Thaddeus Komacek

Abstract:

Abstract The atmospheres of hot Jupiters lie in a dynamical regime without a solar system analogue. The strongly irradiated daysides reach temperatures sufficiently hot for substantial thermal ionization of atmospheric species, resulting in flows that can interact with the planetary magnetic field. These magnetic effects can significantly impact wind speeds, atmospheric temperatures, and large-scale circulation patterns. Previous work combining 3D atmospheric models and magnetic prescriptions has shown the impact of magnetic effects on temperature and velocity profiles are dependent on local atmospheric properties as well as the set of assumptions employed by the magnetic prescription. In this work, we examine a commonly employed magnetic model—a perfectly aligned dipole—in 3D General Circulation Models (GCMs) and extend this framework to allow for tilting of the deep-seated internal magnetic dipole field relative to the axis of rotation. We find that the inclusion of a tilted dipole introduces pronounced north-south asymmetries into the temperature profile leading to latitudinally shifted hotpots and deflection of winds that would otherwise be axially symmetric. We additionally simulate JWST/NIRSpec phase curves. We find that the strength of the magnetic field has the most significant effect on the simulated phase curves, with stronger magnetic fields increasing the amplitude of the phase curve and reducing the hot spot offset. Our model can provide qualitative insight into how the magnetic dipole strength or orientation may influence the large scale atmospheric dynamics and represents one of the most sophisticated incorporations of magnetic effects in GCMs for hot Jupiter atmospheres to date.

Abstract:

ABSTRACT Photochemical haze, a common aerosol type expected to form in the atmospheres of hot-Jupiters, can become concentrated to different extents between the morning and evening limbs depending on the balance between advection, gravitational settling, and radiation pressure. We present a analytical framework incorporating the effect of gravity, planetary radius, and stellar flux, alongside the particle size of the haze on its resulting relative distribution between the two limbs. Using this framework and further comparing with 3D climate simulations, our framework provides a reasonable first-order estimate of the maximum radius of haze particles which would reach the morning limb and subsequently be trapped by the nightside gyres, resulting in a higher or comparable concentration of haze over the morning limb compared to the evening limb for a given hot-Jupiter atmosphere. We find that the framework performs best for higher-gravity planets, where the transport of haze particles is more strongly controlled by gravitational settling and therefore less sensitive to the approximations made in describing the atmospheric circulation. We further show that for low-gravity hot-Jupiters, even large haze particles can be readily transported to the morning limb before being removed by gravitational settling, whereas for high-gravity hot-Jupiters only small particles can survive transport to the morning limb. Our novel framework provides a rapid way to understand the transport of haze and plan limb asymmetry observations with James Webb Space Telescope, constraining the parameter space exploration for full-scale computationally expensive 3D simulations.

Abstract:

Recent JWST transmission and emission spectroscopic observation of hot Jupiters have demonstrated that sub-micron sized silicate mineral clouds may be common hot Jupiter atmospheres. In addition, ground-based high-resolution spectroscopic observations of both transit and eclipse have implied horizontal asymmetries that may be amplified by clouds. Silicate mineral clouds have long been predicted to form and persist on the nightside and western dayside of hot Jupiters by cloud microphysical models and 3D General Circulation Models. Given the capability of current ground-based high resolution spectrographs, complementary JWST observations, as well as recent advancements in modelling techniques, the time is right to determine the prevalence and spatial and particle size distribution of mineral clouds across the parameter regime of hot Jupiters. This effort will provide a detailed test of our present theoretical understanding of cloud nucleation, transport and growth processes, and the radiative feedback of clouds on the atmospheric circulation and climate of hot Jupiters. In this work, we present a combination of analytical and numerical models of the vertical mixing of mineral clouds in hot gas giant atmospheres. Our scaling analyses naively predict that clouds of a broad range of particle sizes (up to 10 microns) should be well-mixed throughout gas giant atmospheres to low pressures (~0.1 mbars). However, the local nature of vertical mixing in more detailed three-dimensional simulations prevents such well-mixed micron-sized mineral clouds in many cases. In addition, we hypothesise that fragmentation may play a role in setting the characteristic maximum particle size of silicate mineral clouds in hot Jupiter atmospheres, much like it impacts the build-up of silicate grains in protoplanetary disks. We predict how mixing scales with cloud particle size and composition using analytic theory and three-dimensional numerical simulations including cloud tracers. We discuss implications for ground-based high resolution characterisation of hot Jupiters, especially with time-resolved spectroscopy.