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Small flares frequently occur in the quiet Sun. Previous studies have noted that they share many common characteristics with typical solar flares in active regions. However, their similarities and differences are not fully understood,…

Solar and Stellar Astrophysics · Physics 2023-05-03 Yuji Kotani , Takako T. Ishii , Daiki Yamasaki , Kenichi Otsuji , Kiyoshi Ichimoto , Ayumi Asai , Kazunari Shibata

Context. An analysis of the oscillations above sunspots was carried out using simultaneous ground-based and Solar Dynamics Observatory (SDO) observations (SiI 10827A, HeI 10830A, FeI 6173A, 1700A, HeII 304A, FeIX 171A). Aims. Investigation…

Solar and Stellar Astrophysics · Physics 2014-11-25 N. I. Kobanov , A. A. Chelpanov , D. Y. Kolobov

The velocity pattern of a fan loop structure within a solar active region over the temperature range 0.15-1.5 MK is derived using data from the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. The loop is aligned towards the…

Solar and Stellar Astrophysics · Physics 2015-05-28 P. R. Young , B. O'Dwyer , H. E. Mason

Despite intensive studies of kink oscillations of coronal loops in the last decade, a large scale statistically significant investigation of the oscillation parameters has not been made using data from the Solar Dynamics Observatory (SDO).…

Solar and Stellar Astrophysics · Physics 2016-01-13 C. R. Goddard , G. Nistic`o , V. M. Nakariakov , I. V. Zimovets

We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer and HXR measurements acquired with RHESSI during an M-class flare. During the flare impulsive phase, we observe no significant flows in the cooler…

Solar and Stellar Astrophysics · Physics 2016-03-09 P. Gömöry , A. M. Veronig , Y. Su , M. Temmer , J. K. Thalmann

In the last 30 years, the existence of small and cool magnetic loops (height < 8 Mm, T < 10^5 K) has been proposed and debated to explain the increase of the DEM (differential emission measure) towards the chromosphere. We present…

Solar and Stellar Astrophysics · Physics 2015-06-03 C. Sasso , V. Andretta , D. Spadaro , R. Susino

Strongly damped Doppler shift oscillations are observed frequently associated with flarelike events in hot coronal loops. In this paper, a review of the observed properties and the theoretical modeling is presented. Statistical measurements…

Solar and Stellar Astrophysics · Physics 2014-04-24 Tongjiang Wang

Daily differential emission measure (DEM) distributions of the solar corona are derived from spectra obtained by the Extreme-ultraviolet Variability Experiment (EVE) over a 4-year period starting in 2010 near solar minimum and continuing…

Solar and Stellar Astrophysics · Physics 2020-09-16 Samuel J. Schonfeld , Stephen M. White , Rachel A. Hock-Mysliwiec , R. T. James McAteer

Previous solar observations have shown that coronal loops near 1 MK are difficult to reconcile with simple heating models. These loops have lifetimes that are long relative to a radiative cooling time, suggesting quasi-steady heating. The…

The solar chromosphere hosts a wide variety of transients, including dynamic fibrils (DFs) that are characterised as elongated, jet-like features seen in active regions, often through H$\alpha$ diagnostics. So far, these features have been…

In this paper, we present the observations of two successive fast-mode extreme ultraviolet (EUV) wave events observed on 2016 July 23. Both fast-mode waves were observed by the Atmospheric Imaging Assembly (AIA) instrument on board the…

Solar and Stellar Astrophysics · Physics 2018-08-22 R. Chandra , P. F. Chen , R. Joshi , B. Joshi , B. Schmieder

Solar flare emission at X-ray and extreme ultraviolet (EUV) energies can cause substantial enhancements in the electron density in the Earth's lower ionosphere. It is now become clear that flares exhibit quasi-periodic pulsations with…

We have studied the relationship between the velocity and temperature of a solar EUV jet. The highly accelerated jet occurred in the active region NOAA 10960 on 2007 June 5. Multi-wavelength spectral observations with EIS/Hinode allow us to…

Solar and Stellar Astrophysics · Physics 2015-06-11 Y. Matsui , T. Yokoyama , N. Kitagawa , S. Imada

The last solar minimum has been unusually quiet compared to the previous minima (since space-based radiometric measurements are available). The Sun's magnetic flux was substantially lower during this minimum. Some studies also show that the…

Solar and Stellar Astrophysics · Physics 2015-09-02 F. Shakeri , L. Teriaca , S. K. Solanki

The nanoflare model of coronal heating is one of the most successful scenarios to explain, within a single framework, the diverse set of coronal observations available with the present instrument resolutions. The model is based on the idea…

Solar and Stellar Astrophysics · Physics 2022-10-06 Marcelo López Fuentes , James A. Klimchuk

Two sequences of solar images obtained by the Transition Region and Coronal Explorer in three UV passbands are studied using wavelet and Fourier analysis and compared to the photospheric magnetic flux measured by the Michelson Doppler…

Three-minute oscillations are a common phenomenon in the solar chromosphere above a sunspot. Oscillations can be affected by the energy release process related to solar flares. In this paper, we report on an enhanced oscillation in flare…

Solar and Stellar Astrophysics · Physics 2023-11-30 Ya Wang , Lyndsay Fletcher , Sargam Mulay , Haisheng Ji , Wenda Cao

Context: Flux emergence in the solar atmosphere is a complex process that causes a release of magnetic energy as heat and acceleration of solar plasma at a variety of spatial scales. Methods: We analysed imaging spectropolarimetric data…

Observational evidence for gentle chromospheric evaporation during the impulsive phase of a C9.1 solar flare is presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Coronal Diagnostic Spectrometer on…

Brightenings observed in the solar extreme-ultraviolet (EUV) images are generally interpreted as signatures of micro- or nanoflares occurring at the transition region or coronal temperatures. Recent observations with the Extreme Ultraviolet…

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