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Dammasch, I. E.; Hassler, D. M.; Curdt, W.; Wilhelm, K.

doi:10.1023/a:1005103224223

Cited by 56 publications

(89 citation statements)

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“…This indicates that although the intensity decreases inside coronal holes, the spatial fluctuations of the intensity are not decreasing proportionately. This agrees with previous studies (Lemaire et al 1997;Dammasch et al 1999;Pauluhn et al 2000;Stucki et al 2000a;Gallagher et al 1998). …”

Section: Distribution Of Intensitiessupporting

confidence: 93%

“…More recently, the distribution of intensities within transition region images using SOHO has been investigated by several authors (e.g. Lemaire et al 1997;Dammasch et al 1999;Pauluhn et al 2000;Stucki et al 2000a, with the SUMER spectrograph; Gallagher et al 1998, with the CDS spectrograph). The new observations confirm older results, but also reveal new insights.…”

Section: Distribution Of Intensitiesmentioning

confidence: 99%

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Properties of ultraviolet lines observed with the Coronal Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun

Stucki

Solanki

Pike

et al. 2002

A&A

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Abstract.We present an analysis of 14 ultraviolet emission lines belonging to different atoms and ions observed inside polar coronal holes and in the normal quiet Sun. The observations were made with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SOHO). This study extends previous investigations made with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer to higher temperatures. We compare line intensities, shifts and widths in coronal holes with the corresponding values obtained in the quiet Sun. While all lines formed at temperatures above 7 × 10 5 K show clearly the presence of the hole in their intensities, differences in line width are more subtle, with cooler lines being broader in coronal holes, while hotter lines tend to be narrower. According to the present data all lines are blueshifted inside the coronal hole compared to the normal quiet Sun. Almost all the lines formed between 80 000 K and 600 000 K (i.e. transition-region lines) show a correlation between blueshifts and brightness within coronal holes. This is in agreement with the conclusion reached by Hassler et al. (1999) that the fast solar wind emanates from the network and supports our previous study (Stucki et al. 2000b). For coronal lines, this trend seems to be reversed.

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Section: Distribution Of Intensitiessupporting

confidence: 93%

Section: Distribution Of Intensitiesmentioning

confidence: 99%

Properties of ultraviolet lines observed with the Coronal Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun

Stucki

Solanki

Pike

et al. 2002

A&A

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“…The widths of the distribution functions vary with the formation temperature and have a maximum near 1×10 5 K. Dammasch et al (1999c) found in addition that the shift and width distributions of the Si II, C IV and Ne VIII lines are also of Gaussian shape. Dere et al (1984Dere et al ( , 1987) deduced a sub-resolution structure of the transition region from HRTS observations on Spacelab 2 (≈1 angular resolution) with a filamentary configuration and a low filling factor.…”

Section: The Spatial Structurementioning

confidence: 78%

“…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. Peter and Judge (1999) and Dammasch et al (1999aDammasch et al ( , 1999d, on the other hand, came to the conclusion that the high-temperature lines are shifted towards blue in quiet-Sun areas (indicating outflows), and that the rest wavelengths of these lines have to be revised (cf., Sect. 9.1 of Part I).…”

Section: Plasma Flowsmentioning

confidence: 99%

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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“…The spectral center of the line profile was at every spatial pixel derived by using the centroid method (Dammasch et al 1999). Artificial effects of slit tilt and the orbital variation in the spatial distribution of the spectral center were removed before deriving the Dopplershift distribution.…”

Section: Data Calibration and Alignmentmentioning

confidence: 99%

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

He¹,

Marsch²,

Tu³

et al. 2010

A&A

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Context. It has already been established that the solar wind may originate at the edges of active regions (ARs), but the key questions of how frequently these outflows occur, and at which height the nascent solar wind originates have not yet been addressed. Aims. We study the occurrence rate of these intermittent outflows, the related plasma activities beneath in the low solar atmosphere, and the interplanetary counterparts of the nascent solar wind outflow. Methods. We use the observations from XRT/Hinode and TRACE to study the outflow patterns. The occurrence frequency of the intermittent outflow is estimated by counting the occurrences of propagating intensity enhancements in height-time diagrams. We adopt observations of SOT/Hinode and EIS/Hinode to investigate the phenomena in the chromosphere associated with the coronal outflows. The ACE plasma and field in-situ measurements near Earth are used to study the interplanetary manifestations. Results. We find that in one elongated coronal emission structure, referred to as strand, the plasma flows outward intermittently, about every 20 min. The flow speed sometimes exceeds 200 km s −1 , which is indicative of rapid acceleration, and thus exceeds the coronal sound speed at low altitudes. The inferred flow speed of the soft-X-ray-emitting plasma component seems a little higher than that of the Fe ix/x-emitting plasma component. Chromospheric jets are found to occur at the root of the strand. Upflows in the chromosphere are also confirmed by blue-shifts of the He ii line. The heliospheric plasma counterpart close to the Earth is found to be an intermediate-speed solar wind stream. The AR edge may also deliver some plasmas to a fraction of the fast solar wind stream, most of which emanate from the neighboring CH. Conclusions. The possible origin of the nascent solar wind in the chromosphere, the observed excessive outflow speed of over 200 km s −1 in the lower corona, and the corresponding intermediate-speed solar wind stream in interplanetary space are all linked in our case study. These phenomena from the low solar atmosphere to the heliosphere near Earth in combination shed new light on the solar wind formation process. These observational results will constrain future modeling of the solar winds originating close to an AR.

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Cited by 56 publications

References 0 publications

Properties of ultraviolet lines observed with the Coronal Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun

Properties of ultraviolet lines observed with the Coronal Diagnostic Spectrometer (CDS/SOHO) in coronal holes and the quiet Sun

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

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

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