In ideal magnetohydrodynamics, if a cylindrical flux tube of length L 0 is compressed while the length of tube stays the same, the magnetic field and the density of the tube increase with the same proportionality. If a flux tube with a configuration of a magnetic field of B 0 and a plasma density of ρ ρ 0 confined to the tube is compressed by a scalar value defined as λ λ , the new magnetic field and density are given by: B = B 0 λ λ 2 ρ ρ = ρ ρ 0 λ λ 2 If λ λ < 1 , known as transverse compression, B and ρ ρ increase and are scaled the same while transverse expansion decreases B and ρ ρ by the same value and proportion where B / ρ ρ is constant.