Research
Jupiter's atmospheric circulation
The cloud layer of Jupiter is divided into dark and bright bands that are shaped by strong east-west winds. Such winds in planetary atmospheres are thought to be tied with a meridional circulation. The Juno mission collected measurements of Jupiter's atmosphere at various wavelengths, which penetrate the cloud cover. We show, using the Juno data, that Jupiter possesses 8 circulation cells in each hemisphere encompassing the east-west winds, gaining energy from atmospheric waves, and extending at least to a depth of hundreds of kilometers. Different than Earth, which has only 1 analogous cell in each hemisphere, known as a Ferrel cell, Jupiter can contain more cells due to its larger size and faster spin. The presented results shed light on the unseen flow structure beneath Jupiter's clouds. [Read more]
Simulationg gas giants atmospheres
Jupiter's atmosphere consists of a number of dynamical regimes: the equatorial superrotation and its adjacent retrograde jets, the midlatitude, eddy-driven, alternating jet streams, and the associated meridional cells and the turbulent polar region. While intensive research has been conducted in the past decades on each of these regimes, they all remain only partially understood and somewhat mysteries. Different models give a variety of possible explanations for each of these regions, and only a handful of models can even capture two areas at once. To our knowledge, no model claimed to capture all three regions simultaneously yet. We perform numerical simulations using the Rayleigh convection model that can reproduce the midlatitudinal pattern of the mostly barotropic, alternating eddy-driven jets and the meridional circulation cells accompanying them. As expected for a gas giant, we find that the vertical eddy momentum fluxes are just as important as the meridional eddy momentum fluxes, which drive the midlatitudinal circulation on Earth.
Studies have shown that the rotation rate, the forcing scheme, and the Rayleigh number are also responsible for the emergence of jets in simulations of gas giants, but we keep these constant in our simulations. Our simulations also capture the tilted convection columns in the tangent cylinder region, leading to the superrotation at the equator and the adjacent, subrotating jets. Our analysis provides another step towards understanding the deep atmospheres of gas giants. [Read more]
The deep flow structures of Jupiter
Jupiter's north-south asymmetric gravity field, as measured by the Juno spacecraft, currently orbiting Jupiter, has been used to set the depth of its jet streams (associated with the famous visible cloud bands) at approximately ∼3,000 km. This estimate was based on all the gravity field measurements combined. However, there is also information about the structure of the flow hidden in each individual measurement. We analyze these measurements and show how each of them constrains the flow at a different depth. We also systematically investigate the statistical likelihood of wind profiles that differ from the profile observed at the cloud level with various structures at depth. We find that Jupiter's measured cloud-level jet streams fit with its gravity data only for a relatively narrow envelope of vertical structures. Although other jet profiles that are different from the one observed at the cloud level are feasible (still consistent with the gravity data), they are statistically unlikely. Finally, we explore a depth-dependent wind structure inspired by the Juno microwave radiometer instrument, which indicates that ammonia abundance varies with depth and might be correlated with the jet streams. We find that such a profile can still match the gravity data as long as the variation from the cloud-level wind is not substantial. [Read more]
Magnetic field constraints on Jupiter's zonal jets
Jupiter's internal flow structure is still not fully known, but can be now better constrained due to Juno's high-precision measurements. The recently published gravity and magnetic field measurements have led to new information regarding the planet and its internal flows, and future magnetic measurements will help to solve this puzzle. We propose a new method to better constrain Jupiter's internal flow field using the Juno gravity measurements combined with the expected measurements of magnetic secular variation. Based on a combination of hydrodynamical and magnetic field considerations we show that an optimized vertical profile of the zonal flows that fits both measurements can be obtained. Incorporating the magnetic field effects on the flow better constrains the flow decay profile. This will get us closer to answering the persistent question regarding the depth and nature of the flows on Jupiter. [Read more]
