Search Publications
Radial evolution of nonthermal electron populations in the low-latitude solar wind: Helios, Cluster, and Ulysses Observations
Maksimovic, Milan; Štverák, Štěpán; Marsch, Eckart +3 more
We have performed a statistical study of a substantial amount of solar wind electron velocity distribution functions (eVDFs). In our data set, we combine measurements acquired onboard three spacecrafts (Helios, Cluster II, and Ulysses) in the low ecliptic latitudes covering the heliocentric distance from 0.3 up to 4 AU. In this study, we focus on …
Dependence of Solar-Wind Power Spectra on the Direction of the Local Mean Magnetic Field
Podesta, J. J.
Wavelet analysis can be used to measure the power spectrum of solar-wind fluctuations along a line in any direction (θ, phi) with respect to the local mean magnetic field B 0. This technique is applied to study solar-wind turbulence in high-speed streams in the ecliptic plane near solar minimum using magnetic field measurements with a c…
Empirical Constraints on Proton and Electron Heating in the Fast Solar Wind
Cranmer, Steven R.; Kasper, Justin C.; Matthaeus, William H. +1 more
We analyze measured proton and electron temperatures in the high-speed solar wind in order to calculate the separate rates of heat deposition for protons and electrons. When comparing with other regions of the heliosphere, the fast solar wind has the lowest density and the least frequent Coulomb collisions. This makes the fast wind an optimal test…
Bulk properties of the slow and fast solar wind and interplanetary coronal mass ejections measured by Ulysses: Three polar orbits of observations
McComas, D. J.; Forsyth, R. J.; Gosling, J. T. +2 more
We examined plasma and magnetic field observations from all three Ulysses polar orbits of the Sun to study the properties of the slow and fast solar wind and interplanetary coronal mass ejections (ICMEs). We derived equations to characterize the radial and latitudinal variations for these three types of heliospheric plasma and identify distinguish…
Electron and proton heating by solar wind turbulence
Cranmer, S. R.; Matthaeus, W. H.; Kasper, J. C. +2 more
Previous formulations of heating and transport associated with strong magnetohydrodynamic (MHD) turbulence are generalized to incorporate separate internal energy equations for electrons and protons. Electron heat conduction is included. Energy is supplied by turbulent heating that affects both electrons and protons and is exchanged between them v…
Scaling Laws of Turbulence and Heating of Fast Solar Wind: The Role of Density Fluctuations
Bruno, R.; Carbone, V.; Sorriso-Valvo, L. +2 more
Incompressible and isotropic magnetohydrodynamic turbulence in plasmas can be described by an exact relation for the energy flux through the scales. This Yaglom-like scaling law has been recently observed in the solar wind above the solar poles observed by the Ulysses spacecraft, where the turbulence is in an Alfvénic state. An analogous phenomeno…
Quiescent current sheets in the solar wind and origins of slow wind
Ko, Y. -K.; Moore, R. L.; von Steiger, R. +1 more
Solar wind near the heliospheric current sheet is investigated using Ulysses and ACE data in a superposed epoch analysis for several days on either side of the current sheets. Only data near sunspot minima are used, minimizing the influence of transients. New results are shown for composition and ionization state. Existing results showing a ∼2 day…
Modulation of Galactic Cosmic Ray Protons and Electrons During an Unusual Solar Minimum
Fichtner, H.; Scherer, K.; Ferreira, S. E. S. +5 more
During the latest Ulysses out-of-ecliptic orbit the solar wind density, pressure, and magnetic field strength have been the lowest ever observed in the history of space exploration. Since cosmic ray particles respond to the heliospheric magnetic field in the expanding solar wind and its turbulence, the weak heliospheric magnetic field as well as t…
Neutral H Density at the Termination Shock: A Consolidation of Recent Results
Möbius, E.; Bzowski, M.; Gloeckler, G. +2 more
We discuss a consolidation of determinations of the density of neutral interstellar H at the nose of the termination shock carried out with the use of various data sets, techniques, and modeling approaches. In particular, we focus on the determination of this density based on observations of H pickup ions on Ulysses during its aphelion passage thr…
Ion and electron superdiffusive transport in the interplanetary space
Zimbardo, Gaetano; Perri, Silvia
We study the propagation of energetic particles, accelerated by interplanetary shock waves, upstream of the shock. By using the appropriate propagator, we show that in the case of superdiffusive transport, the time profile of particles accelerated at a traveling planar shock is a power-law with slope 0<γ<1, at variance with the exponential p…