Spectroscopic Studies of the Solar Corona. IV. Physical Properties of Coronal Structure

Singh, Jagdev; Ichimoto, Kiyoshi; Sakurai, Takashi; Muneer, S.

doi:10.1086/346000

Cited by 26 publications

(33 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first interesting result concerns the agreement we see with the Tsubaki (1975) photographic results, and, to some extent, with the Singh et al (1999Singh et al ( , 2002Singh et al ( , 2003 results (see Fig. 6), taking into account that these authors studied the line profiles in specific regions, at low latitudes and for a rather limited extension in height.…”

Section: Discussion Of Resultssupporting

confidence: 83%

“…We did not report all the analysed data (see Table 1), in order to keep a good enough signal-to-noise ratio, which means that very low level emissions are not discussed here. The fitting of line profiles and the computation of their FWHM has been well described by Tsubaki (1975) and recently by Kim (2000) and again by the Singh et al (1999Singh et al ( , 2002Singh et al ( , 2003, such that we do not consider it useful to repeat or duplicate here this part. The same is true for the extraction of the Doppler temperature, T D, and of the turbulent velocities, V t , making the assumption that the full profile is due to the superposition of thermal velocities at the formation temperature of Fe XIV, T i , and to unresolved turbulent and isotropic velocities V t , (also called non-thermal velocities), smearing the profiles integrated along each line of sight.…”

Section: Results Of the Analysismentioning

confidence: 98%

“…Recently, Singh et al (1999Singh et al ( , 2002Singh et al ( , 2003 published a series of new and well-documented papers devoted to the analysis of the main coronal lines observed using the Norikura Observatory Lyot coronagraph of 25-cm aperture. CCD spectra were obtained with high signal-to-noise ratio and the behaviour of the line broadening as a function of height was studied in particular.…”

Section: S Koutchmy Et Al: Analysis Of Non-thermal Velocities In Thmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of non-thermal velocities in the solar corona

Contesse¹,

Koutchmy²,

Viladrich³

2004

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. We describe new ground-based spectroscopic observations made using a 40-cm aperture coronagraph over a whole range of radial distances (up to heights of 12 above the limb) and along four different heliocentric directions N, E, S and W. The analysis is limited to the study of the brightest forbidden emission line of Fe XIV at 530.3 nm, in order to reach the best possible signal-to-noise ratio. To make the results statistically more significant, the extracted parameters are averaged over the whole length of the slit, and measurements are repeated fives times at each position; the corresponding dispersions in the results obtained along the slit are given. Central line profile intensities and full line widths (FWHM) are plotted and compared to measurements published by other authors closer to the limb. We found widths and turbulent (non-thermal) velocities of significantly higher values above the polar regions, especially when a coronal hole is present along the line of sight. We do not see a definitely decreasing behaviour of widths and turbulent velocities in equatorial directions for larger radial distances, as reported in the literature, although lower values are measured compared to the values in polar regions. The variation in the high corona is rather flat and a correlation diagram indicates that it is different for different regions and different radial distances. This seems to be the first analysis of the profiles of this coronal line, up to large heights above the limb for both equatorial and polar regions.

show abstract

Section: Discussion Of Resultssupporting

confidence: 83%

Section: Results Of the Analysismentioning

confidence: 98%

Section: S Koutchmy Et Al: Analysis Of Non-thermal Velocities In Thmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of non-thermal velocities in the solar corona

Contesse¹,

Koutchmy²,

Viladrich³

2004

Ann. Geophys.

View full text Add to dashboard Cite

show abstract

“…We also study the variation in the intensity ratio and the FWHM of these two and of other observed coronal emission lines to determine the variation in temperature with height above the limb. (Singh et al 1999(Singh et al , 2003a(Singh et al , 2003b. We mounted two CCD cameras on the coudé spectrograph in order to make observations in two emission lines simultaneously.…”

Section: Introductionmentioning

confidence: 99%

Complex Variations in the Line-Intensity Ratio of Coronal Emission Lines with Height above the Limb

Singh

Sakurai

Ichimoto

et al. 2004

ApJ

Self Cite

View full text Add to dashboard Cite

We obtained spectroscopic observations simultaneously in pairs of coronal emission lines, one line being [Fe x] l6374 and the other line being [Fe xi] l7892, [Fe xiii] l10747, or [Fe xiv] l5303, and we studied the variations in the intensity and FWHM ratios of these lines with respect to those of 6374 as a function of height above the A limb. We find that the intensity ratio of the 7892 and 10747 line with respect to the 6374 line increases withÅ A height and that the intensity ratio of 5303 to 6374 decreases with height above the limb. This implies that theÅ A temperature in coronal loops will appear to increase with height if we consider the intensity ratio of 7892 to A 6374 a negligible variation in temperature in the case of the 10747 and 6374 line pair, while the temperatureÅ A will appear to decrease with height if we consider the intensity ratio of 5303 to 6374 . The normalized FWHMÅ A (with respect to wavelength) ratio of 6374 to all the other coronal lines observed increases with height. The A FWHM ratio at the limb depends on the pair of emission lines chosen; it is about 1 in the case of the 6374 and 7892 emission lines, indicating a common temperature and nonthermal velocity in the coronal loops near the A limb, and it is about 0.7 at the limb in the case of the 6374 and 5303 lines and becomes about 1 at a height of A 120Љ. The varying FWHM ratios with height indicate that hotter and colder plasmas in coronal loops mix with each other. Therefore, the observed increase in the FWHM of coronal emission lines, which are associated with plasma at about 1 MK with height, may not be due to an increase in nonthermal motions caused by coronal waves but may be due to an interaction with relatively hotter plasma.

show abstract

“…The SUMER observations indicate even less line-width variations with height in the more active corona. Singh et al (2003) found height variations of line profiles in the visible light that depended on the formation temperatures of the lines. So, the solar conditions appear to have a direct influence on the line-width variations with height.…”

Section: Discussionmentioning

confidence: 95%