Transversal segments in Hα solar filament channels

Some filament channels are inhabited not by solid filament bodies but filaments with gaps and isolated segments. Axes of some segments are directed at different angles to filament long axes deviating to the other side of them than thin threads of the fine filament structure. Obviously, the structure of a filament should be related to the distribution of photospheric magnetic fields in the filament channel. We analyse the distribution of dips in magnetic field lines of a flux rope in the framework of a simple flux-rope model under the influence of two small magnetic sources of opposite polarities. We found that isolated segments appear above the bipole when the direction of its horizontal field is antiparallel to the direction of the flux-rope axial field. This magnetic configuration becomes apparent in the shape of a polarity inversion line (PIL). Observations confirm the relationship between the shape of the photospheric PILs and filament structures.