Crossing Filaments
  Solar filaments show the position of large scale polarity inversion lines and are used for the reconstruction of large-scale solar magnetic field structure on the basis of H{\alpha} synoptic charts for the periods when magnetographic measurements were not available. Sometimes crossing filaments are seen in H{\alpha} filtergrams. We analyze daily H{\alpha} filtergrams from the archive of Big Bear Solar Observatory for the period of 1999-2003 to find crossing and interacting filaments. A number of examples are presented and filament patterns are compared with photospheric magnetic field distributions. We have found that all crossing filaments reveal quadrupolar magnetic configurations of the photospheric field and presume the presence of null points in the corona. 
Boris Filippov and A.K. Srivastava
astro-ph.SR