Aims:   Study the global properties of the magnetic flux tubes forming active regions. This provides important informations on:
   the origin of these flux tubes (formation,and transport in the convective zone)
   the "boundary conditions" for flares and coronal mass ejections.

Lòpez Fuentes, M.C., Démoulin, P., Mandrini, C.H., Pevtsov, A.A.,
                van Driel-Gesztelyi, L.,
                Magnetic Twist and Writhe of Actives Regions
         2003, A&A, 397, 305    PS gzip
van Driel-Gesztelyi L., Malherbe J.M., Démoulin P.,
                Emergence of a U-loop-sub-photospheric link  between solar active regions
         2000,  A&A, 364, 845  PS gzip
López Fuentes M., Démoulin P., Mandrini C.H.,  van Driel-Gesztelyi L.,
                The Counter-kink Rotation of a Non-Hale Active Region
         2000, ApJ, 544, 540   PS gzip
Deng Y.Y., Schmieder B., Mandrini C.H., Khan J.I., Démoulin P.,  Rudawy P.,
                The evolution from birth to decay of a  short-lived active region
         1999, A&A, 349, 927  PS gzip