20 November 2024: Matt Lodge (Bristol)

Speaker: Matt Lodge (University of Bristol)

Date: Wednesday 20 November 2024

Time: 15:00

Location: Physics 3.29

Aerosols are not Spherical Cows: The Effects of Aggregates in Exoplanet Atmospheres

To fully understand the structure and composition of exoplanet atmospheres, it is crucial to be able to correctly model the absorptive properties of aerosol particles. These ubiquitous solids (in the form of dust and haze) have been shown to have a significant impact on the energy balance on Earth, as well as almost every other major body in the solar system, and it is predicted that they play an equally critical role in the atmospheres of exoplanets. Rigorous analyses such as the discrete dipole approximation (DDA) can be used to obtain accurate absorption cross-sections, but these require significant computing time, often to the point of being impractical to use. As a result, most exoplanet models make an assumption that all particles are spherical to simplify the calculations, but in this talk I show that this assumption can significantly underestimate absorption (by factors of up to 1,000). I present a powerful new model: MANTA-Ray (Modified Absorption of Non-spherical Tiny Aggregates in the RAYleigh regime). MANTA-Ray can be used to calculate absorption cross-sections within 10-20% of the values predicted by DDA, but it is 10¹³ times faster to use. In addition, I discuss comparisons of DDA models with laboratory data, as well as the wider context of how the aggregates behave differently to spheres in terms atmospheric dynamics, and the resulting effect that this has on transmission spectra.