Structure of convective flows on supergranular scales in the solar photosphere

Abstract

The exploration of the velocity field of the real solar convection was performed using neutral iron line λ ≈ 639.3 nm profile from the observations with high spatial resolution. The inverse procedure was applied for each profile to reproduce the velocity field in the solar photosphere. Acoustic waves were removed by k − ω filtration. To study supergranulation in the solar photosphere we selected motions with horizontal velocities less than 0.5 km/s. As the lifetime of the supergranule is larger than the observation time, we have averaged images of the vertical velocity in time. Supergranulation becomes more apparent on the distribution of the vertical velocity (the range of ∆V variations on the supergranular scales is constrained by ∼ 0.04 km/s). The velocity field within such cells has been studied and compared with the distributions of the vertical velocity on smaller scales. The upward supergranular flows expand with height and intensify (as distinct from decreasing of the velocity variations on the smaller scales), and the distribution of the line of sight velocity inside supergranular flows becomes more asymmetric in the higher layers of the photosphere. The downward supergranular flows are more compact and have a complicated structure too.