P. Odert

THE EVOLUTION OF STELLAR ROTATION AND THE HYDROGEN ATMOSPHERES OF HABITABLE-ZONE TERRESTRIAL PLANETS

Terrestrial planets formed within gaseous protoplanetary disks can accumulate significant hydrogen envelopes. The evolution of such an atmosphere due to XUV driven evaporation depends on the activity evolution of the host star, which itself depends sensitively on its rotational evolution, and therefore on its initial rotation rate. In this letter, we derive an easily applicable method for calculating planetary atmosphere evaporation that combines models for a hydrostatic lower atmosphere and a hydrodynamic upper atmosphere. We show that the initial rotation rate of the central star is of critical importance for the evolution of planetary atmospheres and can determine if a planet keeps or loses its primordial hydrogen envelope. Our results highlight the need for a detailed treatment of stellar activity evolution when studying the evolution of planetary atmospheres.

EUV-driven mass-loss of protoplanetary cores with hydrogen-dominated atmospheres: the influences of ionization and orbital distance

We investigate the loss rates of the hydrogen atmospheres of terrestrial planets with a range of masses and orbital distances by assuming a stellar extreme ultraviolet (EUV) luminosity that is 100 times stronger than that of the current Sun. We apply a 1D upper atmosphere radiation absorption and hydrodynamic escape model that takes into account ionization, dissociation and recombination to calculate hydrogen mass loss rates. We study the effects of the ionization, dissociation and recombination on the thermal mass loss rates of hydrogen-dominated super-Earths and compare the results to those obtained by the energy-limited escape formula which is widely used for mass loss evolution studies. Our results indicate that the energy-limited formula can to a great extent over- or underestimate the hydrogen mass loss rates by amounts that depend on the stellar EUV flux and planetary parameters such as mass, size, effective temperature, and EUV absorption radius.

Identifying the “true” radius of the hot sub-Neptune CoRoT-24b by mass loss modelling

For the hot exoplanets CoRoT-24b and CoRoT-24c, observations have provided transit radii R-T of 3.7 +/- 0.4R(circle plus) and 4.9 +/- 0.5R(circle plus), and masses of = 5.7M(circle plus) and 28 +/- 11M(circle plus), respectively. We study their upper atmosphere structure and escape applying an hydrodynamic model. Assuming R-T +/- R-PL, where R-PL is the planetary radius at the pressure of 100 mbar, we obtained for CoRoT-24b unrealistically high thermally driven hydrodynamic escape rates. This is due to the planets high temperature and low gravity, independent of the stellar EUV flux. Such high escape rates could last only for< 100 Myr, while R-PL shrinks till the escape rate becomes less than or equal to the maximum possible EUV-driven escape rate. For CoRoT-24b, R-PL must be therefore located at approximate to 1.9-2.2R(circle plus) and high altitude hazes/clouds possibly extinct the light at R-T. Our analysis constraints also the planets mass to be 5-5.7M(circle plus). For CoRoT-24c, R-PL and R-T lie too close together to be distinguished in the same way. Similar differences between R-PL and R-T may be present also for other hot, low-density sub-Neptunes.

Aeronomical constraints to the minimum mass and maximum radius of hot low-mass planets

Stimulated by the discovery of a number of close-in low-density planets, we generalise the Jeans escape parameter taking hydrodynamic and Roche lobe effects into account. We furthermore define

How expanded ionospheres of Hot Jupiters can prevent escape of radio emission generated by the cyclotron maser instability

Lambda

Solar XUV and ENA-driven water loss from early Venus' steam atmosphere

as the value of the Jeans escape parameter calculated at the observed planetary radius and mass for the planets equilibrium temperature and considering atomic hydrogen, independently of the atmospheric temperature profile. We consider 5 and 10

Escape and fractionation of volatiles and noble gases from Mars-sized planetary embryos and growing protoplanets

M_{oplus}

Effect of stellar wind induced magnetic fields on planetary obstacles of non-magnetized hot Jupiters

planets with an equilibrium temperature of 500 and 1000 K, orbiting early G-, K-, and M-type stars. Assuming a clear atmosphere and by comparing escape rates obtained from the energy-limited formula, which only accounts for the heating induced by the absorption of the high-energy stellar radiation, and from a hydrodynamic atmosphere code, which also accounts for the bolometric heating, we find that planets whose

Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating

Lambda

Indications of stellar prominence oscillations on fast rotating stars: the cases of HK Aqr and PZ Tel

is smaller than 15-35 lie in the boil-off regime, where the escape is driven by the atmospheric thermal energy and low planetary gravity. We find that the atmosphere of hot (i.e.