Search Publications
Least-squares gradient calculation from multi-point observations of scalar and vector fields: methodology and applications with Cluster in the plasmasphere
Dunlop, M. W.; de Keyser, J.; Décréau, P. M. E. +1 more
This paper describes a general-purpose algorithm for computing the gradients in space and time of a scalar field, a vector field, or a divergence-free vector field, from in situ measurements by one or more spacecraft. The algorithm provides total error estimates on the computed gradient, including the effects of measurement errors, the errors due …
The three-dimensional structure of Saturn's equatorial jet at cloud level
Hueso, R.; Sánchez-Lavega, A.; Pérez-Hoyos, S.
The three-dimensional structure of Saturn's intense equatorial jet from latitudes 8° N to 20° S is revealed from detailed measurements of the motions and spectral reflectivity of clouds at visible wavelengths on high resolution images obtained by the Cassini Imaging Science Subsystem (ISS) in 2004 and early 2005. Cloud speeds at two altitude level…
Prediction of the 1-AU arrival times of CME-associated interplanetary shocks: Evaluation of an empirical interplanetary shock propagation model
Cho, K. -S.; Kim, K. -H.; Moon, Y. -J.
The traveltimes of interplanetary (IP) shocks at 1 AU associated with coronal mass ejections (CMEs) can be predicted by the empirical shock arrival (ESA) model of Gopalswamy et al. [2004] based on a constant IP acceleration. We evaluate the ESA model using 91 IP shocks identified from sudden commencement (SC)/sudden impulse (SI) on the Earth and b…
Hubble Space Telescope and Optical Observations of Three Pulsating Accreting White Dwarfs in Cataclysmic Variables
Szkody, Paula; Sion, Edward M.; Solheim, Jan-Erik +8 more
Ultraviolet observations using the Solar Blind Channel on the Hubble Space Telescope provide light curves and low-resolution spectra of three pulsating white dwarfs in the cataclysmic variables SDSS J013132.39-090122.3, SDSS J161033.64-010223.3, and SDSS J220553.98+115553.7. The UV light curves show enhanced pulsation amplitudes over those from si…
The Three-Dimensional Morphology of VY Canis Majoris. II. Polarimetry and the Line-of-Sight Distribution of the Ejecta
Humphreys, Roberta M.; Helton, L. Andrew; Jones, Terry Jay +2 more
We use imaging polarimetry taken with the HST Advanced Camera for Surveys High Resolution Camera to explore the three-dimensional structure of the circumstellar dust distribution around the red supergiant VY Canis Majoris. The polarization vectors of the nebulosity surrounding VY CMa show a strong centrosymmetric pattern in all directions except d…
Dynamical Evidence for Environmental Evolution of Intermediate-Redshift Spiral Galaxies
Smith, Graham P.; Treu, Tommaso; Ellis, Richard S. +2 more
Combining resolved optical spectroscopy with panoramic HST imaging, we study the dynamical properties of spiral galaxies as a function of position across two intermediate-redshift clusters, and we compare the cluster population to field galaxies in the same redshift range. By modeling the observed rotation curves, we derive maximal rotation veloci…
Radiation in the atmosphere of Venus
Bullock, Mark A.; Crisp, David; Taylor, Fredric W. +3 more
This chapter reviews the observations of the radiative fluxes inside and outside the Venusian atmosphere, along with the available data about the planetary energy balance and the distribution of sources and sinks of radiative energy. We also briefly address the role of the heat budget on the atmospheric temperature structure, global circulation, t…
Time-Distance Imaging of Solar Far-Side Active Regions
Zhao, Junwei
It is of great importance to monitor large solar active regions on the far side of the Sun for space weather forecasting, in particular, to predict their appearance before they rotate into our view from the solar east limb. Local helioseismology techniques, including helioseismic holography and time distance, have successfully imaged solar far-sid…
Two-dimensional hybrid model of wave and beam heating of multi-ion solar wind plasma
ViñAs, A. F.; Ofman, L.
We study the heating and the acceleration of protons and heavy ions by waves in the solar wind, as well as the nonlinear influence of heavy ions on the wave structure, using a two-dimensional (2-D) hybrid model. Protons and heavy ions are treated kinetically by solving their equations of motion in the self-consistent electric and magnetic fields o…
Can the solar wind originate from a quiet Sun region?
Tu, C. -Y.; Marsch, E.; He, J. -S.
Context: It is well known that the fast solar wind originates from coronal holes (CHs). However, the question whether it can also originate from quiet Sun regions has not yet been answered.
Aims: To study this problem we analyze SOHO data obtained from observations made in a quiet Sun area. The data set includes far-ultraviolet data from SUMER…