scholarly journals A Search for the Counterparts of Quiet-Sun Radio Transients in Extreme Ultraviolet Data

Solar Physics ◽  
2021 ◽  
Vol 296 (8) ◽  
Author(s):  
Surajit Mondal
Keyword(s):  
Extreme Ultraviolet ◽  
Quiet Sun ◽  
Radio Transients

scholarly journals OBSERVATIONS AND MODELING OF THE EMERGING EXTREME-ULTRAVIOLET LOOPS IN THE QUIET SUN AS SEEN WITH THESOLAR DYNAMICS OBSERVATORY

2013 ◽  
Vol 768 (1) ◽  
pp. 32 ◽  
Author(s):  
L. P. Chitta ◽  
R. Kariyappa ◽  
A. A. van Ballegooijen ◽  
E. E. DeLuca ◽  
S. S. Hasan ◽  
...  
Keyword(s):  
Extreme Ultraviolet ◽  
Quiet Sun

scholarly journals Time Variability of the “Quiet” Sun Observed withTRACE. I. Instrumental Effects, Event Detection, and Discrimination of Extreme‐Ultraviolet Microflares

2000 ◽  
Vol 535 (2) ◽  
pp. 1027-1046 ◽  
Author(s):  
Markus J. Aschwanden ◽  
Richard W. Nightingale ◽  
Ted D. Tarbell ◽  
C. J. Wolfson
Keyword(s):  
Event Detection ◽  
Extreme Ultraviolet ◽  
Time Variability ◽  
Instrumental Effects ◽  
Quiet Sun

Measuring Active and Quiet-Sun Coronal Plasma Properties with Extreme-Ultraviolet Spectra from SERTS

1996 ◽  
Vol 106 ◽  
pp. 143 ◽  
Author(s):  
Jeffrey W. Brosius ◽  
Joseph M. Davila ◽  
Roger J. Thomas ◽  
Brunella C. Monsignori-Fossi
Keyword(s):  
Extreme Ultraviolet ◽  
Coronal Plasma ◽  
Plasma Properties ◽  
Quiet Sun ◽  
Ultraviolet Spectra

Transient small-scale brightenings in the quiet Sun corona: a model for "campfires" observed with Solar Orbiter

2021 ◽  
Author(s):  
Yajie Chen ◽  
Damien Przybylski ◽  
Hardi Peter ◽  
Hui Tian
Keyword(s):  
Convection Zone ◽  
Extreme Ultraviolet ◽  
Small Scale ◽  
Coronal Emission ◽  
Lower Corona ◽  
Quiet Sun ◽  
Self Consistent ◽  
Before And After ◽  
Field Lines ◽  
The Magnetic Field

<div> <div> <div> <p>Recent observations by the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter have revealed prevalent small-scale transient brightenings in the quiet solar corona termed campfires. To understand the generation mechanism of these coronal brightenings, we constructed a self- consistent and time-dependent quiet-Sun model extending from the upper convection zone to the lower corona using a realistic 3D radiation MHD simulation. From the model we have synthesized the coronal emission in the EUI 174 Å passband. We identified several transient coronal brightenings similar to those in EUI observations. The size and lifetime of these coronal brightenings are 2–4 Mm and ∼2 min, respectively. These brightenings are located at a height of 2–4 Mm above the photosphere, and the surrounding plasma is often heated above 1 MK. These findings are consistent with the observational characterisation of the campfires. Through a comparison of the magnetic field structures before and after the occurrence of brightenings, we conclude that these coronal brightenings are generated by component magnetic reconnection between interacting bundles of field lines or the relaxation of highly twisted flux ropes. Occurring in the coronal part of the atmosphere, these events show no measurable signature in the photosphere. These transient coronal brightenings may play an important role in heating of the local coronal plasma.</p> </div> </div> </div>

Solving the Discrepancy between the Extreme‐Ultraviolet and Microwave Observations of the Quiet Sun

2003 ◽  
Vol 589 (2) ◽  
pp. 1054-1061 ◽  
Author(s):  
E. Landi ◽  
F. Chiuderi Drago
Keyword(s):  
Extreme Ultraviolet ◽  
Quiet Sun

scholarly journals A persistent quiet-Sun small-scale tornado

2018 ◽  
Vol 618 ◽  
pp. A51 ◽  
Author(s):  
K. Tziotziou ◽  
G. Tsiropoula ◽  
I. Kontogiannis ◽  
E. Scullion ◽  
J. G. Doyle
Keyword(s):  
Vortex Flow ◽  
Extreme Ultraviolet ◽  
Spectral Lines ◽  
Small Scale ◽  
Large Radius ◽  
Vortex Flows ◽  
Line Profiles ◽  
Quiet Sun ◽  
Long Duration ◽  
Wide Range

