2-D multiline spectroscopy of the solar photosphere ^*

¹ Dipartimento di Fisica, Università di Roma Tor Vergata, V.le Ricerca Scientifica 1, 00133 Roma, Italy
² Istituto di Fisica dello Spazio Interplanetario-CNR, Area di Ricerca Tor Vergata, 00133 Roma, Italy
³ Dipartimento di Fisica, Università di L'Aquila, Località Coppito, 67010 L'Aquila, Italy
⁴ Dipartimento di Fisica, Università della Calabria, 87036 Rende (CS), Italy

Corresponding author: F. Berrilli, berrilli@roma2.infn.it

Received: 11 May 2001
Accepted: 4 September 2001

Abstract

The structure and dynamics of the photosphere are investigated, with time series of broadband and monochromatic images of quiet granulation, at the solar disk center. Images were acquired with the IPM observing mode at the THEMIS telescope. Velocity and line center intensity fields, derived from the observation of three different photospheric lines, are used to study velocity and intensity patterns at different heights in the photosphere. Automatic segmentation procedures are applied to velocity and intensity frames to extract solar features, and to investigate the dependence of their properties at different scales and heights. We find a dependence of the statistical properties of upflow and downflow regions on the atmospheric height. Larger granules, passing through a great part of the photosphere, are used to investigate the damping of convective motions in stably stratified layers. The results suggest the occurrence of an intense braking in the deep photosphere (first ~120 km). Furthermore, we investigate the temporal and spatial evolution of velocity fields, deriving typical time scales of dynamical processes relative to different solar features. In particular, for two selected isolated exploders, we reveal a velocity deceleration in the central region since the early phase of their fragmentation.