Horizontal convective velocity field obtained from the observations of the solar limb

Abstract

Structure of horizontal convective currents in the solar atmosphere has been investigated using profiles of the λ ≈ 532.42 nm neutral iron line which were observed at the solar limb with high spatial resolution. The asymmetry of the observed line was shown to arise when approaching the solar limb. The spatial and time velocity variations were simulated using the λ-meter technique. Acoustic waves were removed using the k-ω filters. The convection currents on various spatial scales were distinguished, namely, those connected with granulation, mesogranulation, and supergranulation. The spatial and time distribution of the convection velocities in the photosphere and in the low chromosphere has been analyzed. The horizontal currents were shown to exist on granulation, mesogranulation, and supergranulation scales as low as h ≈ 250 km, and the granulation and mesogranulation horizontal velocities increase with height. In the photospheric layers, the supergranulation vertical-velocity field appears almost invariable, while the supergranulation horizontal-velocity field can vary with height. The horizontal velocity distribution within large convection currents is found to be asymmetric on granulation, mesogranulation, and supergranulation scales.