Search Publications
Evolution of magnetic field fluctuations in high-speed solar wind streams: Ulysses and Helios observations
Balogh, A.; Horbury, T. S.
Ulysses magnetic field measurements in high-speed streams emanating from the Sun's polar coronal holes reveal a complex combination of fluctuations on different scales. Measurements of the wavenumber dependence of radial and latitudinal power scaling, spectral index, and anisotropy of undisturbed polar magnetic field fluctuations between 1.4 and 4…
Ion cyclotron diffusion of velocity distributions in the extended solar corona
Cranmer, Steven R.
The Ultraviolet Coronagraph Spectrometer aboard the Solar and Heliospheric Observatory has revealed strong kinetic anisotropies and extremely large perpendicular temperatures of heavy ions in the extended solar corona. These observations have revived interest in the idea that the high-speed solar wind is heated and accelerated by the dissipation o…
Eruption and acceleration of flare-associated coronal mass ejection loops in the low corona
Plunkett, S. P.; Thompson, B. J.; Gurman, J. B. +1 more
Observations made by the EUV imaging telescope (EIT) and the Large-Angle Spectrometric Coronagraph (LASCO) on board the Solar Heliospheric Observatory (SOHO) have been used to characterize the eruption and acceleration of flare-associated coronal mass ejections (CMEs) in the low corona. For three well-observed limb events we tracked CME loops back…
Modulation of Jovian and galactic electrons in the heliosphere: 2. Radial transport of a few MeV electrons
Fichtner, H.; Ferreira, S. E. S.; Potgieter, M. S. +3 more
Previously, the latitudinal transport of ~7 MeV electrons was studied by comparing the results of a newly developed three-dimensional model, based on the numerical solution of Parker's transport equation including the Jovian source, with Ulysses observations. Here, the radial transport of ~16 MeV electrons is studied by comparing the model results…
A new model of solar EUV irradiance variability: 1. Model formulation
Mariska, J. T.; Warren, H. P.; Lean, J.
We present a new model of solar irradiance variability at extreme ultraviolet wavelengths (EUV, 50-1200 Å). In this model, quiet Sun, coronal hole, and active region intensities for optically thin emission lines are computed from emission measure distributions determined from spectrally and spatially resolved observations. For optically thick emis…
Validating the solar EUV proxy, E10.7
Tobiska, W. Kent
A demonstration of the improvement in thermospheric densities using the daily E10.7 proxy compared to F10.7 is shown. The daily altitude decay for the Solar Mesosphere Explorer (SME) satellite from April 1, 1982 through August 9, 1983, using both proxies and the actual altitude data, are compared. The F10.7 case fi…
Distribution of magnetic field components in the solar wind plasma
Matthaeus, W. H.; Smith, C. W.; Padhye, N. S.
We examine the probability distribution functions (PDFs) of fluctuations of magnetic field components using the Ulysses and Omnitape data sets to evaluate departures from Gaussian distributions. Functional fits as well as moment comparisons (kurtoses) are used in drawing conclusions concerning the degree of non-Gaussianity. Short-timescale fluctua…
Electromagnetic heavy ion cyclotron instability: Anisotropy constraint in the solar corona
Gary, S. Peter; Ofman, Leon; Winske, Dan +1 more
The electromagnetic proton cyclotron anisotropy instability is driven by T⊥p/T∥p>1 where p represents protons and the directional subscripts denote directions relative to the background magnetic field. Fluctuating field growth leads to wave-particle scattering, which in turn imposes an upper bound on the anisotropy of the …
Emission profiles of neutral oxygen and sulfur in Io's exospheric corona
Feldman, P. D.; Moos, H. W.; Strobel, D. F. +4 more
Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) observations of Io acquired in 1997 [Roesler et al., 1999] provided the first simultaneous spatially resolved measurements of emission from neutral sulfur and oxygen, the dominant atomic species in Io's exospheric corona. Previous measurements of Io's corona relied primarily …
Processes associated with particle transport in corotating interaction regions and near stream interfaces
Horbury, T. S.; Forsyth, R. J.; Kunow, H. +5 more
Pioneer and Ulysses observations of energetic particles and solar wind plasma and magnetic fields are analyzed to study particle transport in corotating interaction regions (CIRs) and near stream interfaces (SIs). Energetic particle diffusion with a lowered coefficient near the SIs as compared with the free solar wind may account for the energetic…