In a recent work, Landi & Cranmer (2009) measured the ion temperatures fromb the line widths of many ions observed by SUMER in a polar coronal hole. The measurements were done as a function of distance from the limb in the 1.02-1.17 solar radii range. Their study aimed at characterizing the region of acceleration of the fast solar wind by measuring the presence and effectiveness of the ion-cyclotron waves in accelerating the solar wind. They were looking for
a relation between ion temperatures and charge-to-mass ratio Z/A as a signature of ion-cyclotron wave action. They found that ion temperatures did depend on the Z/A ratio, but in a different way than predicted by models; at high Z/A values the ion temperature showed an upturn that could be explained by no theoretical model; these results were the same at all heights, meaining that ion cyclotron waves, if present, were active already at 0.02 solar radii from the photosphere. Landi & Cranmer (2009) used a sit'n'stare SUMER full spectrum observation, but many of the lines they used were weak and noisy, so they could only reach up to 1.17 solar radii, and also they could not relate their measurements to either polar plume or inter-plume plasma.
We propose to carry out joint deep exposure SUMER/EIS/UVCS observations of a polar coronal hole in order to measure ion temperatures versus Z/A, improving over Landi & Cranmer 2009 by carrying out measurements
1) for many more ions
2) for a larger height range
3) for a 60"x512" or (if possible) 120"x512" section of a coronal hole
4) linking the results to coronal hole structures on the disk
5) linking the results to UVCS ion temperatures at 1.9 solar radii. |
|