scholarly journals Oscillatory phenomena in a solar network region

2008 ◽  
Vol 4 (S257) ◽  
pp. 181-184
Author(s):  
Georgia Tsiropoula ◽  
Kostas Tziotziou ◽  
Pavol Schwartz ◽  
Petr Heinzel
Keyword(s):  
Transition Region ◽  
Temporal Variations ◽  
Spectral Lines ◽  
The Other ◽  
Propagation Characteristics ◽  
Heliospheric Observatory ◽  
Quiet Sun ◽  
Network Region ◽  
Multi Wavelength

AbstractWe examine oscillatory phenomena in a solar network region from multi-wavelength, observations obtained by the ground-based Dutch Open Telescope (DOT), and by instruments on the spacecraft Solar and Heliospheric Observatory (SoHO). The observations were obtained during a coordinated observing campaign on October 14, 2005. The temporal variations of the intensities and velocities in two distinct regions of the quiet Sun were investigated: one containing several dark mottles and the other several bright points defining the network boundaries (NB). The aim is to find similarities and/or differences in the oscillatory phenomena observed in these two regions and in different spectral lines formed from the chromosphere to the transition region, as well as propagation characteristics of waves.

scholarly journals Structure of sunspot light bridges in the chromosphere and transition region

2018 ◽  
Vol 609 ◽  
pp. A73 ◽  
Author(s):  
R. Rezaei
Keyword(s):  
Transition Region ◽  
Line Width ◽  
Solar Limb ◽  
Solar Radius ◽  
Spectral Lines ◽  
Quiet Sun ◽  
Hot Plasma ◽  
Emission Enhancement ◽  
Energy And Momentum ◽  
Far Ultraviolet

Context. Light bridges (LBs) are elongated structures with enhanced intensity embedded in sunspot umbra and pores. Aims. We studied the properties of a sample of 60 LBs observed with the Interface Region Imaging Spectrograph (IRIS). Methods. Using IRIS near- and far-ultraviolet spectra, we measured the line intensity, width, and Doppler shift; followed traces of LBs in the chromosphere and transition region (TR); and compared LB parameters with umbra and quiet Sun. Results. There is a systematic emission enhancement in LBs compared to nearby umbra from the photosphere up to the TR. Light bridges are systematically displaced toward the solar limb at higher layers: the amount of the displacement at one solar radius compares well with the typical height of the chromosphere and TR. The intensity of the LB sample compared to the umbra sample peaks at the middle/upper chromosphere where they are almost permanently bright. Spectral lines emerging from the LBs are broader than the nearby umbra. The systematic redshift of the Si iv line in the LB sample is reduced compared to the quiet Sun sample. We found a significant correlation between the line width of ions arising at temperatures from 3 × 104 to 1.5 × 105 K as there is also a strong spatial correlation among the line and continuum intensities. In addition, the intensity−line width relation holds for all spectral lines in this study. The correlations indicate that the cool and hot plasma in LBs are coupled. Conclusions. Light bridges comprise multi-temperature and multi-disciplinary structures extending up to the TR. Diverse heating sources supply the energy and momentum to different layers, resulting in distinct dynamics in the photosphere, chromosphere, and TR.

scholarly journals Rotating network jets in the quiet Sun as observed by IRIS

2018 ◽  
Vol 616 ◽  
pp. A99 ◽  
Author(s):  
P. Kayshap ◽  
K. Murawski ◽  
A. K. Srivastava ◽  
B. N. Dwivedi
Keyword(s):  
Statistical Analysis ◽  
Rotational Motion ◽  
High Speed ◽  
Rotational Velocity ◽  
Spectral Lines ◽  
The Other ◽  
Secondary Component ◽  
Doppler Velocity ◽  
Quiet Sun ◽  
Resolution Imaging

Aims. We perform a detailed observational analysis of network jets to understand their kinematics, rotational motion, and underlying triggering mechanism(s). We analyzed the quiet-Sun (QS) data. Methods. IRIS high-resolution imaging and spectral observations (slit-jaw images: Si IV 1400.0 Å; raster: Si IV 1393.75 Å) were used to analyze the omnipresent rotating network jets in the transition region (TR). In addition, we also used observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observation (SDO). Results. The statistical analysis of 51 network jets is performed to understand their various mean properties, e.g., apparent speed (140.16 ± 39.41 km s−1), length (3.16 ± 1.18 Mm), and lifetimes (105.49 ± 51.75 s). The Si IV 1393.75 Å line has a secondary component along with its main Gaussian, which is formed due to the high-speed plasma flows (i.e., network jets). The variation in Doppler velocity across these jets (i.e., blueshift on one edge and redshift on the other) signify the presence of inherited rotational motion. The statistical analysis predicts that the mean rotational velocity (i.e., ΔV) is 49.56 km s−1. The network jets have high-angular velocity in comparison to the other class of solar jets. Conclusions. The signature of network jets is inherited in TR spectral lines in terms of the secondary component of the Si IV 1393.75 Å line. The rotational motion of network jets is omnipresent, which is reported first for this class of jet-like features. The magnetic reconnection seems to be the most favorable mechanism for the formation of these network jets.

