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We present a self-consistent empirical model for several plasma parameters of a polar coronal hole near solar minimum, derived from observations with the Solar and Heliospheric Observatory Ultraviolet Coronagraph Spectrometer. The model describes the radial distribution of density for electrons, H , and O and the outflow of O are also significantly larger than the corresponding velocities of H . We discuss the constraints and 5ϩ 0 implications on various theoretical models of coronal heating and acceleration.

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A peculiar young active region was observed in 1998 March with the Ultraviolet Coronagraph Spectrometer (UVCS) over the southwest limb. The spectra showed strong emission in the 974 line of fluorine-like iron, [Fe xviii], which is brightest at an electron temperature of 10 6.8 K, and lines of Ne ix, [Ca xiv], [Ca xv], Fe xvii, [Ni xiv], and [Ni xv]. It is the only active region so far observed to show such high temperatures 0.5 R above the solar limb. We derive the emission measure and estimate elemental abundances. The active region produced a number of coronal mass ejections (CMEs). After one CME on March 23, a bright post-CME arcade was seen in EIT and Yohkoh/SXT images. Between the arcade and the CME core, UVCS detected a very narrow, very hot feature, most prominently in the [Fe xviii] line. This feature seems to be the reconnection current sheet predicted by flux rope models of CMEs. Its thickness, luminosity, and duration seem to be consistent with the expectations of the flux rope models for CME. The elemental abundances in the bright feature are enhanced by a factor of 2 compared to those in the surrounding active region, i.e., a first ionization potential enhancement of 7-8 compared to the usual factor of 3-4.

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We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5R s , obtained during the Galileo solar conjunction in 1997 January, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scattered component of the oxygen 1032 and 1037.6 Å lines as measured with the ultraviolet coronagraph spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO). White light images of the corona from the large-angle spectroscopic coronagraph (LASCO) on SOHO taken simultaneously are used to place the Doppler radio scintillation and ultraviolet measurements in the context of coronal structures. These combined observations provide the first direct confirmation of the view recently proposed by Woo & Martin that the slow solar wind is associated with the axes, also known as stalks, of streamers. Furthermore, the ultraviolet observations also show how the fast solar wind is ubiquitous in the inner corona and that a velocity shear between the fast and slow solar wind develops along the streamer stalks.