top panel: deposition rates due to the absorption of the stellar soft X-rays (λ ~ 1–10 nm, dashed curve) and the extreme ultraviolet radiation (EUV, λ ~ 10–100 nm, dotted line) as well as the total XUV radiation (solid line). Bottom panel: total deposition rate W_hν (solid curve) of the stellar XUV radiation, the rate W_pe (dashed curve) of energy accumulation by the fresh photoelectrons due to the photolytic processes (1)and (2), and the heating rate W_T (dotted curve) by photoelectrons due to the electron impact processes (5) in the H₂ → H transition region in the upper atmosphere of HD 209458b.