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SUMMARY:Photoevaporation from Exoplanet Atmospheres: Understanding the Rol
 e of Stellar Winds and Considering Water-rich Atmospheres - Laura Harbach 
 (Imperial)
DTSTART:20240206T130000Z
DTEND:20240206T140000Z
UID:TALK210823@talks.cam.ac.uk
CONTACT:Dr Emily Sandford
DESCRIPTION:The atmospheres of close-in exoplanets are extremely vulnerabl
 e to the effects of stellar UV to X-ray radiation. Photoevaporation can si
 gnificantly alter planetary atmospheres or even strip them entirely\, pote
 ntially rendering a planet uninhabitable. Understanding how these atmosphe
 res evolve\, persist\, or fade away remains a fundamental challenge. In th
 is talk\, I will discuss two distinct but interconnected areas of photoeva
 porative research. \n\n \n\nFirstly\, I will discuss the interaction betwe
 en the stellar wind and photoevaporating atmospheres. I will present 3D ma
 gnetohydrodynamic simulations of the interaction between the stellar wind 
 and the photoevaporating outflow of a planet orbiting an M dwarf. This ana
 lysis reveals a diverse range of magnetosphere morphologies and plasma dis
 tributions due to the wind-outflow interaction. I consider how these chang
 ing morphologies might impact observable hydrogen Lyman-alpha signatures d
 uring planetary transits. \n\n \n\nIn the second part\, I will delve into 
 our current understanding of photoevaporation from water-rich atmospheres.
  Conventional analytic approaches often oversimplify the process\, assumin
 g two scenarios: the escape of only lighter hydrogen\, or the dragging of 
 oxygen along with escaping hydrogen. These two scenarios lead to two end c
 ases: a planet that has retained its water-rich atmosphere or a planet whi
 ch has lost its atmosphere\, becoming dry and desiccated. I will challenge
  these oversimplifications by presenting results from a novel 1D multiflui
 d hydrodynamic model of photoevaporation from a water-rich atmosphere\, wh
 ich shows oxygen escape should no longer be described by a simple on/off s
 witch but instead requires careful modelling.
LOCATION:Hoyle Committee Room + ONLINE - Details to be sent by email
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