Michael Roman's research while affiliated with University of Leicester and other places

Publications (11)

Article
Full-text available
Ultrahot Jupiters represent an exciting avenue for testing extreme physics and observing atmospheric circulation regimes not found in our solar system. Their high temperatures result in thermally ionized particles embedded in atmospheric winds interacting with the planet’s interior magnetic field by generating current and experiencing bulk Lorentz...
Article
The advent of high-resolution spectroscopy ( R ≳ 25,000) as a method for characterization of exoplanet atmospheres has expanded our capability to study nontransiting planets, vastly increasing the number of planets accessible for observation. Many of the most favorable targets for atmospheric characterization are hot Jupiters, where we expect large...
Preprint
Full-text available
The advent of high-resolution spectroscopy as a method for exoplanet atmospheric characterization has expanded our capability to study non-transiting planets, increasing the number of planets accessible for observation. Many of the most favorable targets for atmospheric characterization are hot Jupiters, where we expect large spatial variation in p...
Preprint
Full-text available
Ultra-hot Jupiters represent an exciting avenue for testing extreme physics and observing atmospheric circulation regimes not found in our solar system. Their high temperatures result in thermally ionized particles embedded in atmospheric winds interacting with the planet's interior magnetic field by generating current and experiencing bulk Lorentz...
Article
Observations of scattered light and thermal emission from hot Jupiter exoplanets have suggested the presence of inhomogeneous aerosols in their atmospheres. 3D general circulation models (GCMs) that attempt to model the effects of aerosols have been developed to understand the physical processes that underlie their dynamical structures. In this wor...
Preprint
Using a general circulation model (GCM), we investigate trends in simulated hot Jupiter atmospheres for a range of irradiation temperatures (1,500 - 4,000 K), surface gravities (10 and 40 m s-2), and cloud conditions. Our models include simplified temperature-dependent clouds with radiative feedback and show how different cloud compositions, vertic...
Preprint
Observations of scattered light and thermal emission from hot Jupiter exoplanets have suggested the presence of inhomogeneous aerosols in their atmospheres. 3D general circulation models (GCMs) that attempt to model the effects of aerosols have been developed to understand the physical processes that underlie their dynamical structures. In this wor...
Article
Using a general circulation model with newly implemented cloud modeling, we investigate how radiative feedback can self-consistently shape condensate cloud distributions, temperatures, and fluxes in a hot Jupiter atmosphere. We apply a physically motivated but simple parameterization of condensate clouds in which the temperature determines the clou...
Preprint
Using a general circulation model with newly implemented cloud modeling, we investigate how radiative feedback can self-consistently shape condensate cloud distributions, temperatures, and fluxes in a hot Jupiter atmosphere. We apply a physically motivated but simple parameterization of condensate clouds in which the temperature determines the clou...
Article
Motivated by the observational evidence of inhomogeneous clouds in exoplanetary atmospheres, we investigate how proposed simple cloud distributions can affect atmospheric circulations and infrared emission. We simulated temperatures and winds for the hot Jupiter Kepler-7b using a three-dimensional atmospheric circulation model that included a simpl...

