Search Publications
Magnetic Helicity Spectrum of Solar Wind Fluctuations as a Function of the Angle with Respect to the Local Mean Magnetic Field
Podesta, J. J.; Gary, S. P.
Magnetic field data acquired by the Ulysses spacecraft in high-speed streams over the poles of the Sun are used to investigate the normalized magnetic helicity spectrum σ m as a function of the angle θ between the local mean magnetic field and the flow direction of the solar wind. This spectrum provides important information about the …
Solar Wind Modeling with Turbulence Transport and Heating
Matthaeus, William H.; Goldstein, Melvyn L.; Usmanov, Arcadi V. +1 more
We have developed an axisymmetric steady-state solar wind model that describes properties of the large-scale solar wind, interplanetary magnetic field, and turbulence throughout the heliosphere from 0.3 AU to 100 AU. The model is based on numerical solutions of large-scale Reynolds-averaged magnetohydrodynamic equations coupled with a set of small…
Model of the Jovian magnetic field topology constrained by the Io auroral emissions
Bonfond, B.; Zarka, P.; Grodent, D. +1 more
The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins alo…
Detailed Fit of "Critical Balance" Theory to Solar Wind Turbulence Measurements
Wicks, Robert T.; Horbury, Timothy S.; Forman, Miriam A.
We derive the reduced spectrum of turbulent magnetic fluctuations at different frequencies f which would be observed by a single spacecraft in the solar wind when the magnetic field was at an angle θ B to the solar wind flow, if the wavevector spectrum in the solar wind frame were in anisotropic "critical balance" (CB) as proposed by Go…
The distribution of solar wind speeds during solar minimum: Calibration for numerical solar wind modeling constraints on the source of the slow solar wind
Arge, C. N.; Odstrcil, D.; Owens, M. J. +2 more
It took the solar polar passage of Ulysses in the early 1990s to establish the global structure of the solar wind speed during solar minimum. However, it remains unclear if the solar wind is composed of two distinct populations of solar wind from different sources (e.g., closed loops which open up to produce the slow solar wind) or if the fast and…
Effect of Current Sheets on the Solar Wind Magnetic Field Power Spectrum from the Ulysses Observation: From Kraichnan to Kolmogorov Scaling
Li, G.; Hu, Q.; Qin, G. +1 more
The MHD turbulence theory developed by Iroshnikov and Kraichnan predicts a k-1.5 power spectrum. Solar wind observations, however, often show a k-5/3 Kolmogorov scaling. Based on 3 years worth of Ulysses magnetic field data where over 28 000 current sheets are identified, we propose that the current sheet is the cause of the …
Comparison of Observations at ACE and Ulysses with Enlil Model Results: Stream Interaction Regions During Carrington Rotations 2016 - 2018
Luhmann, J. G.; Russell, C. T.; Jian, L. K. +6 more
During the latitudinal alignment in 2004, ACE and Ulysses encountered two stream interaction regions (SIRs) each Carrington rotation from 2016 to 2018, at 1 and 5.4 AU, respectively. More SIR-driven shocks were observed at 5.4 AU than at 1 AU. Three small SIRs at 1 AU merged to form a strong SIR at 5.4 AU. We compare the Enlil model results with s…
Scale Dependence of Magnetic Helicity in the Solar Wind
Brandenburg, Axel; Balogh, André; Subramanian, Kandaswamy +1 more
We determine the magnetic helicity, along with the magnetic energy, at high latitudes using data from the Ulysses mission. The data set spans the time period from 1993 to 1996. The basic assumption of the analysis is that the solar wind is homogeneous. Because the solar wind speed is high, we follow the approach first pioneered by Matthaeus et al.…
Latitudinal and radial gradients of galactic cosmic ray protons in the inner heliosphere - PAMELA and Ulysses observations
Gieseler, J.; Heber, B.; Picozza, P. +5 more
Ulysses, launched on 6 October 1990, was placed in an elliptical, high inclined (80.2°) orbit around the Sun, and was switched off in June 2009. It has been the only spacecraft exploring high-latitude regions of the inner heliosphere. The Kiel Electron Telescope (KET) aboard Ulysses measures electrons from 3 MeV to a few GeV and protons and helium…
Current sheets from Ulysses observation
Li, G.; Miao, B.; Peng, B.
Current sheet is a significant source of solar wind MHD turbulence intermittency. It has long been recognized that these structures can arise from non-linear interactions of MHD turbulence. Alternatively, they may also be relic structures in the solar wind that have a solar origin, e.g., magnetic walls of flux tubes that separate solar wind plasma…