Upper left: the total sodium production rate calculated for Phaethon, as a function of heliocentric distance within ∼1 au of the Sun (from 45 days pre-perihelion). Upper right: the location of the sodium sublimation front as a function of the angular distance from the north pole (the colatitude) at perihelion. Middle left: the sodium abundance as a function of depth at latitude 76° S at perihelion, normalized to the initial abundance. Middle right: the pressure created by sodium volatilization as a function of depth for a few rotational phases for 76° S at perihelion. Lower left: the corresponding force caused by the sodium pressure gradient shown in the middle right figure.