Search Publications
The solar wind composition throughout the solar cycle: A continuum of dynamic states
Zurbuchen, T. H.; Gloeckler, G.; Fisk, L. A. +1 more
Variations in the speed and elemental and ionic charge composition of the solar wind are reported throughout the solar cycle, as observed by the SWICS instrument on Ulysses. The apparent bimodal nature of the solar wind during the solar minimum does not persist throughout the solar cycle. Rather, with increasing solar activity, a continuum of sola…
Ulysses' second fast-latitude scan: Complexity near solar maximum and the reformation of polar coronal holes
Balogh, A.; Reisenfeld, D. B.; McComas, D. J. +5 more
Ulysses' second fast latitude scan, near solar maximum, comprises a complicated mixture of solar wind flows from a variety of sources at high southern as well as low heliolatitudes. In contrast, observations northward of ~40° N show the reformation of relatively steady fast solar wind flows, which are virtually indistinguishable from the polar cor…
Phase-steepened Alfvén waves, proton perpendicular energization and the creation of magnetic holes and magnetic decreases: The ponderomotive force
Lakhina, G. S.; Tsurutani, B. T.; Goldstein, B. E. +6 more
Solar wind protons detected within Magnetic Holes (MHs) and Magnetic Decreases (MDs) are found to be preferentially heated perpendicular to B0. The MHs/MDs are associated with the phase-steepened edges of nonlinear Alfvén waves. The proton anisotropies can lead to the proton cyclotron and mirror mode plasma instabilities. We examine the…
Relationship between discontinuities, magnetic holes, magnetic decreases, and nonlinear Alfvén waves: Ulysses observations over the solar poles
Balogh, A.; Lakhina, G. S.; Tsurutani, B. T. +6 more
Ulysses magnetic field data are used to study magnetic field microstructure over the solar poles. Magnetic holes (MHs) and magnetic decreases (MDs) are found to be located at the phase-steepened edges of nonlinear Alfvén waves. The phase-steepened edges (directional discontinuities) occur in time-coincidence with MHs, one edge of an MD, or through…
Solar wind from high-latitude coronal holes at solar maximum
McComas, D. J.; Elliott, H. A.; von Steiger, R.
In this study we combine Ulysses' observations from the solar wind plasma (SWOOPS) and ion composition (SWICS) instruments to study high-latitude coronal holes near solar maximum for the first time. While chromospheric and coronal composition signatures indicate that there is a unique type of solar wind, which flows from coronal holes, variations …
The draping of heliospheric magnetic fields upstream of coronal mass ejecta
Balogh, A.; Jones, G. H.; Forsyth, R. J. +1 more
The propagation of a fast coronal mass ejection through the interplanetary medium results in compression and draping of existing heliospheric magnetic fields, forming an upstream sheath. Such sheaths are a common context for planar magnetic structures, where the magnetic field is ordered into laminar sheets. A technique is presented to estimate th…
Strongly underwound magnetic fields in co-rotating rarefaction regions: Observations and Implications
Smith, E. J.; Schwadron, N. A.; Murphy, N.
Observations of the magnetic field orientation in co-rotating rarefaction regions (CRRs) reveals that the field can be significantly more radial than predicted by the Parker model. In particular, CRRs sampled by the Ulysses spacecraft beyond 4 AU from the sun often show average field orientations deviating by more than 30° from the expected Archim…
Relation between Pressure Balance Structures and polar plumes from Ulysses high latitude observations
Sakurai, Takashi; Suess, Steven T.; Yamauchi, Yohei
Ulysses observations have shown that pressure balance structures (PBSs) are a common feature in high-latitude, fast solar wind near solar minimum. Previous studies of Ulysses/SWOOPS plasma data suggest these PBSs may be remnants of coronal polar plumes. Here we find support for this suggestion in an analysis of PBS magnetic structure. We used Ulys…
Cosmic electron gradients in the inner heliosphere
Heber, Bernd; Clem, John; Evenson, Paul
We report the first determination of the radial gradient of cosmic ray electrons in the inner heliosphere at rigidities of 1.2 and 2.5 GV from 1 to 5 AU. Since this determination was made during the A+ solar polarity state, it also constitutes the only determination for particles in a polarity state opposite to their charge sign. We fin…
Composition measurements above the Southern Solar Polar Region around the solar activity maximum by the Ulysses COSPIN/LET instrument
Sanderson, T. R.; Marsden, R. G.; Tranquille, C. +1 more
In November 2000, during the second southern polar passage (SPP), the Ulysses spacecraft reached its highest heliographic latitude (80.2°) at a solar radial distance of ~2.27 AU. The first SPP in 1994 took place as the level of solar activity was approaching the minimum between the cycles 22 and 23. The recent high-latitude observations during the…