A broad pattern of FIBRILS in the CHROMOSPHERE, marking where a FILAMENT may soon form or where a filament recently disappeared.
ON-LINE GLOSSARY OF SOLAR-TERRESTRIAL TERMS of National Geophysics Data Center

A broad pattern of FIBRILS in the CHROMOSPHERE, marking a portion of a magnetic polarity inversion line where a filament may soon form or where a filament recently disappeared. Filament channels interconnect separate filaments and active regions on a common inversion line.