Solar Wind Velocity and Anisotropic Coronal Kinetic Temperature Measured with the O Vi Doublet Ratio

Doppler dimming of the Ovi resonance lines (l1032Aa, l1037Aa) in an expanding corona is calculated including the pumping effect on the Ovi l1037.61 Aa of both Cii lines at l1036.34Aa and l1037.02Aa, and the effect of the width of the absorption profiles of the coronal oxygen ions along the incident...

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Bibliographic Details
Published in:Solar physics 1998-11, Vol.183 (1), p.77-90
Main Authors: Dodero, MA, Antonucci, E, Giordano, S, Martin, R
Format: Article
Language:English
Subjects:
Absorbing
Absorption
Anisotropy
Astronomy
Diagnostic systems
Emissivity
Incident radiation
Ions
Magnetic fields
Oxygen
Oxygen ions
Solar physics
Solar wind velocity
Velocity distribution
Wind speed
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Summary:Doppler dimming of the Ovi resonance lines (l1032Aa, l1037Aa) in an expanding corona is calculated including the pumping effect on the Ovi l1037.61 Aa of both Cii lines at l1036.34Aa and l1037.02Aa, and the effect of the width of the absorption profiles of the coronal oxygen ions along the incident radiation. The pumping effect of the Cii line at l1036.34Aa allows us to extend to approximately 450kms-1 the measurement of solar wind velocities with the Ovi line ratio technique. Since the emissivity ratio of the Ovi doublet depends on the width of the oxygen coronal absorbing profiles, this ratio can provide an accurate measurement of the solar wind velocity in the case that the width of the absorbing profile along the direction of the incident radiation is independently determined. However, if on the one hand the ratio of the emissivities of the Ovi doublet has limitations in probing the wind velocity, on the other hand it can be used as a diagnostics for inferring the velocity distribution of the coronal Ovi ions along the radial, and detecting possible velocity anisotropies. This diagnostics, applied to recent observational results, allows us to infer that the velocity distribution of the oxygen ions is much broader in the direction perpendicular to the magnetic field direction, and that the acceleration of the fast solar wind in the first 2 solar radii is high.
ISSN:0038-0938
1573-093X
DOI:10.1023/A:1005007429583