This paper reviews some of the most recent advances in the application of the Hanle effect to solar physics, and how these developments are allowing us to explore the magnetism of the photospheric regions that look ``empty'' in solar magnetograms--that is, the Sun's ``hidden'' magnetism. In particular, we show how a joint analysis of the Hanle

We present a theoretical investigation on the influence of the magnetic field on the linear and circular polarization of the Ba II D2 line at 4554 Å, through the Hanle and Zeeman effects. We show in particular the existence of a differential magnetic sensitivity of the three-peak structure of the Q/I profile observed for this line, which is of

A large set of high precision full-Stokes spectro-polarimetric observations of the He I D3 line in spicules has been recorded with the ZIMPOL polarimeter at the Gregory-Coudé Telescope in Locarno. The observational technique allows us to obtain measurements free from seeing-induced spurious effects. The instrumental polarization is well under

It has recently been shown that the correct halo mass function high-mass behavior may be obtained by an appropriate treatment of the all-mass-at-center problem. Here we show that the treatment of this problem leads to an accumulated mass fraction, F, that is not a universal function of the linear variance of the density contrast but depends on the

We present a preliminary analysis of penumbral spectra observed with unprecedented angular resolution (0.2 arcsec) using the new Swedish 1-m Solar Telescope. The use of a non-magnetic line allows us to measure Doppler shifts without magnetic contamination. The observed Doppler shifts depend on the part of the line used for measuring, indicating

We reviewed the polarization properties of hydrogen lines in the presence of electric and magnetic fields. We first considered the case of completely depolarized hydrogen atoms. Under this assumption, the hydrogen lines manifest complex polarization signatures due to the combined Stark and Zeeman effect tep{c0 CL93}. One can derive convenient