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02.12.1; 02.12.3; 06.01.2; 06.01.3; 06.03.2; 06.19.2

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

Received date, accepted date


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