The relation between the zonal jets and ammonia anomalies in Jupiter

2021 ◽  
Author(s):  
Nimrod Gavriel ◽  
Keren Duer ◽  
Eli Galanti ◽  
Yohai Kaspi ◽  
Keyword(s):  
Wind Profile ◽  
Ammonia Concentration ◽  
Equatorial Region ◽  
Meridional Gradient ◽  
Zonal Jets ◽  
Axis Of Rotation ◽  
Different Depths ◽  
Eddy Fluxes ◽  
Abundance Anomalies ◽  
Latitudinal Variations

<div> <div>Juno's six‐channel MWR measurements might reveal information about the structure of the wind profile below the cloud level. These measurements are used to calculate the nadir brightness temperature (T<sub>b</sub>), a profile determined by temperature and by the opacity of the atmosphere. This opacity for the relevant frequencies of the MWR is determined mostly by ammonia abundance. The T<sub>b</sub> vary considerably between the different channels (indicating on different depths) and between latitudes. Here, we take the <!-- mathfontold --> T<sub>b</sub> as an indicator for ammonia concentration and examine the relation to the zonal jets. We find that different theoretical mechanisms can explain this relation at different latitudes. At the equatorial region, the superrotation is accompanied by vertical upwelling. This vertical advection, driven by a convergence of eddy fluxes directed perpendicular to the axis of rotation, is shown to explain the equatorial ammonia enrichment. At the mid-latitudes, assuming that the ammonia is enriched with depth, alternating Ferrel-like cells framed by opposite vertical velocities redistributes the ammonia, maximizing its meridional gradient where the jet peaks. This hypothesis is well apparent in the data, using both correlation analysis and theoretical arguments. We find that dynamical reasoning, suggesting on vertical velocities through the cloud-level zonal jets, can explain the latitudinal variations in <!-- mathfontold --> T<sub>b,</sub> under the assumption that they are caused by ammonia abundance anomalies.</div> </div>

On the retrograde propagation of critical thermal convection in a slowly rotating spherical shell

2010 ◽  
Vol 659 ◽  
pp. 505-515 ◽  
Author(s):  
SHIN-ICHI TAKEHIRO
Keyword(s):  
Spherical Shell ◽  
Thermal Convection ◽  
Rotation Speed ◽  
Spherical Geometry ◽  
Radial Component ◽  
Equatorial Region ◽  
Propagation Mechanism ◽  
Budget Analysis ◽  
Axis Of Rotation ◽  
Vorticity Budget

The retrograde propagation mechanism of critical thermal convection with a sectorial pattern emerging in a slowly rotating spherical shell is investigated through vorticity budget analysis. In the equatorial region, stretching and shrinking of the fluid columns in the direction of the axis of rotation due to the radial component of velocity causes retrograde propagation, whereas in the mid-latitudes, tilting of the radial component of planetary vorticity by the radial shear of the latitudinal component of velocity is dominant. The switching of the propagating direction from retrograde to prograde according to the increase in the rotation speed of the shell originates from the transition of the morphology of vortices from the ‘banana-shaped’ type due to the constraint of the spherical geometry to the columnar type due to the Taylor–Proudman constraint. The variation of the morphology of vortices reverses the tendency of stretching/shrinking of fluid columns accompanied by their cylindrically radial displacement.

scholarly journals Dynamic Europa ocean shows transient Taylor columns and convection driven by ice melting and salinity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yosef Ashkenazy ◽  
Eli Tziperman
Keyword(s):  
Ocean Dynamics ◽  
Ice Thickness ◽  
Ice Melting ◽  
Extraterrestrial Life ◽  
Critical Elements ◽  
Zonal Jets ◽  
Axis Of Rotation ◽  
Ocean Salinity ◽  
Bottom Heating ◽  
Weak Stratification

AbstractThe deep (~100 km) ocean of Europa, Jupiter’s moon, covered by a thick icy shell, is one of the most probable places in the solar system to find extraterrestrial life. Yet, its ocean dynamics and its interaction with the ice cover have received little attention. Previous studies suggested that Europa’s ocean is turbulent using a global model and taking into account non-hydrostatic effects and the full Coriolis force. Here we add critical elements, including consistent top and bottom heating boundary conditions and the effects of icy shell melting and freezing on ocean salinity. We find weak stratification that is dominated by salinity variations. The ocean exhibits strong transient convection, eddies, and zonal jets. Transient motions organize in Taylor columns parallel to Europa’s axis of rotation, are static inside of the tangent cylinder and propagate equatorward outside the cylinder. The meridional oceanic heat transport is intense enough to result in a nearly uniform ice thickness, that is expected to be observable in future missions.