Context. Vortex flows have been extensively observed over a wide range of spatial and temporal scales in different spectral lines, and thus layers of the solar atmosphere, and have been widely found in numerical simulations. However, signatures of vortex flows have only recently been reported in the wings of the Hα, but never so far in the Hα line centre. Aims. We investigate the appearance, characteristics, substructure, and dynamics of a 1.7 h persistent vortex flow observed from the ground and from space in a quiet-Sun region in several lines/channels covering all atmospheric layers from the photosphere up to the low corona. Methods. We use high spatial and temporal resolution CRisp Imaging SpectroPolarimeter (CRISP) observations in several wavelengths along the Hα and Ca II 8542 Å line profiles, simultaneous Atmospheric Imaging Assembly (AIA) observations in several Ultraviolet (UV) and Extreme ultraviolet (EUV) channels and Helioseismic and Magnetic Imager (HMI) magnetograms to study a persistent vortex flow located at the south solar hemisphere. Doppler velocities were derived from the Hα line profiles. Our analysis involves visual inspection and comparison of all available simultaneous/near-simultaneous observations and detailed investigation of the vortex appearance, characteristics and dynamics using time slices along linear and circular slits. Results. The most important characteristic of the analysed clockwise rotating vortex flow is its long duration (at least 1.7 h) and its large radius (~3″). The vortex flow shows different behaviours in the different wavelengths along the Hα and Ca II 8542 Å profiles reflecting the different formation heights and mechanisms of the two lines. Ground-based observations combined with AIA observations reveal the existence of a funnel-like structure expanding with height, possibly rotating rigidly or quasi-rigidly. However, there is no clear evidence that the flow is magnetically driven as no associated magnetic bright points have been observed in the photosphere. Hα and Ca II 8542 Å observations also reveal significant substructure within the flow, manifested as several individual intermittent chromospheric swirls with typical sizes and durations. They also exhibit a wide range of morphological patterns, appearing as dark absorbing features, associated mostly with mean upwards velocities around 3 km s−1 and up to 8 km s−1, and occupying on average ~25% of the total vortex area. The radial expansion of the spiral flow occurs with a mean velocity of ~3 km s−1, while its dynamics can be related to the dynamics of a clockwise rigidly rotating logarithmic spiral with a swinging motion that is, however, highly perturbed by nearby flows associated with fibril-like structures. A first rough estimate of the rotational period of the vortex falls in the range of 200–300 s. Conclusions. The vortex flow resembles a small-scale tornado in contrast to previously reported short-lived swirls and in analogy to persistent giant tornadoes. It is unclear whether the observed substructure is indeed due to the physical presence of individual intermittent, recurring swirls or a manifestation of wave-related instabilities within a large vortex flow. Moreover, we cannot conclusively demonstrate that the long duration of the observed vortex is the result of a central swirl acting as an “engine” for the vortex flow, although there is significant supporting evidence inferred from its dynamics. It also cannot be excluded that this persistent vortex results from the combined action of several individual smaller swirls further assisted by nearby flows or that this is a new case in the literature of a hydrodynamically driven vortex flow.

A Discussion on the physics of the solar atmosphere - The quiet Sun in the extreme ultraviolet

1976 ◽  
Vol 281 (1304) ◽  
pp. 319-329 ◽  
Keyword(s):  
Transition Region ◽  
Solar Atmosphere ◽  
Spherical Symmetry ◽  
Extreme Ultraviolet ◽  
Coronal Holes ◽  
Intensity Data ◽  
Periodic Oscillations ◽  
Quiet Sun ◽  
Temperature Range ◽  
Ultraviolet Spectrometer

Observations of the quiet Sun with the Harvard extreme ultraviolet spectrometer on the Skylab mission are reported for the chromosphere, transition region, and corona. The changing structure of the network is examined over the temperature range from 10 4 to 1.5 x 10 6 K, and the distribution of intensities in the cell interiors and the network examined from the standpoint of creating characteristic models. Observations of traces of periodic oscillations at 300 s in the cells for T ⩽ 2 x 10 4 is reported together with the absence of any periodic contributions at higher temperatures or periodic effects at any height in the network elements. Frequent non-periodic brightenings are observed, however, and their characteristics discussed. Observations of the increased thickness of the transition region in coronal holes, as well as other properties are discussed in limited detail. Observations of the centre-to-limb behaviour of transition region and coronal lines are used to construct coronal models, and the assumptions of spherical symmetry evaluated from the intensity data. The effects of spicules on the limb and disk data are discussed in relation to the observations.

scholarly journals Modeling images of the Quiet Sun in the extreme ultraviolet

2007 ◽  
Author(s):  
Pierre Chainais ◽  
Véronique Delouille ◽  
Jean-François Hochedez
Keyword(s):  
Extreme Ultraviolet ◽  
Quiet Sun
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