Illustration of modeled 3D atomic hydrogen coronae for 3 XUV (current flux in the habitable zone of GJ 436). Presented is a slice of modeled 3D domain for − 10⁶ < z < 10⁶ m. Left panel: nitrogen-dominated atmosphere. Middle panel: nitrogen-dominated atmosphere with Earth-like hydrogen content. Right panel: hydrogen-dominated atmosphere. All dots show simulated metaparticles of the exosphere of a planet, and stellar wind. The red dots symbolize stellar wind protons, the blue dots are the neutral atmospherichydrogen particles, the light blue dots are neutral nitrogen atoms and, finally, the yellow dots are ionized planetary N+. The green dots are ionized planetary hydrogen atoms (H+ of planetary origin). The black dot in the center of each plot symbolizes the planet, the white area around it is the lower atmosphere which is not included in the DSMC simulation. For nitrogen-dominated atmospheres, the lower atmosphere is very close to the planetary surface, so that the white area is not visible on the plots due to scaling. The star is on the right, and the stellar wind is coming from the right side.