Europa's dynamic ocean: Taylor columns, eddies, convection, ice melting and salinity

2020 ◽  
Author(s):  
Yosef Ashkenazy ◽  
Eli Tziperman
Keyword(s):  
Boundary Conditions ◽  
Deep Ocean ◽  
Equatorial Region ◽  
Ocean Dynamics ◽  
Global Ocean ◽  
Ocean Bottom ◽  
Extraterrestrial Life ◽  
Zonal Jets ◽  
Ocean Salinity ◽  
Bottom Heating

<p class="p1">The deep ocean (~100 km) of Europa, Jupiter’s moon, is covered by a thick (tens of km) icy shell, and is one of the most probable places in the solar sys- tem to find extraterrestrial life. Yet, its ocean dynamics and its interaction with the ice cover have so far received little attention. Previous studies sug- gested that Europa’s ocean is turbulent, yet neglected to take into account the effects of ocean salinity and appropriate boundary conditions for the ocean’s temperature. Here, the ocean dynamics of Europa is studied using global ocean models that include non-hydrostatic effects, a full Coriolis force, con- sistent top and bottom heating boundary conditions, and including the effects of melting and freezing of ice on salinity. The density is found to be dominated by salinity effects and the ocean is very weakly stratified. The ocean exhibits strong transient vertical convection, eddies, low latitude zonal jets and Tay- lor columns parallel to Europa’s axis of rotation. In the equatorial region, the Taylor columns do not intersect the ocean bottom and propagate equatorward, while off the equator, the Taylor columns are static. The meridional oceanic heat transport is intense enough to result in a nearly uniform ice thickness, that is expected to be observable in future missions.</p>

scholarly journals Anisotropic Rotational and Isotropic Residual Isopycnal Mesoscale Eddy Fluxes

2010 ◽  
Vol 40 (11) ◽  
pp. 2511-2524 ◽  
Author(s):  
Carsten Eden
Keyword(s):  
Potential Energy ◽  
Baroclinic Instability ◽  
Mesoscale Eddy ◽  
Divergent Part ◽  
Eddy Flux ◽  
Zonal Jets ◽  
Eddy Fluxes ◽  
Ocean Models ◽  
Model Diagnosis ◽  
Classical Picture

Abstract In the generalized temporal residual mean (TRM-G) framework, the diapycnal rotational eddy fluxes are defined such that the residual divergent diapycnal eddy flux is related to irreversible changes of buoyancy, that is, diapycnal mixing (or temporal changes of variance and higher order moments) only. Here, it is discussed that for the isopycnal eddy fluxes a similar physically meaningful property exists: rotational isopycnal eddy fluxes can be defined in TRM-G such that the residual divergent part of the flux is related to removal of mean available potential energy and transfer to eddy energy only, that is, to the classical picture of eddy activity. In two idealized eddying models, both featuring strong mesoscale eddy-driven zonal jets, large isopycnal eddy fluxes are circulating at the flanks of the jets. The residual isopycnal eddy fluxes, however, are predominantly meridional and thus downgradient, indicating vanishing anisotropic mixing of isopycnal thickness, consistent with the classical picture of eddy-driven overturning by baroclinic instability in jets. Using isotropic thickness mixing—standard in ocean models—appears therefore as sufficient in this model diagnosis.

On Variations in the Chandler Frequency

1972 ◽  
Vol 1 ◽  
pp. 77-85
Author(s):  
H.J.M. Abraham ◽  
J.N. Boots
Keyword(s):  
Axis Of Rotation ◽  
The Earth ◽  
Actual Motion ◽  
Chandler Frequency

This paper suggests that some of the reported changes in the Chandler frequency are associated with inelastic changes in the Earth. There has been controversy as to how much of the apparent secular polar drift is due to actual motion of the axis of rotation within the Earth, and how much it is merely the reflection of movements by certain observatories. Therefore, when more southern data are available it will be interesting to see whether similar results are obtained.

Reference Coordinate System Requirements for Geophysics

1975 ◽  
Vol 26 ◽  
pp. 87-92
Author(s):  
P. L. Bender
Keyword(s):  
Coordinate System ◽  
Polar Motion ◽  
Main Part ◽  
Measurement Techniques ◽  
Reference Points ◽  
Angular Motion ◽  
Coordinate Systems ◽  
Axis Of Rotation ◽  
The Earth ◽  
Fixed System

