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J.G Doyle

Coronal Hole Diagnostics out to $8R_{\odot}$

J.G. Doyle, L. Teriaca - D. Banerjee

Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
emails: jgd@star.arm.ac.uk, lte@star.arm.ac.uk, dipu@star.arm.ac.uk

Received date, accepted date

Abstract:

The Si VIII line width measurements and Ne estimates based on SUMER observations are combined with LASCO and UVCS output to provide an overview of its variations with height above a polar coronal hole. From the combined dataset we find a radial dependence of the electron density, in the range 1-2 $R_{\odot}$ as r-8, from 2 to 4 $R_{\odot}$ as r-4 and then as r-2. Combining the Si VIII half width at 1/e of the peak intensity with the UVCS O VI half width, we find a small increase of the half width from 1 to 1.2 $R_{\odot}$, then a plateau until 1.5 $R_{\odot}$, thereafter a sharp increase until 2 $R_{\odot}$, finally a more gradual increase reaching 550 km s-1 at 3.5 $R_{\odot}$. Our data suggests that the MHD waves responsible for the excess line broadening tends to become non-linear as it reaches 1.2 $R_{\odot}$.

Sun: Corona -Ultraviolet; SOHO-Sun: waves; Sun: Coronal Hole; Sun: Electron Density





Aileen Brannigan
1999-06-02