SUMER Observations of the Quiet‐Sun Transition Region

1999 ◽  
Vol 512 (2) ◽  
pp. 992-1005 ◽  
Author(s):  
N. W. Griffiths ◽  
G. H. Fisher ◽  
D. T. Woods ◽  
O. H. W. Siegmund
Keyword(s):  
Transition Region ◽  
Quiet Sun

Spatial and temporal variations in acoustic propagation characteristics at the new england shelfbreak front

2003 ◽  
Vol 28 (1) ◽  
pp. 129-150 ◽  
Author(s):  
J.F. Lynch ◽  
A.E. Newhall ◽  
B. Sperry ◽  
G. Gawarkiewicz ◽  
A. Fredricks ◽  
...  
Keyword(s):  
New England ◽  
Acoustic Propagation ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Propagation Characteristics

scholarly journals Observations of the Quiet Sun with 6″ Resolution

1980 ◽  
Vol 86 ◽  
pp. 53-55
Author(s):  
M. R. Kundu ◽  
A. P. Rao ◽  
F. T. Erskine ◽  
J. D. Bregman
Keyword(s):  
High Resolution ◽  
Radio Emission ◽  
Transition Region ◽  
Spatial Resolution ◽  
Radio Telescope ◽  
Solar Radio ◽  
High Spatial Resolution ◽  
Solar Radio Emission ◽  
Quiet Sun ◽  
Millimeter Wavelengths

Solar radio emission at centimeter and millimeter wavelengths originates in the chromosphere and transition region and is a useful probe for the temperature and density in these regions. High spatial resolution observations of the quiet sun provide valuable information on the structure of the solar atmosphere. We have performed high resolution (~ 6″ (E-W) x 15″ (N-S)) observations at 6 cm with the Westerbork Synthesis Radio Telescope (WSRT) in June 1976 in order to search for the radio analog of the supergranulation network and to study the extent and symmetry of limb brightening. The use of the WSRT for high spatial resolution solar mapping has been described by Bregman and Felli (1976), Kundu et al. (1977), and others.

scholarly journals Emergence of small-scale magnetic flux in the quiet Sun

2020 ◽  
Vol 633 ◽  
pp. A67 ◽  
Author(s):  
I. Kontogiannis ◽  
G. Tsiropoula ◽  
K. Tziotziou ◽  
C. Gontikakis ◽  
C. Kuckein ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Morphological Characteristics ◽  
Small Scale ◽  
X Rays ◽  
Coronal Emission ◽  
Quiet Sun ◽  
Temperature Regimes ◽  
Multi Wavelength ◽  
Modelling Studies

Context. We study the evolution of a small-scale emerging flux region (EFR) in the quiet Sun, from its emergence in the photosphere to its appearance in the corona and its decay. Aims. We track processes and phenomena that take place across all atmospheric layers; we explore their interrelations and compare our findings with those from recent numerical modelling studies. Methods. We used imaging as well as spectral and spectropolarimetric observations from a suite of space-borne and ground-based instruments. Results. The EFR appears in the quiet Sun next to the chromospheric network and shows all morphological characteristics predicted by numerical simulations. The total magnetic flux of the region exhibits distinct evolutionary phases, namely an initial subtle increase, a fast increase with a Co-temporal fast expansion of the region area, a more gradual increase, and a slow decay. During the initial stages, fine-scale G-band and Ca II H bright points coalesce, forming clusters of positive- and negative-polarity in a largely bipolar configuration. During the fast expansion, flux tubes make their way to the chromosphere, pushing aside the ambient magnetic field and producing pressure-driven absorption fronts that are visible as blueshifted chromospheric features. The connectivity of the quiet-Sun network gradually changes and part of the existing network forms new connections with the newly emerged bipole. A few minutes after the bipole has reached its maximum magnetic flux, the bipole brightens in soft X-rays forming a coronal bright point. The coronal emission exhibits episodic brightenings on top of a long smooth increase. These coronal brightenings are also associated with surge-like chromospheric features visible in Hα, which can be attributed to reconnection with adjacent small-scale magnetic fields and the ambient quiet-Sun magnetic field. Conclusions. The emergence of magnetic flux even at the smallest scales can be the driver of a series of energetic phenomena visible at various atmospheric heights and temperature regimes. Multi-wavelength observations reveal a wealth of mechanisms which produce diverse observable effects during the different evolutionary stages of these small-scale structures.

scholarly journals Statistical Features of the Quiet Sun in EUV

2001 ◽  
Vol 203 ◽  
pp. 416-418
Author(s):  
A. Pauluhn ◽  
S. K. Solanki ◽  
I. Rüedi ◽  
E. Landi ◽  
U. Schühle
Keyword(s):  
Lognormal Distribution ◽  
Distribution Functions ◽  
Spectral Lines ◽  
Emission Lines ◽  
Statistical Features ◽  
Frequency Distributions ◽  
Quiet Sun ◽  
Euv Emission ◽  
The Past ◽  
Radiance Distribution

Frequency distributions of the intensities of EUV emission lines in the quiet Sun have in the past usually been modelled using two Gaussians. Here we test this and other distribution functions against observed distributions with exceptional statistics. The data were obtained in a number of spectral lines observed with CDS and SUMER. We show that the frequency distribution of the radiance is best modelled by a lognormal distribution. The fact that the radiance distribution of the quiet Sun including the network and the intranetwork is better reproduced by a single lognormal distribution function than by two Gaussians suggests that the same heating processes are acting in both types of features.

scholarly journals A Flare on AD Leo observed in Optical, UV and Microwaves

1989 ◽  
Vol 104 (2) ◽  
pp. 63-66
Author(s):  
P.B. Byrne ◽  
D.E. Gary
Keyword(s):  
Emission Line ◽  
Transition Region ◽  
Photometric Observation ◽  
The Other ◽  
Optical Flare

SummaryWe report a simultaneous IUE, VLA and ground-based photometric observation of a flare on the dMe star, AD Leo, on 2nd February 1903. The optical flare was extremely impulsive, lasting in total only about 3 mins. A relatively longlived 6 cm flare was observed with the VLA which was initially 100% polarized. An IUE spectrum, taken ≈ 8 min after the onset of the optical U band flare, shows motu than a factor of 2 increase in the Ha II λ 1640Å emission line. The other mid-transition region lines such as C IV λλ154B/52Å show almost no response.

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