Variation of polar coronal hole profiles with solar cycle

We compared the H I Ly alpha polar coronal hole profiles obtained during th e three Spartan 201 flights (in 1993, 1994, and 1995) and during the more r ecent UVCS/SOHO mission. We found that at 2.1 R. there are no significant v ariations of the line shape over the several years of the descending phase of the solar cycle. However, there may be some evidence for the 1.8 R. prof iles being broader towards solar minimum. The profiles at 2.1 R. are differ ent from profiles obtained at 1.8 R.; they have clearly narrower cores and wide wings. We fitted the profiles with single and/or multiple Gaussian fun ctions and calculated their typical 1/e half widths.