Clues to the mode of excitation of Fe x ions in the solar corona from the 1980 eclipse observations

Singh, Jagdev

doi:10.1007/bf00152403

Cited by 13 publications

(3 citation statements)

References 6 publications

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“…The height variation of the nonthermal velocity in the inner corona (1.0È1.2 was reported by Singh (1985) and Hassler R _ ) et al (1990). The emission-line width increases with height and becomes constant at the height of 1.1È1.2…”

Section: Appendix a Nonthermal Velocities Through Transition Region Tsupporting

confidence: 55%

Microscopic Nonthermal Plasma Motions of Coronal Loops in a Solar Active Region

Hara¹,

Ichimoto²

1999

ApJ

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We present a spectroscopic observation of a solar active region NOAA 7590 with a coronagraph at the Norikura Solar Observatory, which provides high-resolution spectra of the visible coronal emission lines (Fe X j6374, Fe XIV j5303, Ca XV j5694) with a spatial sampling of Nonthermal veloci-2A .0 ] 2A .3. ties (m) estimated from Fe X j6374, Fe XIV j5303, and Ca XV j5694 in this observation are 14È20, 10È18, and 16È26 km s~1, respectively. The Ðrst two results are consistent with the results obtained by Cheng et al. and others. Even in the Ca XV structures the present observation does not conÐrm the large nonthermal velocity of 40È60 km s~1 to be typical value. The hypothesis that the nonthermal width in coronal emission lines is due to coronal waves is tested by carefully examining the relationship Alfve n between the width of coronal emission lines and orientation of coronal loops to the line-of-sight direction. From the comparison between edge-on loops in which the direction of magnetic Ðeld is nearly parallel to the line-of-sight direction and face-on loops in which the magnetic Ðeld is almost perpendicular to the line-of-sight direction, the full width at half-maximum (FWHM) of coronal emission lines for the edge-on loop appears to become smaller near the loop top than that for the face-on loops. The obvious decrease of FWHM of 0.04È0.07 (*m \ 3È5 km s~1) is found in the Fe XIV edge-on loops. A Although this may be evidence for the waves in coronal loops, the velocity amplitude seems to be Alfve n too small to explain all the nonthermal velocity reported so far.

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Section: Appendix a Nonthermal Velocities Through Transition Region Tsupporting

confidence: 55%

Microscopic Nonthermal Plasma Motions of Coronal Loops in a Solar Active Region

Hara¹,

Ichimoto²

1999

ApJ

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“…Emission profiles from forbidden transitions of Fe xiv (530.3 nm) and Fe x (637.6 nm) contain information on physical parameters such as temperature, mass motion, and turbulence. Coronal emission lines at visible wavelengths have been observed using Fabry-Perot (FP) techniques or spectrographs during total solar eclipses and with coronagraphs at high altitudes (e.g., Singh 1985;Ichimoto et al 1995;Hara and Ichimoto 1999). This kind of observation is constrained by scattering effects in the terrestrial atmosphere and rarely goes up to 1.5 R ⊙ (Singh et al 2006).…”

Section: Introductionmentioning

confidence: 99%

“…Below 1.2 R ⊙ the mode of excitation of Fe x 637.4 nm line is predominantly collisional. Both collisional and radiative excitation (from the photospheric continuum radiation) are important for 1.2R ⊙ < R < 1.3R ⊙ , whereas radiative excitation becomes dominant beyond R=1.3, 1.4R ⊙ (Singh 1985, Raju & Singh 1987. For Fe xiv the dominant excitation mechanism is collisional in the inner coronal regions (up to ≈ 1.4 R ⊙ ) (Raju et al 1991).…”

Section: Introductionmentioning

confidence: 99%