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The dynamics of horizontal plasma flows during the first hours of the emergence of active region magnetic flux in the solar photosphere have been analyzed using SOHO/MDI data. Four active regions emerging near the solar limb have been…

Solar and Stellar Astrophysics · Physics 2017-05-01 A. Khlystova

Superhalo electrons appear to be continuously present in the interplanetary medium, even at very quiet times, with a power-law spectrum at energies above $\sim$2 keV. Here we numerically investigate the generation of superhalo electrons by…

Solar and Stellar Astrophysics · Physics 2016-05-26 L. -P. Yang , L. -H. Wang , J. -S. He , C. -Y. Tu , S. -H. Zhang , L. Zhang , X. -S. Feng

New calculations of radiative rates and electron impact excitation cross sections for Fe XI are used to derive emission line intensity ratios involving 3s^23p^4 - 3s^23p^33d transitions in the 180-223 A wavelength range. These ratios are…

Recent high-resolution solar observations have unveiled the presence of small-scale loop-like structures in the lower solar atmosphere, often referred to as unresolved fine structures, low-lying loops, and miniature hot loops. These…

Solar and Stellar Astrophysics · Physics 2025-03-14 Annu Bura , Tanmoy Samanta , Alphonse Sterling , Yajie Chen , Jayant Joshi , Vasyl Yurchyshyn , Ronald L. Moore

Coronal upflows at the edges of active regions (AR), which are a possible source of slow solar wind, have been found to connect with dynamics in the transition region. To infer at what scale transition region dynamics connect to AR upflows,…

Solar and Stellar Astrophysics · Physics 2021-09-08 Zhenghua Huang , Lidong Xia , Hui Fu , Zhenyong Hou , Ziyuan Wang

Spectroscopic observations with the EUV Imaging Spectrometer (EIS) on Hinode have revealed large areas of high speed outflows at the periphery of many solar active regions. These outflows are of interest because they may connect to the…

Solar and Stellar Astrophysics · Physics 2015-05-19 Harry P. Warren , Ignacio Ugarte-Urra , Peter R. Young , Guillermo Stenborg

We study the dynamics of low-lying cool loop systems for three datasets as observed by the Interface Region Imaging Spectrograph (IRIS). Radiances, Doppler shifts and line widths are investigated in and around observed cool loop systems…

Solar and Stellar Astrophysics · Physics 2019-03-27 Yamini K. Rao , Abhishek K. Srivastava , Pradeep Kayshap , Klaus Wilhelm , Bhola N. Dwivedi

A well known behavior of EUV light curves of discrete coronal loops is that the peak intensities of cooler channels or spectral lines are reached at progressively later times than hotter channels. This time lag is understood to be the…

Solar and Stellar Astrophysics · Physics 2015-06-04 Nicholeen M. Viall , James A. Klimchuk , NASA Goddard Space Flight Center

The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random…

Solar and Stellar Astrophysics · Physics 2016-01-22 R. B. Dahlburg , G. Einaudi , B. D. Taylor , I. Ugarte-Urra , H. P. Warren , A. F. Rappazzo , M. Velli

Measurements of the structure of hexagonal RMnO3 (R=rare earths (Ho) and Y) for temperatures significantly above the ferroelectric transition temperature (TFE) were conducted to determine the nature of the transition. The local and long…

Materials Science · Physics 2015-05-30 T. A. Tyson , T. Wu , H. Y. Chen , J. Bai , K. H. Ahn , K. I. Pandya , S. B. Kim , S. -W. Cheong

Observational and theoretical evidence suggests that coronal heating is impulsive and occurs on very small cross-field spatial scales. A single coronal loop could contain a hundred or more individual strands that are heated…

Astrophysics · Physics 2009-11-13 J. A. Klimchuk , S. Patsourakos , P. J. Cargill

Coronal loops interconnecting two active regions, called as interconnecting loops (ILs), are prominent large-scale structures in the solar atmosphere. They carry a significant amount of magnetic flux, therefore are considered to be an…

Solar and Stellar Astrophysics · Physics 2018-06-27 Guohui Du , Yao Chen , Chunming Zhu , Chang Liu , Lili Ge , Bing Wang , Chuanyang Li , Haimin Wang

We use UV spectral observations of active regions with the Interface Region Imaging Spectrograph (IRIS) to investigate the properties of the coronal FeXII 1349.4A emission at unprecedented high spatial resolution (~0.33"). We find that by…

Solar and Stellar Astrophysics · Physics 2016-08-17 Paola Testa , Bart De Pontieu , Viggo Hansteen

A qualitative analysis is given to the data on the full magnetic and velocity vector fields in a growing sunspot group, recorded nearly simultaneously with the Solar Optical Telescope on the Hinode satellite. Observations of a young bipolar…

Solar and Stellar Astrophysics · Physics 2016-03-22 A. V. Getling , R. Ishikawa , A. A. Buchnev

Recent observations in extreme-ultraviolet (EUV) wavelengths reveal an EUV late phase in some solar flares that is characterized by a second peak in warm coronal emissions ($\sim3$~MK) several tens of minutes to a few hours after the soft…

Solar and Stellar Astrophysics · Physics 2018-05-02 Yu Dai , Mingde Ding

In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon that can occur when the heating is both highly-stratified and quasi-constant. Unambiguous observational identification of TNE would thus permit to strongly constrain…

Solar and Stellar Astrophysics · Physics 2017-02-08 Clara Froment , Frédéric Auchère , Guillaume Aulanier , Zoran Mikić , Karine Bocchialini , Eric Buchlin , Jacques Solomon

The first self-consistent simulations of electron acceleration during magnetic reconnection in a macroscale system are presented. Consistent with solar flare observations the spectra of energetic electrons take the form of power-laws that…

Penumbral transient brightening events have been attributed to magnetic reconnection episodes occurring in the low corona. We investigated the trigger mechanism of these events in active region NOAA 12546 by using multi-wavelength…

Solar and Stellar Astrophysics · Physics 2020-02-26 M. Murabito , S. L. Guglielmino , I. Ermolli , M. Stangalini , F. Giorgi

We analyzed and modeled an M1.2 non-eruptive solar flare on 2011 September 9. The flare exhibits a strong late-phase peak of the warm coronal emissions ($\sim$3~MK) of extreme-ultraviolet (EUV), with peak emission over 1.3 times that of the…

Solar and Stellar Astrophysics · Physics 2018-08-29 Yu Dai , Mingde Ding , Weiguo Zong , Kai E. Yang

The acceleration mechanism of EUV/X-ray jets is still unclear. For the most part, there are two candidates for the mechanism. One is magnetic reconnection, and the other is chromospheric evaporation. We observed a relatively compact X-ray…

Solar and Stellar Astrophysics · Physics 2019-06-19 Toshiki Kawai , Natsuo Kanda , Shinsuke Imada