The relationship of solar abundance measurements to the electron temperature in a polar coronal hole

We discuss the behavior of the intensity of the Mg vr lambda 1191.64 spectr al line relative to the intensity of the Ne VI lambda 1005.78 spectral line as a function of height above the limb in the solar north polar coronal ho le. The intensities of Mg VI lines relative to Ne VI lines have been shown to be excellent indicators of element abundance variations due to the first ionization potential (FIP) effect. We find that the Mg VI/Ne VI intensity ratio increases with height above the limb by factors ranging from 1.7 to 4 over a height range extending from about 6 " above the limb to 28 " above the limb. We conclude that this intensity ratio increase is primarily due t o an increase of electron temperature with height, rather than the result o f an FIP effect, and therefore caution must be exercised in using any Mg VI /Ne vr line ratio as an abundance diagnostic above the limb in the polar ho les. At 6 " above the limb, the Mg VI/Ne vr line ratio indicates that the s olar Mg/Ne abundance ratio is probably within a factor of 2 of the photosph eric abundance ratio. The spectra we use were recorded by the Solar Ultravi olet Measurements of Emitted Radiation spectrometer on the Solar and Helios pheric Observatory spacecraft.