Magnetocapillary Instability of Non--Conducting Liquid Jets Revisited : Plateau versus Chandrasekhar

The magnetostatic and magnetocapillary instability problems of isothermal incompressible and inviscid non--conducting liquid jets in a uniform magnetic field, is considered. The equivalence between static and dynamic approaches at the onset of instability and cut--off wavelength is shown. It is established that in the absence of electric currents the stability of permeable jets can be changed by the magnetic field. A new dispersion relation for magnetocapillary instability in such jets is derived. This relation differs from that given by Chandrasekhar. The existence of critical magnetic field which stabilizes jets with finite susceptibility is established. It is shown that the jet is stabilized by the field irrespective of its being para-- or diamagnetic, but the extent of stabilization is different.