Ion Temperatures as Observed in a Solar Coronal Hole |
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Authors: | C-Y Tu E Marsch K Wilhelm |
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Institution: | (1) Max-Planck-Institut für Aeronomie, D-37191 Katlenburg-Lindau, Germany |
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Abstract: | From the widths of the extreme ultraviolet (EUV) lines measured by the SUMER instrument on SOHO, it was found previously (Tu et al. 1998) that the average temperature of Ne+7, at heights (relative to h0) above the southern solar limb from 17″ to 64″, ranges between 1.3 and 5 × 106 K and of Ne+6 between 1 and 4 × 106 K. For mass-per-charge numbers greater than 4 the temperatures 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 exposure times much longer than the ones in the previous study. The results obtained from line width analysis of Fe XII (1242 Å), Mg X (1249 Å), Mg VIII (772 Å) Ne VIII (770 Å), and Si VIII (1445 Å) support our previous study. In this case, the trend of increasing temperature begins at a mass-per-charge number of 3. A qualitative explanation based on ion-cyclotron-resonance heating within linear kinetic theory is suggested. |
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