of magnetic interaction between late-type stars and close-in giant planets is provided by the observations of stellar hot spots rotating synchronously with the planets and showing an enhancement of chromospheric and X-ray fluxes.…

Solar and Stellar Astrophysics · Physics 2015-05-13 A. F. Lanza

We obtain contemporaneous observations of the surface and corona of AB Dor using ground-based circularly polarised spectra from the Anglo-Australian Telescope and X-ray data from the Chandra satellite. The ground-based data are used to…