Temperature Dependence of Ultraviolet Line Average Doppler Shifts in the Quiet Sun

Chae, Jongchul; Yun, Hong Sik; Poland, A. I.

doi:10.1086/313064

Cited by 124 publications

(106 citation statements)

References 27 publications

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“…Yet, the measurement of the VUV lines emitted from plasma in the transition region and lower corona do not give a fully conclusive picture of the flow pattern there, because the shifts observed may be due to waves and/or directed flows, and the interpretation of the data is not entirely free from ambiguities. Chae et al (1998b) and Brekke et al (1997a) analysed Doppler shifts from many lines for the quiet Sun and over an electron temperature range of 10 4 K to 1 MK together with more recent evaluation by Dammasch et al (1999aDammasch et al ( , 1999b and Peter and Judge (1999). The results are compiled in Fig.…”

Section: Flow Speeds Near the Sunmentioning

confidence: 99%

“…Brekke et al (1997a), Warren et al (1997a), and Chae et al (1998b) continued the investigation of the average red shift with SUMER data. These studies confirmed a maximum red shift corresponding to more than 10 km s −1 near 2 × 10 5 K and provided evidence that downflows of about 5 km s −1 were present for Ne VIII at 77.0 nm and Mg X at 62.5 nm, assuming the standard laboratory wavelengths.…”

Section: Plasma Flowsmentioning

confidence: 99%

“…2.1.3.3), and is very close to the temperature with the highest nonthermal velocities red shift, downwards motion; negative: blue shift, upward motion) are plotted. They were taken from several sources Brekke 1993;Brekke et al 1997a;Chae et al 1998b;Peter and Judge 1999;Dammasch et al 1999a). The largest shifts occur in transition-region lines at temperatures between ≈1 × 10 5 K and 2 × 10 5 K. Note the change from a red to a blue shift above 6 × 10 5 K for more recent observations (cf., Sect.…”

Section: Plasma Flowsmentioning

confidence: 99%

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Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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In Part I of this review, the concepts of solar vacuum-ultraviolet (VUV) observations were outlined together with a discussion of the space instrumentation used for the investigations. A section on spectroradiometry provided some quantitative results on the solar VUV radiation without considering any details of the solar phenomena leading to the radiation. Here, in Part II, we present solar VUV observations over the last decades and their interpretations in terms of the plasma processes and the parameters of the solar atmosphere, with emphasis on the spatial and thermal structures of the chromosphere, transition region and corona of the quiet Sun. In addition, observations of active regions, solar flares and prominences are included as well as of small-scale events. Special sections are devoted to the elemental composition of the solar atmosphere and theoretical considerations on the heating of the corona and the generation of the solar wind.

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Section: Flow Speeds Near the Sunmentioning

confidence: 99%

Section: Plasma Flowsmentioning

confidence: 99%

Section: Plasma Flowsmentioning

confidence: 99%

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Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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“…The thermal line width is calculated using the formation temperature related to the temperature of the maximum abundance of the ions in the Mazzotta et al (1998) ionization equilibrium. Chae et al (1998b) has pointed out that for the lines used here, the temperature of the maximum abundance is not very different from the effective temperature of the formation of the ions. However, for some other ions, like Fe viii, these two kinds of temperature are distinct (Brooks et al 2011), but we do not use it in this work.…”

Section: Gaussian Fit To the Normalized Average Profilesmentioning

confidence: 81%

“…The method we use here is the cool-line method (Feldman et al 1982;Brekke et al 1997;Chae et al 1998b;Peter & Judge 1999;Davey et al 2006). These previous studies have illustrated that chromospheric lines have nearly no Doppler shift on average, so they can be used as reference lines to deduce the spectral dispersion of a spectral window by applying a linear fit between the wavelength pixels and rest wavelengths of them.…”

Section: Absolute Wavelength Calibration Using Reference Spectramentioning

confidence: 99%

Temperature dependence of ultraviolet line parameters in network and internetwork regions of the quiet Sun and coronal holes

Wang

McIntosh

Curdt

et al. 2013

A&A

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Aims. We study the temperature dependence of the average Doppler shift and the non-thermal line width in network and internetwork regions for both the quiet Sun (QS) and the coronal hole (CH), by using observations of the Solar Ultraviolet Measurements of Emitted Radiation instrument onboard the Solar and Heliospheric Observatory spacecraft. Methods. We obtain the average Doppler shift and non-thermal line width in the network regions of QS, internetwork regions of QS, network regions of CH, and internetwork regions of CH by applying a single-Gaussian fit to the line profiles averaged in each of the four regions. The formation temperatures of the lines we use cover the range from 10 4 to 1.2 × 10 6 K. Two simple scenarios are proposed to explain the temperature dependence of the line parameters in the network regions. In one of the scenarios, the spectral line consists of three components: a rapid, weak upflow generated in the lower atmosphere, a nearly static background, and a slow cooling downflow. In the other scenario, there are just two components, which include a bright core component and a faint wide tail one.Results. An enhancement of the Doppler shift magnitude and the non-thermal line width in network regions compared to the internetwork regions is reported. We also report that most transition region lines are less redshifted (by 0−8 km s −1 ) and broader (by 0−5 km s −1 ) in CH compared to the counterparts of QS. In internetwork regions, the difference in the Doppler shifts between the coronal hole and the QS is slightly smaller, especially for the lines with formation temperatures lower than 2 × 10 5 K. And the two simple scenarios can reproduce the variation in the line parameters with the temperature very well. Conclusions. Our results suggest that the physical processes in network and internetwork regions are different and that one needs to separate network and internetwork when discussing dynamics and physical properties of the solar atmosphere. The agreement between the results of the observation and our scenarios suggests that the temperature dependence of Doppler shifts and line widths might be caused by the different relative contributions of the three components at different temperatures. The results may shed new light on our understanding of the complex chromosphere-corona mass cycle. However, the existing observational results do not allow us to distinguish between the two scenarios. At this stage, a high-resolution instrument Interface Region Imaging Spectrograph is highly desirable.

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The Heating of the Solar Corona

Viall

Moortel

Downs

et al. 2021

Geophysical Monograph Series

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Temperature Dependence of Ultraviolet Line Average Doppler Shifts in the Quiet Sun

Cited by 124 publications

References 27 publications

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Temperature dependence of ultraviolet line parameters in network and internetwork regions of the quiet Sun and coronal holes

The Heating of the Solar Corona

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