Global 3D hydrodynamic modelling of absorption in Ly α and He 10830 A lines at transits of GJ3470b

Warm Neptune GJ3470b has been recently observed in 2³S-2³P transition of metastable helium, yielding absorption of about 1 per cent in Doppler velocity range of [-40; 10] km s^-1. Along with previous detection of absorption in Ly α with depth of 20-40 per cent in the blue and red wings of the line, it offers a complex target for simulation and testing of the current models. Obtained results suggest that absorption in both these lines comes from interaction of expanding upper planetary atmosphere with stellar plasma wind, allowing to constrain the stellar plasma parameters and the helium abundance in planet atmosphere.