  Warm Neptune GJ3470b has been recently observed in 23S-23P transition of
metastable helium, yielding absorption of about 1% in Doppler velocity range of
[-40; 10] km/s. Along with previous detection of absorption in Ly{\alpha} with
depth of 20-40% 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.