AbstractFive important geodynamical quantities which are closely linked are: 1) motions of points on the Earth’s surface; 2)polar motion; 3) changes in UT1-UTC; 4) nutation; and 5) motion of the geocenter. For each of these we expect to achieve measurements in the near future which have an accuracy of 1 to 3 cm or 0.3 to 1 milliarcsec.From a metrological point of view, one can say simply: “Measure each quantity against whichever coordinate system you can make the most accurate measurements with respect to”. I believe that this statement should serve as a guiding principle for the recommendations of the colloquium. However, it also is important that the coordinate systems help to provide a clear separation between the different phenomena of interest, and correspond closely to the conceptual definitions in terms of which geophysicists think about the phenomena.In any discussion of angular motion in space, both a “body-fixed” system and a “space-fixed” system are used. Some relevant types of coordinate systems, reference directions, or reference points which have been considered are: 1) celestial systems based on optical star catalogs, distant galaxies, radio source catalogs, or the Moon and inner planets; 2) the Earth’s axis of rotation, which defines a line through the Earth as well as a celestial reference direction; 3) the geocenter; and 4) “quasi-Earth-fixed” coordinate systems.When a geophysicists discusses UT1 and polar motion, he usually is thinking of the angular motion of the main part of the mantle with respect to an inertial frame and to the direction of the spin axis. Since the velocities of relative motion in most of the mantle are expectd to be extremely small, even if “substantial” deep convection is occurring, the conceptual “quasi-Earth-fixed” reference frame seems well defined. Methods for realizing a close approximation to this frame fortunately exist. Hopefully, this colloquium will recommend procedures for establishing and maintaining such a system for use in geodynamics. Motion of points on the Earth’s surface and of the geocenter can be measured against such a system with the full accuracy of the new techniques.The situation with respect to celestial reference frames is different. The various measurement techniques give changes in the orientation of the Earth, relative to different systems, so that we would like to know the relative motions of the systems in order to compare the results. However, there does not appear to be a need for defining any new system. Subjective figures of merit for the various system dependon both the accuracy with which measurements can be made against them and the degree to which they can be related to inertial systems.The main coordinate system requirement related to the 5 geodynamic quantities discussed in this talk is thus for the establishment and maintenance of a “quasi-Earth-fixed” coordinate system which closely approximates the motion of the main part of the mantle. Changes in the orientation of this system with respect to the various celestial systems can be determined by both the new and the conventional techniques, provided that some knowledge of changes in the local vertical is available. Changes in the axis of rotation and in the geocenter with respect to this system also can be obtained, as well as measurements of nutation.

The spindle stage: A powerful optical tool

1988 ◽  
Vol 46 ◽  
pp. 52-53
Author(s):  
Mickey E. Gunter ◽  
F. Donald Bloss
Keyword(s):  
Significant Error ◽  
Optical Data ◽  
Refractive Indices ◽  
Axis Of Rotation ◽  
Polarizing Microscope ◽  
Microscope Stage

A single, reasonably homogeneous, nonopaque 30-to-300 μm crystal, mounted on a spindle stage and studied by immersion methods under a polarizing microscope, yields optical data frequently sufficient to identify and characterize a substance unequivocally. The data obtainable include (1) the orientation of the crystal's principal vibration axes and (2) its principal refractive indices, to within 0.0002 if desired, for light vibrating along these principal vibration axes. Spindle stages tend to be simple and relatively inexpensive, some costing less than $50. They permit rotation of the crystal about a single axis which is parallel to the microscope stage. This spindle or S-axis is thus perpendicular to the M-axis, namely the microscope stage's axis of rotation.A spindle stage excels when studying anisotropic crystals. It orients uniaxial crystals within minutes and biaxial crystals almost as quickly so that their principal refractive indices - ɛ and ω (uniaxial); α, β and γ (biaxial) - can be determined without significant error from crystal misorientation.

Multiple-fracturing and viewing of the same frozen sample at different depths using a low temperature FESEM

1996 ◽  
Vol 54 ◽  
pp. 820-821
Author(s):  
M.V. Parthasarathy ◽  
C. Daugherty
Keyword(s):  
Temperature Field ◽  
Low Temperature ◽  
Field Emission ◽  
Multiple Fracture ◽  
Precise Control ◽  
Cold Stage ◽  
Different Depths ◽  
Transfer Device

The versatility of Low Temperature Field Emission SEM (LTFESEM) for viewing frozen-hydrated biological specimens, and the high resolutions that can be obtained with such instruments have been well documented. Studies done with LTFESEM have been usually limited to the viewing of small organisms, organs, cells, and organelles, or viewing such specimens after fracturing them.We use a Hitachi 4500 FESEM equipped with a recently developed BAL-TEC SCE 020 cryopreparation/transfer device for our LTFESEM studies. The SCE 020 is similar in design to the older SCU 020 except that instead of having a dedicated stage, the SCE 020 has a detachable cold stage that mounts on to the FESEM stage when needed. Since the SCE 020 has a precisely controlled lock manipulator for transferring the specimen table from the cryopreparation chamber to the cold stage in the FESEM, and also has a motor driven microtome for precise control of specimen fracture, we have explored the feasibility of using the LTFESEM for multiple-fracture studies of the same sample.

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