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Context. Transmission spectroscopy is one of the most powerful techniques to characterize transiting exoplanets since it allows to measure the abundance of the atomic and molecular species in the planetary atmosphere. However, the stellar…

Solar and Stellar Astrophysics · Physics 2023-12-11 G. Canocchi , K. Lind , C. Lagae , A. G. M. Pietrow , A. M. Amarsi , D. Kiselman , O. Andriienko , H. J. Hoeijmakers

Solar prominences contain a significant amount of neutral species. The dynamics of the ionised and neutral fluids composing the prominence plasma can be slightly different if the collisional coupling is not strong enough. Large-scale…

Solar and Stellar Astrophysics · Physics 2023-11-07 S. J. González Manrique , E. Khomenko , M. Collados , C. Kuckein , T. Felipe , P. Gömöry

We observe plasma flows in cool loops using the Slit-Jaw Imager (SJI) onboard the Interface Region Imaging Spectrometer (IRIS). Huang et al. (2015) observed unusually broadened Si IV 1403 angstrom line profiles at the footpoints of such…

Solar and Stellar Astrophysics · Physics 2020-05-27 A. K. Srivastava , Yamini K. Rao , P. Konkol , K. Murawski , M. Mathioudakis , Sanjiv K. Tiwari , E. Scullion , J. G. Doyle , B. N. Dwivedi

Previous studies analyzing the evanescent nature of acoustic waves in the lower solar atmosphere, up to 300\,km above the photosphere, have shown an unexpected phase shift of an order of 1\,s between different heights. Those studies…

Solar and Stellar Astrophysics · Physics 2023-06-14 M. Waidele , Junwei Zhao , I. N. Kitiashvili

Spectral line widths are often observed to be larger than can be accounted for by thermal and instrumental broadening alone. This excess broadening is a key observational constraint for both nanoflare and wave dissipation models of coronal…

Solar and Stellar Astrophysics · Physics 2016-03-23 David H. Brooks , Harry P. Warren

We find evidence for the first observation of the parametric decay instability (PDI) in the lower solar atmosphere. Specifically, we find that the power spectrum of density fluctuations near the solar transition region resembles the power…

Solar and Stellar Astrophysics · Physics 2022-07-20 Michael Hahn , Xiangrong Fu , Daniel Wolf Savin

The detection of Earth-like planets with the radial-velocity method is currently limited by the presence of stellar activity signatures. On rotational timescales, spots and plages (or faculae) are known to introduce different RV signals,…

Solar and Stellar Astrophysics · Physics 2023-10-25 M. Cretignier , A. G. M. Pietrow , S. Aigrain

In this paper, we analyze the high-resolution UV spectra for a C1.7 solar flare (SOL2017-09-09T06:51) observed by the \textit{Interface Region Imaging Spectrograph} (\textit{IRIS}). {We focus on the spectroscopic observations at the…

Solar and Stellar Astrophysics · Physics 2020-12-02 Yi-An Zhou , Y. Li , M. D. Ding , Jie Hong , Ke Yu

The first spectroscopic observations of cool Mg II loops above the solar limb observed by NASA's Interface Region Imaging Spectrograph ({\it IRIS}; \cite{IRIS}) are presented. During the observation period IRIS is pointed off-limb allowing…

Solar and Stellar Astrophysics · Physics 2014-09-02 L. K. Harra , S. A. Matthews , D. M. Long , G. A. Doschek , B. De Pontieu

The CLASP2 (Chromospheric LAyer SpectroPolarimeter 2) sounding rocket mission was launched on 2019 April 11. CLASP2 measured the four Stokes parameters of the Mg II h & k spectral region around 2800 Angstroms along a 200 arcsecond slit at…

Small-scale magnetic fields can be observed on the Sun in high resolution G-band filtergrams as magnetic bright points (MBPs). We study Hinode/ Solar Optical Telescope (SOT) longitude and latitude scans of the quiet solar surface taken in…

Solar and Stellar Astrophysics · Physics 2012-12-07 D. Utz , A. Hanslmeier , A. Veronig , O. Kühner , R. Muller , J. Jurčák , B. Lemmerer

We have analyzed the local acoustic spectra of small regions over the solar surface at different locations from disk center to limb via the technique of ring diagrams. It is found that the frequency shifts between velocity and intensity is…

Astrophysics · Physics 2007-05-23 S. C. Tripathy , Kiran Jain , Frank Hill , C. G. Toner

A new generation of Ge-based high-resolution gamma-ray spectrometers has allowed accurate measurements to be made of the profiles, widths and energies of the gamma-ray lines emitted in the impulsive phases of solar flares. Here we present…

Astrophysics · Physics 2009-11-11 M. J. Harris , V. Tatischeff , J. Kiener , M. Gros , G. Weidenspointner

We investigate numerically the time evolution of velocity and magnetic field fluctuations in a coronal loop, focusing on the dynamics due to both phase mixing and turbulent cascade. The intensity, doppler velocity and non-thermal broadening…

IRIS data allow us to study the solar transition region (TR) with an unprecedented spatial resolution of 0.33 arcsec. On 2013 August 30, we observed bursts of high Doppler shifts suggesting strong supersonic downflows of up to 200 km/s and…

Major solar flares are prone to occur in active region atmospheres associated with large, complex, dynamically-evolving sunspots. This points to the importance of monitoring the evolution of starspots, not only in visible but also in ultra…

Solar and Stellar Astrophysics · Physics 2020-10-14 Shin Toriumi , Vladimir S. Airapetian , Hugh S. Hudson , Carolus J. Schrijver , Mark C. M. Cheung , Marc L. DeRosa

The origin of nonthermal broadening in solar spectra is one of the long-standing questions in solar physics. Various processes have been invoked - including unresolved flows, waves, and turbulent processes - but definitive answers are…

Solar and Stellar Astrophysics · Physics 2024-10-28 Kyuhyoun Cho , Bart De Pontieu , Paola Testa

Observation of Interplanetary Scintillation (IPS) provides an important and effective way to study the solar wind and the space weather. A series of IPS observations were conducted by the Five-hundred-meter Aperture Spherical radio…

Solar and Stellar Astrophysics · Physics 2022-08-03 Li-Jia Liu , Bo Peng , Lei Yu , Bin Liu , Ji-Guang Lu , Ye-Zhao Yu , Hong-Wei Xi , Ming Xiong , O. Chang

We investigate the properties and relationship between Doppler-velocity fluctuations and intensity fluctuations in the off-limb quiet Sun corona. These are expected to reflect the properties of Alfvenic and compressive waves, respectively.…

Solar and Stellar Astrophysics · Physics 2025-03-21 Michael Hahn , Xiangrong Fu , Stefan J. Hofmeister , Yifan Huang , Alexandros Koukras , Daniel Wolf Savin

We derive formulae connecting the frequency variations in the spectrum of solar oscillations to the dynamical quantities that are expected to change over the solar activity cycle. This is done for both centroids and the asymmetric part of…

Astrophysics · Physics 2009-11-10 W. A. Dziembowski , P. R. Goode