Line-of-sight velocities observed in the inner solar corona during the total solar eclipses of 1980 and 1983

Raju, K. P.; Desai, J. N.; Chandrasekhar, T.; Ashok, N. M.

doi:10.1093/mnras/263.3.789

Cited by 15 publications

(12 citation statements)

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“…Spectroscopic observations give information about the physical state of the corona and also provide constraints on theories of coronal heating and solar wind acceleration. The line-of-sight Doppler velocities obtained from such observations now point out the existence of a dynamic corona (Chandrasekhar et al 1991 ;Raju et al 1993 ;Brekke et al 1997). Another important quantity is the nonthermal velocity, which is thought to be an indicator of the coronal heating mechanism (Harra-Murnion et al 1999).…”

Section: Introductionmentioning

confidence: 97%

The Physical Conditions in a Polar Coronal Hole and Nearby Regions from Norikura andSOHOObservations

Raju¹,

Sakurai²,

Ichimoto³

et al. 2000

ApJ

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The distribution of emission-line intensities, Doppler velocities, and line widths in a polar coronal hole and nearby regions are obtained from the spectroscopic observations carried out on 1998 November 3 at the Norikura Solar Observatory, Japan. The coronal red line [Fe X] j6374 that is prominent at coronal hole temperatures is used for the study. The coronal images in Fe IX and Fe X 171 and Fe XII 195 Ó Ó from the Extreme-Ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO) are used to get the temperature map of the corona at the time of observation. Combining both, we have obtained the nonthermal velocities in the region without the usual assumption of a uniform ion temperature. Several plume structures are identiÐed within the coronal hole, and it is found that line widths are smaller in plumes than in the interplume regions, which is also reported from recent SOHO observations. The line-of-sight Doppler velocities in the coronal hole are larger than those in the quiet region, probably because of the excess outÑow in the coronal hole. A rough negative correlation between intensity and Doppler velocity, similar to that between intensity and line width, is observed in the coronal hole. The typical nonthermal velocity in coronal holes is 24 km s~1 while that in quiet regions is 15 km s~1. The enhanced nonthermal velocity in the coronal hole is suggestive of the important role of the nonthermal broadening mechanism in the acceleration of fast solar wind. Also, the nonthermal velocities are larger (up to 27%) at the interplume regions as compared to plumes. The Ðndings generally support the prevailing view that the interplume regions are the source regions of the fast solar wind.

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Section: Introductionmentioning

confidence: 97%

The Physical Conditions in a Polar Coronal Hole and Nearby Regions from Norikura andSOHOObservations

Raju¹,

Sakurai²,

Ichimoto³

et al. 2000

ApJ

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“…For the 1965 eclipse the magnitudes of V ls range from 5 to 35 km s −1 in 73% of all cases while for the 1968 eclipse the V ls are less than 35 km s −1 only in 43% of all cases. In 1980and 1983, Raju et al [1993 also obtained appreciable velocities. We have confirmed these results at the eclipses of 1981 and 1999 [Delone et al, 2002a[Delone et al, , 2003a.…”

Section: Directed Motions: Methods For Velocity Determinationmentioning

confidence: 85%

Turbulent and directed mass motions in various structures of the low corona

Delone¹,

Yakunina²,

Porfir'eva³

et al. 2007

Int. J. Geomagn. Aeron.

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A brief review on turbulent and ordered plasma motions in the solar corona is presented. Velocities in quiet coronal regions, coronal loops, coronal holes, and cavities around quiescent prominences are analyzed. Data based on interferometric observations of several total solar eclipses obtained earlier by the authors and in addition the values of turbulent velocities resulting from revising the 5303 line profiles were used. Published data based both on ground and space observations in visual and far ultraviolet (UV) spectral region are collected. The turbulent velocities in quiet loop structures and diffuse quiet corona seem to be similar, and the coronal plasma in the vicinity of the quiet protuberances is less turbulent than in the quiet corona or in the coronal holes. Velocities of directed motions for different structures in the corona are examined. It seems that the turbulent velocities are comparable by their magnitudes with the direct plasma velocities; however, at the same time they are slightly less.

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“…Mass motions in the corona has been reported by Makarova (1969, 1975); Delone, Makarova, and Yakunina (1988) and Chandrasekhar et al (1991). The presence of the multiple components with excess blueshifts was reported by Raju et al (1993). Brynildsen, Kjeldseth-Moe, and Maltby (1995) mention the increasing fraction of redshifts in the transition region.…”

Section: Introductionmentioning

confidence: 79%

“…Then the radial scans from the fringe center were made to obtain the line profiles. The wavelength is calibrated as in Raju et al (1993). In order to reduce the noise, a 2x2 pixel averaging was done at the outset.…”

Section: Analysis and Data Reductionmentioning

confidence: 99%

Characteristics of the Solar Coronal Line Profiles from Fabry–Perot Interferometric Observations

2019

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This article reports the analysis of a set of Fabry-Perot interferograms that were studied to probe the physical parameters of the inner solar corona. The observations were carried out in the coronal green line, Fe XIV 5302.86Å, during the total solar eclipse of 21 June 2001 which occurred in Lusaka, Zambia. The study was performed in the radial range of 1.1-1.5 R ⊙ and examines the Doppler velocity, halfwidth, centroid and asymmetry and their correlations with each other at various points in the corona. It is found that 59 % of the line profiles are blueshifted, 34 % of them are single components and only 7 % of them are redshifted. The variations of halfwidth and Doppler velocity with respect to coronal height have a large scatter and shows no significant changes. It has been found that the variations of halfwidth with Doppler velocity or centroid follow a parabolic trend with a weak correlation, whereas the relation between halfwidth and the asymmetry is inconclusive. These results may provide more insight to the coronal dynamics and help in understanding the coronal physical problems.

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Line-of-sight velocities observed in the inner solar corona during the total solar eclipses of 1980 and 1983

Cited by 15 publications

References 0 publications

The Physical Conditions in a Polar Coronal Hole and Nearby Regions from Norikura andSOHOObservations

The Physical Conditions in a Polar Coronal Hole and Nearby Regions from Norikura andSOHOObservations

Turbulent and directed mass motions in various structures of the low corona

Characteristics of the Solar Coronal Line Profiles from Fabry–Perot Interferometric Observations

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