Polar coronal hole density and its solar wind consequences using LASCO observations

Knowledge of the electron density in various coronal structures and their gradients in the inner and outer corona form an integral part of our understanding of the solar wind phenomenon and the coronal heating processes (Guhathakurta & Fisher 1997, Ko et al. 1997, Fisher & Guhathakurta 1995, and Habbal et al. 1995). However, until recent joint observations of Spartan 201-03 white-light coronagraph, in conjunction with Ulysses in situ north polar coronal hole plasma parameters, (Guhathakurta & Fisher 1997 and Guhathakurta, Fisher & Neugebauer 1997) and radio ranging measurements (Guhathakurta, Fisher &: Woo 1997 and Guhathakurta, Woo, & Fisher 1997), electron density distribution was limited by the field of view of white-light coronagraphs (typically out to 6 R_⊙). Now, for the first time we have a series of white-light coronagraphs (SOHO/LASCO) whose combined field of view extends from 1.1 - 30 R_⊙ (Bruckner et al. 1995). In this paper we specifically determine the electron density of the north polar coronal hole using MkIII and LASCO C2 and C3 observations from 1.2 - 8.0 R_⊙. The electron density in the region 1-1.2 R_⊙ has been estimated by Fludra et al. 1997. We combine these numbers with the estimate from LASCO to obtain a density profile from 1-8 R_⊙. These results are then compared to the recent analysis of the Spartan 201-03 data and their implications for solar wind modeling discussed.