3D photospheric velocity field of a supergranular cell

Dipartimento di Fisica, Università di Roma “Tor Vergata”, 00133 Roma, Italy e-mail: delmoro@roma2.infn.it

Received: 3 April 2007
Accepted: 25 May 2007

Abstract

Aims.We investigate the plasma flow properties inside a supergranular (SG) cell, in particular its interaction with small-scale magnetic field structures.

Methods.The SG cell has been identified using the magnetic network (CaII wing brightness) as a proxy, applying Two-Level Structure Tracking (TST) to high spatial, spectral and temporal resolution observations obtained by IBIS. The full 3D velocity vector field for the SG has been reconstructed at two different photospheric heights. We also computed the mean radial flow of the SG by cork tracing and studied the behaviour of the horizontal and Line of Sight plasma flow cospatial with the cluster of bright CaII structures of magnetic origin to better understand the interaction between photospheric convection and small-scale magnetic features.

Results.The SG cell we investigated seems to be organized with an almost radial flow from its centre to the border. The large-scale divergence structure is probably created by a compact region of constant up-flow close to the cell centre. On the edge of the SG, isolated regions of strong convergent flow are nearby or cospatial with extended clusters of bright CaII wing features forming the knots of the magnetic network.