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…
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…
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.…
Spectral Properties of Regions and Structures in the Interstellar Boundary Explorer (IBEX) Sky Maps
Reisenfeld, D. B.; McComas, D. J.; Schwadron, N. A. +5 more
We study the spectral properties of different regions and structures in the energetic neutral atom (ENA) maps at energies from ~0.5 keV to ~6 keV from the Interstellar Boundary Explorer (IBEX) mission. We find that (1) an ankle-shaped break (spectrum hardens) between ~1 keV and ~2 keV characterizes the polar spectra and the right flank, while a kn…
Possible Evidence for a Fisk-type Heliospheric Magnetic Field. I. Analyzing Ulysses/KET Electron Observations
Fichtner, H.; Scherer, K.; Ferreira, S. E. S. +6 more
The propagation of energetic charged particles in the heliospheric magnetic field is one of the fundamental problems in heliophysics. In particular, the structure of the heliospheric magnetic field remains an unsolved problem and is discussed as a controversial topic. The first successful analytic approach to the structure of the heliospheric magn…
Solar Cycle Variations in the Elemental Abundance of Helium and Fractionation of Iron in the Fast Solar Wind: Indicators of an Evolving Energetic Release of Mass from the Lower Solar Atmosphere
McIntosh, Scott W.; Kasper, Justin C.; Stevens, Michael L. +2 more
We present and discuss the strong correspondence between evolution of the emission length scale in the lower transition region and in situ measurements of the fast solar wind composition during the most recent solar minimum. We combine recent analyses demonstrating the variance in the (supergranular) network emission length scale measured by the S…
Measurement of Intermittency of Anisotropic Magnetohydrodynamic Turbulence in High-speed Solar Wind
Wu, D. J.; Yang, L.; Luo, Q. Y.
We investigate the intermittency of anisotropic magnetohydrodynamic (MHD) turbulence in high-speed solar wind. Using the data recorded by the Ulysses spacecraft, we apply the Castaing function to model the probability density functions of the fluctuating magnetic field and calculate the magnetic structure functions (SFs) Sp of the order…