Fluid motions in the solar chromosphere-corona transition region. I - Line widths and Doppler shifts for C IV

1983 ◽  
Vol 265 ◽  
pp. 519 ◽  
Author(s):  
R. G. Athay ◽  
J. B. Gurman ◽  
W. Henze ◽  
R. A. Shine
Keyword(s):  
Transition Region ◽  
Solar Chromosphere ◽  
Doppler Shifts ◽  
Region I ◽  
Line Widths

V. Dynamics of the Chromosphere and Transition Region

1985 ◽  
Vol 19 (1) ◽  
pp. 108-110
Author(s):  
R. Grant Athay
Keyword(s):  
Transition Region ◽  
Velocity Component ◽  
Sound Speed ◽  
Thermal Velocity ◽  
Doppler Shifts ◽  
Line Widths ◽  
Lower Transition ◽  
Increasing Temperature ◽  
Line Positions

One of the more interesting aspects of the chromosphere-corona transition region is its tendency to exhibit large Doppler shifts. Both the non-thermal velocity component of line widths and the velocity displacement of line positions tend to maximize at temperatures near 105 K. The increase in velocity amplitudes with increasing temperatures below 105 K is readily understood in terms of the increasing sound speed and decreasing densities associated with the outwardly increasing temperature. Why the observed velocity amplitudes should decrease at still higher temperatures is not at all clear, however, and it seems very likely that this phenomenon is indicative of fundamental differences in the dynamics of the upper transition region and corona from those in the lower transition region and chromosphere.

scholarly journals Chromospheric counterparts of solar transition region unresolved fine structure loops

2018 ◽  
Vol 611 ◽  
pp. L6 ◽  
Author(s):  
Tiago M. D. Pereira ◽  
Luc Rouppe van der Voort ◽  
Viggo H. Hansteen ◽  
Bart De Pontieu
Keyword(s):  
Transition Region ◽  
Current Knowledge ◽  
Solar Limb ◽  
Theoretical Models ◽  
Solar Chromosphere ◽  
Solar Transition Region ◽  
Solar Transition ◽  
Heating And Cooling ◽  
Doppler Shifts ◽  
New Information

Low-lying loops have been discovered at the solar limb in transition region temperatures by the Interface Region Imaging Spectrograph (IRIS). They do not appear to reach coronal temperatures, and it has been suggested that they are the long-predicted unresolved fine structures (UFS). These loops are dynamic and believed to be visible during both heating and cooling phases. Making use of coordinated observations between IRIS and the Swedish 1-m Solar Telescope, we study how these loops impact the solar chromosphere. We show for the first time that there is indeed a chromospheric signal of these loops, seen mostly in the form of strong Doppler shifts and a conspicuous lack of chromospheric heating. In addition, we find that several instances have a inverse Y-shaped jet just above the loop, suggesting that magnetic reconnection is driving these events. Our observations add several puzzling details to the current knowledge of these newly discovered structures; this new information must be considered in theoretical models.

scholarly journals The structure of the lower solar chromosphere in undisturbed and active regions

1968 ◽  
Vol 35 ◽  
pp. 255-258 ◽  
Author(s):  
E. Dubov
Keyword(s):  
Active Regions ◽  
Brightness Distribution ◽  
Solar Chromosphere ◽  
Image Brightness ◽  
Observational Material ◽  
Birefringent Filter ◽  
Doppler Shifts

As observational material in this work we used spectroheliograms taken with the Crimean solar tower telescope in K232 and Hα filtergrams taken with the chromospheric telescope in Simeis. The Hα birefringent filter was so adjusted, that by tuning the last polaroid we could take filtergrams in the centre of Hα or combined filtergrams in the two wings at Hα ± 0·5 Å. So the effect of Doppler shifts on image-brightness distribution was diminished. We compared the brightness distribution with that of spectroheliograms.

scholarly journals Temporal and Spatial Fluctuations in Widths of solar Euv Lines

1980 ◽  
Vol 51 ◽  
pp. 53-53
Author(s):  
R.G. Athay ◽  
O.R. White
Keyword(s):  
Line Width ◽  
Sound Speed ◽  
Large Scale ◽  
Small Cells ◽  
The Sun ◽  
Doppler Shifts ◽  
Spatial Fluctuations ◽  
Local Sound ◽  
Line Widths ◽  
Temporal And Spatial

AbstractAnalyses of some 300 hours of time sequences of solar EUV line profiles obtained with 0S0-8 show large fluctuations in line widths. At a given location on the sun, line widths fluctuate temporally on time scales ranging from less than a minute to over an hour. At any given time, line widths fluctuate spatially on a variety of scales ranging from active region size to arc second size. Temporal and spatial fluctuations are of approximately the same amplitude. Thus, the sun can be characterized by an aggregate of small cells in each of which line widths are fluctuating in time and which have random phases with respect to each other.Spatial fluctuations in line width are correlated with large scale spatial fluctuations in brightness for some lines but not for others. Temporal fluctuations in width are sometimes correlated with either Doppler shifts or intensity fluctuations, but more often such correlations are absent.For a given line, the line width varies through an extreme range of about a factor of two. Nonthermal components of line width vary from approximately the local sound speed to a small fraction of the sound speed.

scholarly journals Reappraising Transition Region Line Widths in Light of Recent Alfvén Wave Discoveries

2008 ◽  
Vol 673 (2) ◽  
pp. L219-L223 ◽  
Author(s):  
Scott W. McIntosh ◽  
Bart De Pontieu ◽  
Theodore D. Tarbell
Keyword(s):  
Transition Region ◽  
Alfven Wave ◽  
Line Widths ◽  
Region Line

scholarly journals Experiment to Determine the Temperature Structure in the Solar Chromosphere and Corona

1972 ◽  
Vol 14 ◽  
pp. 668-669
Author(s):  
C. R. Negus
Keyword(s):  
Transition Region ◽  
Extreme Ultraviolet ◽  
Normal Incidence ◽  
Research Unit ◽  
Emission Lines ◽  
Solar Chromosphere ◽  
Temperature Structure ◽  
Ultraviolet Emission ◽  
Ionization Temperature ◽  
Intensity Ratios

An experiment is in course of preparation at the Astrophysics Research Unit at Culham for flight on a Sun-pointing rocket. It is designed to determine the ionization temperature and electron density as a function of height in the temperature range of about 8 × 104 K to 3 × 106 K by measuring limb to disk intensity ratios of extreme ultraviolet emission lines in the 170 to 850 Å region. The work is an extension of current experiments in which normal-incidence spectrographs are used to determine the structure lower in the chromosphere-corona transition region.

K emission-line widths and the solar chromosphere

Solar Physics ◽  
1971 ◽  
Vol 17 (2) ◽  
pp. 316-330 ◽  
Author(s):  
M. K. V. Bappu ◽  
K. R. Sivaraman
Keyword(s):  
Emission Line ◽  
Solar Chromosphere ◽  
Line Widths
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