The shapes of weak fraunhofer lines, including their asymmetry, are explained by the influence of acoustic waves and granular motions. The following pattern of granula is adopted: the ascending (granular) and descending (intergranular) velocities V1 and V2 as well as the relevant temperatures T1 and T2 are maximum (minimum) at the center of granula (intergranula) and decrease (increase) sinusoidally outwards. There is also tangential outflow of the matter from the center of granula with the velocity V3 = const. and temperature T3 equal to the temperature of the photospheric model T0. The areas occupied by ascending, descending, and tangential motions are S1, S2, S3 respectively.

The inhomogeneities caused by granulation are perturbed by the acoustic waves with the velocity amplitude V0 = 0.4 km/s and with the period T = 300 sec. The formula for the absorption line coefficient was derived, and the center-to-limb profiles of 11 weak fraunhofer lines were calculated. The comparison of calculated and observed line profiles have resulted in determining “best fit” values of V1, V2, V3, S1, S2, S3 and ΔT = T1 - T2. Tangential motions occupy the larger part of the solar surfaces S3 = 0.7, V3 ≈ 2.7 km/s, V ≈ 1.0 km/s, ΔT ranges between 270° - 400°.