Calendar

Very Hot Super-Earths with an Atmosphere: A Model Explaining Their Paradoxical Existence

The aim of this research is to constrain the interior structures and evolutions of hot super-Earths, particularly that of 55 Cancri e. Herewith, we propose an alternative model for the paradoxical nature of small, hot super-Earths with atmospheres. Our model does not require these bodies to contain large quantities of ices in order to account for their low densities, which has been a subject of dispute considering their high surface temperatures and the potentially strong internal heat processes such as tidal flexing or radiogenic heating. The first aspect of our research involved calculating the total H₂ reservoir in 55 Cancri e which is ~ 2×10²³ kg (0.04 M_⨁). We then encountered a theoretical enigma since the UV and X-Ray induced mass loss should have been strong enough to evaporate the atmosphere billions of years ago, which is inconsistent with astronomical data showing a currently plentiful atmosphere. This issue can be completely avoided by showing that for a tidally locked setup, the mass loss rates on the night-side are negligible thus allowing the planet to maintain a H₂-rich atmosphere above half its surface. In the case of 55 Cancri e, it became tidally locked approximately 50 ± 250 Myrs after it formed implying that from that moment onwards the radius and mass of the body changed negligibly. Prior to this time mass loss rates were very strong and approximately homogeneous which when modelled, showed that 55 Cancri e was born as a Neptunian-or-Jovian-type exoplanet. Finally, we propose that the bimodal distribution in exoplanet radii may be the result of two different evolutionary paths; one where a super-Earth loses all of its atmosphere before it becomes tidally locked (resulting in the peak at ~ 1.3 R_⨁), and the other when super-Earths become tidally locked before losing their atmosphere allowing them to maintain it (resulting in the other peak at ~ 2.4 R_⨁).

The cosmic ray (CR) spectrum detected at Earth is a non-trivial combination of the spectrum released by the sources and of the CR propagation and interaction with the interstellar medium (ISM). CRs in the ISM are scattered by the turbulent magnetic field, and, depending on their energy and species, they can incur in severe energy losses. In addition, CRs  can  themselves  excite  magnetic  turbulence  in  the background plasma and generate large scale flows like galactic winds, thus affecting  their own  transport.
In this talk I will discuss some  implications of the CR-ISM interaction, in particular  the formation of galactic winds,  the CR escape and propagation in the source proximity, the identification of the sources of TeV CR electrons and  the ionization of molecular clouds.