L. Teriaca, D. Banerjee and J. G. Doyle
Armagh Observatory, Armagh, BT61 9DG, N. Ireland
We study the variation of the line width and electron density as a function of height above the north polar coronal hole from forbidden spectral lines of Si VIII. The spectra were obtained with the Solar Ultraviolet Measurement of Emitted Radiation spectrometer flown on the Solar and Heliospheric Observatory spacecraft.The present data show that the non-thermal velocity increases from at 27 arcsec above the limb to some 250 arcsec ( 180,000 km) above the limb. The electron density shows a decrease from to over the same distance. This data implies that the non-thermal velocity is inversely proportional to the quadratic root of the electron density, in excellent agreement with that predicted for undamped radially propagating Alfvén waves. We show that the energy flux associated with these hydromagnetic waves is sufficient to drive the high velocity solar wind streams.