Narrowband spectral intensity of the Lost City at 50 km altitude; comparison of the standard and modified boundary conditions. Panel a: spectral intensity with standard boundary condition; panel b: modified boundary condition: total (- - -), blue (), visible (), and red () passbands; panel c: spectral intensity of the atomic lines concerning the most abundant evaporation products computed from the standard boundary condition and; panel d: spectral intensity of the atomic lines concerning the most abundant evaporation products computed from the modified boundary condition: Si, Mg, Mg⁺, K, Fe, Fe⁺, Na, Na⁺, Ca, Ca⁺, - - - total.