Ion distributions in large magnetic holes in the fast solar wind

Magnetic holes are isolated localized depressions in the magnitude of the i nterplanetary magnetic field. Six examples of long-duration (9 to 30 min) m agnetic holes observed by the Ulysses spacecraft at high heliographic latit udes near 3 AU are studied in detail. Each of the holes was in pressure bal ance with its surroundings. The proton-proton and alpha-proton differential streaming typically observed in the fast solar wind dropped to very low le vels within the holes. The ion temperatures perpendicular to the magnetic f ield also increased, leading to marginal mirror-mode stability. Possible ca uses of these high-latitude magnetic holes are discussed. A new method of d econvolving the three-dimensional angular distributions of the protons and alpha particles from the ion instrument's angular response is described in an appendix.