Sunspots display a nearly horizontal outflow of material in their penumbrae called the Evershed flow (EF), whose physical driving mechanisms are still not fully understood. One way to address this problem is to consider a reversed EF, i.e. a flow going from the outer penumbra to the inner penumbra in the photospheric layers, opposite to the typical direction of the EF.
Such an anomalous EF was observed with the spectropolarimeter on board the Japanese Hinode spacecraft. In this work we study this penumbral inflow (to our knowledge the first observation of an inverse EF in the photosphere) and compare its properties with the well-known normal Evershed outflow.
For this, we determine the 3-D structure of the magnetic field vector, the velocity field, temperature, etc. of this special sunspot and invert the data using the SPINOR code in its 2D coupled mode. The resulting height-dependent maps of the relevant physical parameters in the sunspot show astonishing similarities between the normal and the anomalous EF, but also reveal distinct differences, for example in the radial temperature distribution.