New Measurements of the Winds of Uranus

Hammel, Heidi B.; Rages, K.; Lockwood, G. W.; Karkoschka, Erich; Pater, Imke de

doi:10.1006/icar.2001.6689

Cited by 76 publications

(67 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 456 rings, although clearly extended, are unresolved. Numerous bright features are visible on the disk of Uranus near the South Polar bright band and at high northern latitudes, as previously reported by Karkoschka (1998) and Hammel et al (2001). There are also features near the equator, at latitudes where such activity has never been detected before.…”

Section: Observationssupporting

confidence: 84%

Near-infrared adaptive optics imaging of the satellites and individual rings of Uranus

Gibbard¹,

Pater²,

Hammel³

2005

Icarus

View full text Add to dashboard Cite

We present the first Earth-based images of several of the individual faint rings of Uranus, as observed with the adaptive optics system on the W.M. Keck II telescope on four consecutive days in October 2003. We derive reflectivities based on multiple measurements of 8 minor moons of Uranus as well as Ariel and Miranda in filters centered at wavelengths of 1.25(J), 1.63(H), and 2.1(Kp) µm. These observations have a phase angle of 1.84 • -1.96 • . We find that the small satellites are somewhat less bright than in observations made by the HST at smaller phase angles, confirming an opposition surge effect. We calculate albedoes for the ring groups and for each ring separately. We find that the ring particles, as well as the particles in the three other ring groups, have albedoes near 0.043 at these phase angles. The equivalent depths of some of the individual rings are different than predicted based upon ring widths from occultation measurements (assuming a constant particle ring brightness); in particular the γ ring is fainter and the η ring brighter than expected. Our results indicate that q, the ratio of ring intensity at apoapse vs. periapse, is close to 3.2 ± 0.16. This agrees well with a model that has a filling factor for the ring of 0.06 (Karkoschka, 2001, Icarus 151, 78-83). We also determine values of the north to south brightness ratio for the individual rings and find that in most cases they are close to unity.

show abstract

Section: Observationssupporting

confidence: 84%

Near-infrared adaptive optics imaging of the satellites and individual rings of Uranus

Gibbard¹,

Pater²,

Hammel³

2005

Icarus

View full text Add to dashboard Cite

show abstract

“…Summarizing, let us emphasize that the existing opinion that the equatorial jets produced in barotropic simulations are always directed westward is fallacious although a certain preference to the formation of westward jets has been noticeable. Note also that the simulated equatorial jets are not necessarily symmetric with respect to the equator; this fact has been addressed in some discussions of the circulation on Uranus (Karkoschka, 1998;Hammel et al, 2001Hammel et al, , 2005Sromovsky and Fry, 2005).…”

Section: Equatorial Jetsmentioning

confidence: 97%

Anisotropic turbulence and zonal jets in rotating flows with a β-effect

Galperin

Sukoriansky

Dikovskaya

et al. 2006

Nonlin. Processes Geophys.

108

107

View full text Add to dashboard Cite

Abstract. Numerical studies of small-scale forced, twodimensional turbulent flows on the surface of a rotating sphere have revealed strong large-scale anisotropization that culminates in the emergence of quasi-steady sets of alternating zonal jets, or zonation. The kinetic energy spectrum of such flows also becomes strongly anisotropic. For the zonal modes, a steep spectral distribution, E(n)=C Z ( /R) 2 n −5 , is established, where C Z =O(1) is a non-dimensional coefficient, is the angular velocity, and R is the radius of the sphere, respectively. For other, non-zonal modes, the classical, Kolmogorov-Batchelor-Kraichnan, − 5 3 spectral law is preserved. This flow regime, referred to as a zonostrophic regime, appears to have wide applicability to large-scale planetary and terrestrial circulations as long as those are characterized by strong rotation, vertically stable stratification and small Burger numbers. The well-known manifestations of this regime are the banded disks of the outer planets of our Solar System. Relatively less known examples are systems of narrow, subsurface, alternating zonal jets throughout all major oceans discovered in state-of-the-art, eddy-permitting simulations of the general oceanic circulation. Furthermore, laboratory experiments recently conducted using the Coriolis turntable have basically confirmed that the lateral gradient of "planetary vorticity" (emulated via the topographic β-effect) is the primary cause of the zonation and that the latter is entwined with the development of the strongly anisotropic kinetic energy spectrum that tends to attain the same zonal and non-zonal distributions, −5 and − 5 3 , respectively, in both the slope and the magnitude, as the corresponding spectra in other environmental conditions. The non-dimensional coCorrespondence to: B. Galperin (bgalperin@marine.usf.edu) efficient C Z in the −5 spectral law appears to be invariant, C Z 0.5, in a variety of simulated and natural flows.This paper provides a brief review of the zonostrophic regime. The review includes the discussion of the physical nature, basic mechanisms, scaling laws and universality of this regime. A parameter range conducive to its establishment is identified, and collation of laboratory and naturally occurring flows is presented through which the zonostrophic regime manifests itself in the real world.

show abstract

“…Images were recorded at f/32 (0.02″/pixel plate scale) with three filters: J, H-continuum and CH 4 (long) ( Hammel et al (2001) we calculate that they would have appeared on the far side of Uranus during the earlier NIRI observation.…”

Section: Observationsmentioning

confidence: 99%