Normal and counter Evershed flows in the penumbra of sunspots : HINODE observations and MHD simulations Sunspot penumbrae harbor a distinctive gas outflow in the photosphere known as the Evershed flow whose origin has been an open question since its discovery in 1909. More recently the existence of counter Evershed flows (inflows) in well developed penumbrae was detected. Little is known about their nature characteristics and their relation with the filamentary structure of penumbrae due to their rare occurrence. This thesis reports a detailed study of the most prominent counter Evershed flow (CEF) so far recorded. Similarities and differences in the flow characteristics and the fine stru...