Nonthermal Atmospheric Losses for the Exoplanet GJ 3470b

• Published in: Astronomy reports Vol. 66; no. 12; pp. 1254 - 1261
• Main Authors: Avtaeva, A. A., Shematovich, V. I.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.12.2022; Springer Nature B.V
• Subjects: Astronomy; Atmosphere; Atmospheric models; Dissociation; Energy spectra; Extrasolar planets; Fluctuations; Gas giant planets; Hydrogen; Hydrogen atoms; Mathematical models; Observations and Techniques; Photochemicals; Physics; Physics and Astronomy; Planetary atmospheres; Stellar activity; Stellar planets; Upper atmosphere; atmospheric photochemistry; exoplanet; atmospheric nonthermal losses; suprathermal atoms
• ISSN: 1063-7729; 1562-6881
• DOI: 10.1134/S1063772922110051

In this work, numerical estimates of the rate of nonthermal loss of the atmosphere of a hot exoplanet due to exothermic photochemical processes are obtained. As an example, calculations were made for the Н 2 → Н transition region of the upper atmosphere of the hot Neptune GJ 3470b in the altitude range 1.6‒2.05 R p . From the obtained energy spectrum of the flux of suprathermal hydrogen atoms formed due to the processes of dissociation of Н 2 molecules and escaping from the atmosphere through the upper boundary of the transition region, an estimate equal to 3.4 × 10 13 cm –2 s –1 was derived for the numerical escape flux in the planet-star direction under conditions of a moderate level of stellar activity. This calculated value of the numerical escape flux of suprathermal hydrogen atoms is close to the value of the numerical flux of thermal hydrogen atoms calculated by the Jeans formula for the data of the aeronomic model and equal to 3.3 × 10 13 cm –2 s –1 . The calculated atmospheric mass loss flux averaged over the illuminated hemisphere of the upper atmosphere is 9.5 × 10 9 g/s at the upper boundary of the transition region. It can be concluded that nonthermal processes in the modeling of exoplanet atmospheres should be considered as one of the important factors determining the atmospheric mass loss, especially for hot exoplanets from the families of sub-Neptunes and super-Earths.