Ion temperatures as observed in a solar coronal hole

From the widths of the extreme ultraviolet (EW) lines measured by the SUMER instrument on SOHO, it was found previously (Tu et al. 1998) that the aver age temperature of Ne+7, at heights (relative to ho) above the southern sol ar limb from 17 " to 64 ", ranges between 1.3 and 5x10(6) K and of Ne+6 bet ween 1 and 4x10(6) K. For mass-per-charge numbers greater than 4 the temper atures of the ions increase slightly with increasing mass-per-charge, while the thermal speed reveals no clear trend. We present a new data set with e xposure times much longer than the ones in the previous study. The results obtained from line width analysis of Fe XII (1242 Angstrom), Mg X (1249 Ang strom), Mg VIII (772 Angstrom) Ne VIII (770 Angstrom), and Si VIII (1445 An gstrom) support our previous study. In this case, the trend of increasing t emperature begins at a mass-per-charge number of 3. A qualitative explanati on based on ion-cyclotron-resonance heating within linear kinetic theory is suggested.