Search Publications
Heliospheric evolution of solar wind small-scale magnetic flux ropes
Moldwin, M. B.; Cartwright, M. L.
We present results from the first comprehensive small-scale flux rope survey between 0.3 and 5.5 AU using the Helios 1, Helios 2, IMP 8, Wind, ACE, and Ulysses spacecrafts to examine their occurrence rate, properties, and evolution. Small-scale flux ropes are similar to magnetic clouds and can be modeled as a constant-alpha, force-free, cylindrica…
Evolution of the spectrum of solar wind velocity fluctuations from 0.3 to 5 AU
Roberts, D. Aaron
Recent work has shown that at 1 AU from the Sun, the power spectrum of the solar wind magnetic field has the -5/3 spectral slope expected for Kolmogorov turbulence but that the velocity has closer to a -3/2 spectrum. This paper traces the changes in solar wind velocity spectra from 0.3 to 5 AU using data from the Helios and Ulysses spacecraft to s…
Cosmic ray diffusion tensor throughout the heliosphere
Matthaeus, W. H.; Bieber, J. W.; Burger, R. A. +3 more
We calculate the cosmic ray diffusion tensor based on a recently developed model of magnetohydrodynamic (MHD) turbulence in the expanding solar wind. Parameters of this MHD model are tuned by using published observations from Helios, Voyager 2, and Ulysses. We present solutions of two turbulence parameter sets and derive the characteristics of the…
North-south asymmetry of the location of the heliospheric current sheet revisited
Balogh, A.; ErdőS, G.
The possible latitudinal offset of the location of the heliospheric current sheet (HCS) is an important question, since it has impact on the understanding of various phenomena including the solar dynamo and the modulation of cosmic rays. In the declining phase of the previous, 22nd solar cycle, in 1993, a southward displacement of the HCS by 10° w…
Asymmetry of solar polar fields and the southward shift of HCS observed by Ulysses
Mursula, K.; Virtanen, I. I.
We study the hemispheric asymmetry of high-latitude unipolar fields and the latitudinal shift of the heliospheric current sheet (HCS) using Ulysses magnetic field observations during the perihelion passes in 1994-1995, 2001-2002, and 2007. Using the cumulative flux density and the best fit lines to its high-latitude observations in the two hemisph…
Pickup hydrogen distributions in the solar wind at ∼11 AU: Do we understand pickup ions in the outer heliosphere?
McComas, D. J.; Schwadron, N. A.; Elliott, H. A.
This study examines the detailed distribution of interstellar pickup hydrogen ions measured by the Surface Wave Process Program instrument on the New Horizons spacecraft en route to Pluto. The observations cover an 8 h interval on 15 October 2008 when the craft was at ∼11.3 AU, constituting the first detailed pickup ion measurements in the outer h…
Observation of the multifractal spectrum in solar wind turbulence by Ulysses at high latitudes
Wawrzaszek, Anna; Macek, Wieslaw M.
The aim of our study is to examine the question of multifractal scaling properties of turbulence in the solar wind at high latitudes. We analyze time series of the velocities of the solar wind during solar minimum (1994-1997, 2006-2007) at various heliographic latitudes measured in situ by Ulysses, which is the only mission that has investigated p…
Modeling anomalous cosmic ray oxygen gradients over successive solar cycles
Potgieter, M. S.; Strauss, R. D.
Cosmic ray drift directions depend both on the charge of the particle population under consideration, as well as the heliospheric magnetic field polarity which oscillates within a ∼22 year cycle. The differences in the cosmic ray drift patterns between successive solar cycles manifest themselves in the sign of the latitudinal cosmic ray gradient. …
On the relationship between coronal heating, magnetic flux, and the density of the solar wind
McComas, D. J.; Schwadron, N. A.; Riley, Pete +3 more
The stark differences between the current solar minimum and the previous one offer a unique opportunity to develop new constraints on mechanisms for heating and acceleration of the solar wind. We have used a combination of numerical simulations and analysis of remote solar and in situ observations to infer that the coronal heating rate, H, scales …
Propagation of Jovian electron jets in heliospheric flux tube structures
Heber, B.; Kopp, A.; Dunzlaff, P.
We discuss the propagation of magnetic flux tubes of solar origin through the heliosphere up to the orbit of Jupiter and the possibility that Jovian electron jets result from the interaction of these flux tubes with the magnetosphere of Jupiter. In order to do so, we analyze Ulysses observations in the interplanetary medium along the spacecraft's …