Bulk properties of the slow and fast solar wind and interplanetary coronal mass ejections measured by Ulysses: Three polar orbits of observations

• Published in: Journal of Geophysical Research - Space Physics Vol. 114; no. A1; pp. A01109 - n/a
• Main Authors: Ebert, R. W., McComas, D. J., Elliott, H. A., Forsyth, R. J., Gosling, J. T.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Geophysical Union 01-01-2009; Blackwell Publishing Ltd
• Subjects: Coronal mass ejections; Earth sciences; Earth, ocean, space; Ejecta, driver gases, and magnetic clouds; Exact sciences and technology; interplanetary coronal mass ejections; Interplanetary magnetic fields; Interplanetary Physics; Solar cycle variations; solar wind; Solar wind plasma; interplanetary coronal mass ejections; solar cycle variations; solar wind; Plasma; magnetic field; Coronal mass ejection; Minimum solar activity; Orbit; strength; Latitudinal variation; Proton temperature; Latitudinal gradient; latitude; variability; Sun; Proton density; Heliosphere; currents; Coronal hole; warming; solar cycles; protons; spatial variations; reduction; flow; Dynamic pressure
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/2008JA013631

We examined plasma and magnetic field observations from all three Ulysses polar orbits of the Sun to study the properties of the slow and fast solar wind and interplanetary coronal mass ejections (ICMEs). We derived equations to characterize the radial and latitudinal variations for these three types of heliospheric plasma and identify distinguishing features in their spatial variations. Most notably, the slow‐wind proton temperature falls less rapidly with distance than does the fast wind, indicating a source of enhanced heating in the low‐speed wind. After removing the radial variations from the measurements, only minor latitudinal gradients were identified. The fast wind has now been shown to be only weakly dependent on solar latitude for two successive solar minima. The spatial variations in the ICME properties do not differ significantly from the slow and fast solar wind, although the variability in their parameters is much larger. We also investigated solar cycle variations in the fast polar coronal hole (PCH) flows by comparing their properties measured over Ulysses' 1st and 3rd orbits. While the latitudinal gradients were similar, slight differences were observed in the radial dependence for the proton density and magnetic field strength. Also, a slight reduction in the proton speed at 1 AU, along with more significant decreases in the proton temperature, density, dynamic pressure, and magnetic field strength, was observed for the 3rd orbit relative to that for the 1st. These results are consistent with recent observations of weaker PCH flows for the current solar minimum.