The inner solar corona seen by SUMER, LASCO/C1, and EIT:
Electron densities and temperatures during the rise of the new solar cycle

Wilhelm, K.; Inhester, B.; Newmark, Jeffrey

doi:10.1051/0004-6361:20011608

Cited by 21 publications

(14 citation statements)

References 49 publications

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“…This is consistent with the findings that spectral lines formed at transitionregion temperature indicate high LOS velocities (≈20 km s −1 ) in prominences (Mein 1977;Wilhelm et al 2002a).…”

Section: Prominencessupporting

confidence: 92%

“…ChiuderiDrago et al (1977), and recently , concluded from UV and radio observations that hot and cold plasmas must coexist in coronal holes at low altitudes. The same conclusion was reached for quiet-Sun regions near the equator from VUV observations of lines with different formation temperatures (Wilhelm et al 2002a). A review by Feldman et al (2000a) summarizes recent observations and interpretations of the morphology of the solar atmosphere during the sunspot minimum.…”

Section: The Spatial Structuresupporting

confidence: 55%

“…The quiet equatorial corona at low altitudes is cooler (≈1 MK) than the corona at midlatitudes (≈1.5 MK) according to SUMER, EIT, and LASCO/C1 observations (Wilhelm et al 2002a). Near the equator high-density (n e ≈ 5 × 10 9 cm −3 ) transition-region plasma and low-density (n e ≈ 2 × 10 8 cm −3 ) coronal plasmas are present at the same height of 5 Mm.…”

Section: The Equatorial Corona Coronal Loops and The Slow Solar Windmentioning

confidence: 95%

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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: Prominencessupporting

confidence: 92%

Section: The Spatial Structuresupporting

confidence: 55%

Section: The Equatorial Corona Coronal Loops and The Slow Solar Windmentioning

confidence: 95%

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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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“…and T e ≥ 1.5 MK in 1998 (Wilhelm 1999c;Wilhelm et al 2002). The density is comparable to those deduced here for the lanes, but the temperature is much higher (cf.…”

Section: Discussionsupporting

confidence: 80%

Solar coronal-hole plasma densities and temperatures

Wilhelm¹

2006

A&A

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Polar plumes extending from the Sun into the solar corona have long been seen during eclipses, and can now be studied without this restriction with telescopes and spectrometers on board of spacecraft. Despite the large amount of observational data available on this prominent phenomenon, it is not clear whether plumes contribute substantially to the fast solar-wind streams emanating from coronal holes. An understanding of the processes leading to the formation of bright plumes and the surrounding darker inter-plume regions in coronal holes requires a good knowledge of the physical conditions in plumes and their environment. This investigation aims at measuring the electron densities and temperatures in these regions with the help of radiance ratios of ultraviolet emission lines obtained by SUMER on SOHO. It finds densities of about 7 × 10 7 cm −3 in bright plumes and 1.3 × 10 7 cm −3 in inter-plume lanes at ≈45 Mm above the limb. At this height, the total plume cross-section relative to the size of the coronal hole was found to be less than 8%. The densities drop by a factor of roughly two over the next 80 Mm in height, in lanes a little less than seen in plumes. In this height range, the electron temperatures in plumes are ≈7.5 × 10 5 K and ≈1.13 × 10 6 K in inter-plume regions. The effective ion temperatures, deduced from the line widths, are higher and nearly independent of the altitude in plumes, whereas they increase in inter-plume regions, starting from an even higher level. No systematic dependence of the line-of-sight bulk velocities on the brightness could be found in the coronal-hole plasma.

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“…For all the observed line ratios this translates into a possible error of no more than 20%, which is within the accuracy of the atomic data. An earlier paper by Wilhelm et al (2002) suggested blending of the O  759.43 Å line with a S  line at 759.34 Å.…”

Section: Resultsmentioning

confidence: 96%

Sunspot plume observations in the EUV

Doyle¹,

Madjarska

2003

A&A

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Abstract. The electron density over a bright sunspot plume region was evaluated using lines within the O  760 Å multiplet. The plume showed an intensity enhancement factor of ≈9 in the O  lines compared to regions outside the sunspot umbra. Internal agreement between the various ratios is excellent which would suggest that the O  lines do not suffer from blending problems.The derived mean electron densities for the sunspot plume is log N e /cm −3 ≈ 9.9 compared to log N e /cm −3 ≈ 10.20−10.45 in the surrounding area. The derived gas pressure in the plume compared to that outside leads weight to the suggestion that it is plasma flowing from outside the spot into the umbra at transition region temperatures that is the main cause of the down-flows. The plume non-thermal velocities are 5 to 10 km s −1 smaller than those measured in regions external to the spot, suggesting significantly less turbulence within the umbra.

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The inner solar corona seen by SUMER, LASCO/C1, and EIT: Electron densities and temperatures during the rise of the new solar cycle

Cited by 21 publications

References 49 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

Solar coronal-hole plasma densities and temperatures

Sunspot plume observations in the EUV

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