Citations

... Recent high spectral resolution observations of ultra-hot Jupiters have found a wealth of metallic species along with evidence for thermal inversions (Nugroho et al. 2017, Hoeijmakers et al. 2018, Jensen et al. 2018, Seidel et al. 2019, Cabot et al. 2020, Hoeijmakers et al. 2020, Nugroho et al. 2020, Yan et al. 2020, Kasper et al. 2021, Kesseli & Snellen 2021, Tabernero et al. 2021, Yan et al. 2022. The hot daysides of ultra-hot Jupiters should be sufficiently ionized that magnetohydrodynamic mechanisms can affect their atmospheric circulation (Perna et al. 2010, Menou 2012, Batygin et al. 2013, Rauscher & Menou 2013, Rogers & Showman 2014, Rogers & Komacek 2014, Hindle et al. 2019, Beltz et al. 2022, potentially causing large-amplitude time-variability due to induced atmospheric magnetic fields (Rogers 2017, Rogers & Mcelwaine 2017, Hindle et al. 2021a. Additionally, many ultra-hot Jupiters are highly inflated, implying a significant internal heat flux (Thorngren & Fortney 2018, Thorngren et al. 2019, Sarkis et al. 2021) that can affect their deep atmospheric circulation and mixing (Tremblin et al. 2017, Sainsbury-Martinez et al. 2019, Carone et al. 2020, Baeyens et al. 2021. ...
... First, we regrid the GCM's 65 vertical layers in pressure to 250 layers at constant altitude, by assuming vertical hydrostatic equilibrium, consistent with the GCM. 1 This is necessary in order to calculate line-of-sight columns and to increase the spatial resolution of the radiative transfer simulations. Based on resolution tests performed by Malsky et al. (2021), this number of altitude layers should be sufficient to accurately calculate the emergent spectra. ...
... Due to its idealized nature, our model setup has a variety of limitations that must be addressed before detailed comparison with observations of ultra-hot Jupiters. Most notably, as in many recent GCM studies of exoplanet atmospheric dynamics and its impact on observations (e.g., Dietrick et al. 2020, May & Rauscher 2020, Mendonça 2020, Roman et al. 2021, Beltz et al. 2021, Harada et al. 2021, May et al. 2021, Beltz et al. 2022, our model utilizes a double-gray radiative transfer scheme. Though double-gray schemes provide a simplified yet realistic framework within a GCM to gain physical insight into the processes that regulate atmospheric dynamics and heat transport, Lee et al. (2021) recently demonstrated that GCMs with double-gray radiative transfer provide an inadequate representation of the thermal structure compared to those with band-gray or fully non-gray radiative transfer schemes. ...
... Unlike the other processes at work in ultra-hot Jupiter atmospheres, aerosols and their radiative feedback on the circulation likely has a more minor effect on the atmospheric dynamics of ultra-hot Jupiters than for hot Jupiters due to the high temperatures preventing condensation of many mineral species (for a comprehensive recent review of exoplanet aerosols, see . Given the high temperatures on the daysides of both hot and ultra-hot Jupiters and large horizontal temperature contrasts, it is expected that their aerosol coverage is non-uniform, with enhanced condensate cloud coverage on the cooler western limb and nightside and with haze distributions dependent on particle size , Kempton et al. 2017, Wakeford et al. 2017, Mendonça et al. 2018, Powell et al. 2018, 2019, Gao et al. 2020, Helling et al. 2021, Roman et al. 2021, Steinrueck et al. 2021, Robbins-Blanch et al. 2022). There is observational evidence of such non-uniform aerosol distributions from the reflected light signature in Kepler phase curves (Demory et al. 2013, Esteves et al. 2015, Hu et al. 2015, Schwartz & Cowan 2015, and both low and high resolution transmission spectra have been suggestive of non-uniform aerosol coverage that changes with local atmospheric temperature (Line & Parmentier 2016, Sing et al. 2016. ...
... The observational evidence for non-uniform aerosol distributions in hot and ultra-hot Jupiter atmospheres necessitates three-dimensional models of their coupled atmospheric circulation and aerosol distribution. A range of models have been developed that incorporate the radiative feedback of aerosols on the atmospheric circulation of hot Jupiters , Lines et al. 2018, 2019, Roman & Rauscher 2019, Roman et al. 2021, Christie et al. 2021. Models that include cloud-radiative feedback are especially critical for understanding the behavior of patchy clouds on atmospheric circulation. ...
... In addition to enabling higher resolution spectra, postprocessing can be necessary for GCM models that have simplified radiative transfer schemes (e.g. grey or semigrey) (e.g., Mendonça et al. 2018a;Roman & Rauscher 2017, 2019. Lastly, post-processing allows users to approximate the effect of clouds if they are not already included within the GCM calculation, or if the cloud calculation is simplified to allow for increased computational efficiency. ...