Luca Belluzzi; Istituto Ricerche Solari Locarno (IRSOL), Switzerland \\ Javier Trujillo Bueno; Instituto de Astrofísica de Canarias (IAC), Spain

The scattering polarization signal of the Ca I line at $4227$ angstrom shows a peculiar triple-peak profile, with a sharp peak in the line core and broader peaks in the wings. This structure is due to frequency coherence in line scattering processes and cannot be modeled under the assumption of complete redistribution in frequencies (CRD). Since the Hanle effect operates in the line core region only, it has generally been thought that the amplitude of the scattering polarization wing lobes is insensitive to the presence of weak magnetic fields. However, recent theoretical investigations have shown that such wing lobes are in fact sensitive to the magnetic field through another physical mechanism, namely the magneto-optical (MO) effects that rotate the plane of linear polarization as radiation propagates through the solar atmosphere. Here, the expected signatures of such mechanism are discussed, focusing on the implications for magnetic field diagnostics in quiet or weakly magnetized regions of the solar atmosphere.

Luca Belluzzi (belluzzi@irsol.ch), IRSOL (Istituto Ricerche Solari Locarno); Javier Trujillo Bueno (jtb@iac.es), IAC (Instituto de Astrofísica de Canarias)

The scattering polarization signal of the Ca I line at 4227 angstrom shows a peculiar triple-peak profile, with a sharp peak in the line core and broader peaks in the wings. This structure is due to frequency coherence in line scattering processes and cannot be modeled under the assumption of CRD. Since the Hanle effect operates in the line core region only, it has generally been thought that the amplitude of the scattering polarization wing lobes is insensitive to the presence of weak magnetic fields. However, recent theoretical investigations have shown that such wing lobes are in fact sensitive to the magnetic field through another physical mechanism, namely the magneto-optical effects that rotate the plane of linear polarization as radiation propagates through the solar atmosphere. Here, the expected signatures of such mechanism are discussed, focusing on the implications for magnetic field diagnostics in quiet or weakly magnetized regions.