Search Publications
Reducing heliospheric magnetic flux from coronal mass ejections without disconnection
Crooker, N. U.; Gosling, J. T.; Kahler, S. W.
Until 1995, disconnection at the Sun was thought to be the only solution to the problem of balancing the magnetic flux coronal mass ejections (CMEs) added to the heliosphere, in spite of the fact that the expected solar wind signature of disconnection was rare. Disconnection was pictured as merging between open field lines to create completely dis…
Sources of the solar wind at solar activity maximum
Smith, E. J.; Neugebauer, M.; Zurbuchen, T. H. +2 more
The photospheric sources of solar wind observed by the Ulysses and ACE spacecraft from 1998 to early 2001 are determined through a two-step mapping process. Solar wind speed measured at the spacecraft is used in a ballistic model to determine a foot point on a source surface at a solar distance of 2.5 solar radii. A potential-field source-surface …
Modeling the heliospheric current sheet: Solar cycle variations
Riley, Pete; Linker, J. A.; Mikić, Z.
In this report we employ an empirically driven, three-dimensional MHD model to explore the evolution of the heliospheric current sheet (HCS) during the course of the solar cycle. We compare our results with a simpler ``constant-speed'' approach for mapping the HCS outward into the solar wind to demonstrate that dynamic effects can substantially de…
On the origin of radial magnetic fields in the heliosphere
Gosling, J. T.; Skoug, R. M.
Numerous examples of events wherein the heliospheric magnetic field (HMF) measured at a fixed point in space remains nearly radial for many hours have been reported in the literature. Such events are observed both in the normal solar wind and within disturbances driven by coronal mass ejections (CMEs). A very large fraction of these extended, near…
The underlying direction of the heliospheric magnetic field through the Ulysses first orbit
Balogh, A.; Forsyth, R. J.; Smith, E. J.
Between February 1992 and April 1998 the Ulysses spacecraft carried out the first survey of how the properties of the solar wind and heliospheric magnetic field vary with latitude during the declining and minimum phases of the solar cycle. In this paper we report on how the underlying direction of the heliospheric magnetic field varied through the…
Signatures of wave-ion interactions in the solar wind: Ulysses observations
Goldstein, Bruce E.; Neugebauer, Marcia; Gary, S. Peter
Theory and simulations predict that resonant wave-particle scattering by enhanced magnetic fluctuations yields characteristic signatures in properties of solar wind ions. Here Ulysses/Solar Wind Observations Over the Poles of the Sun (SWOOPS) instrument measurements of protons and alpha particles are examined to seek three types of these signature…
Ulysses Cosmic Ray and Solar Particle Investigation/Kiel Electron Telescope observations: Charge sign dependence and spatial gradients during the 1990-2000 A > 0 solar magnetic cycle
Kunow, H.; Wibberenz, G.; Ferreira, S. E. S. +10 more
Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in September 1997. From 1991 to mid-2000, solar polar magnetic field observations indicate a magnetic field pointing outward over the northern polar region (A > 0 epoch). While the first fast latitude scan in 1994/1995 was performed around solar minimum, the second Ulysse…
Low-latitude solar wind during the Fall 1998 SOHO-Ulysses quadrature
Biesecker, D. A.; Poletto, G.; Ko, Y. -K. +4 more
The Fall 1998 Solar and Heliospheric Observatory (SOHO)-Ulysses quadrature occurred when Ulysses was at 5.2 AU, 17.4°S of the equator, and off the west limb of the Sun. SOHO coronal observations, at heliocentric distances of a few solar radii, showed that the line through the solar center and Ulysses crossed, over the first days of observations, a…
Observation of decay phases of solar energetic particle events at 1 and 5 AU from the Sun
Balogh, A.; Dalla, S.; Heber, B. +2 more
The slow decay phase of gradual solar energetic particle (SEP) events has been interpreted as an indication of particle reservoirs being established in the inner heliosphere. The same phenomenon is sometimes termed spectral invariance and explained in terms of a magnetic bottle effect, whereby a barrier impedes particle escape. In alternative to t…
Alfvénic turbulence in high-latitude solar wind: Radial versus latitudinal variations
Bavassano, B.; Pietropaolo, E.; Bruno, R.
Plasma and magnetic field measurements by Ulysses during its first out-of-ecliptic orbit have allowed extensive investigations on the behavior of Alfvénic turbulence in high-latitude solar wind from 1 to 5 AU. Most analyses have shown that the turbulence evolution in high-latitude wind is radial, rather than latitudinal, in nature. However, a rece…