Schematic diagram of the magnetic field and plasma configuration. The blue smaller cylinder represents the flowing thread inside the magnetic tube which is represented by the larger white cylinder. The length of the magnetic tube is 2L and the length of the filament thread is 2W. The density of the thread is ρ_p, the density of the magnetic tube is ρ_e, and the density of the outer corona is ρ_c. The thread is moving along the axis of the tube with velocity v₀.