RT Journal Article T1 Ball lightning as a force-free magnetic knot A1 Fernández-Rañada, Antonio AB The stability of fireballs in a recent model of ball lightning is studied. It is shown that the balls shine while relaxing in:in almost quiescent expansion, and that three effects contribute to their stability: (i) the formation in each one during a process of Taylor relaxation of a force-free magnetic field, a concept introduced in 1954 in order to explain the existence of large magnetic fields and currents in stable configurations of astrophysical plas,nas; (ii) the so called Alfven conditions in magnetohydrodynamics; and (iii) the approximate conservation of the helicity integral. The force-free fields that appear are termed "knots" because their magnetic lines are closed and linked. PB American Physical Soc. SN 1063-651X YR 2000 FD 2000-11 LK https://hdl.handle.net/20.500.14352/58974 UL https://hdl.handle.net/20.500.14352/58974 LA eng NO [1] S. Singer, The Nature of Ball Lightning, Plenum Press, New York, 1971.[2] J.D. Barry, Ball and Bead Lightning, Plenum Press, New York, 1980.[3] M.A. Uman, Lightning, Dover, New York, 1984.[4] The Science of Ball Lightning, edited by Y.H. Ohtsuki, World Scientific, Singapore, 1989.[5] M. Stenhoff, Ball Lightning. An Unsolved Problem in Atmospheric Physics, Kluwer, Dordrecht, 1999.[6] Proceedings of the 6th International Symposium on Ball Lightning (ISBL99), edited by G. C. Dijkhuis, University of Antwerp, Antwerp, 1999.[7] Balls of Fire, Recent Research in Ball Lightning, edited by S. Singer, Springer Verlag, Berlin, in press.[8] A.F. Rañada and J.L. Trueba, Nature, London, 383, 32, 1996.[9] A.F. Rañada, M. Soler, and J.L. Trueba, J. Geophys. Res., 103, 23, 309, 1998.[10] K. Lust and A. Schlute, Z. Astrophys., 34, 263,1954.[11] I. Alexeff and M. Rader, Fusion Technol., 27, 271, 1995.[12] A.F. Rañada, J. Phys. A, 23, L815, 1990.[13] A.F. Rañada, Lett. Math. Phys., 18, 97, 1989. --- A.F. Rañada, J. Phys. A, 25, 1621, 1992.[14] A.F. Rañada and J.L. Trueba, Phys. Lett., 202A, 337 1995; 232A, 25, 1997.[15] H.K. Moffatt, J. Fluid Mech., 35, 117, 1969.[16] A.F. Rañada, Eur. J. Phys., 13, 70, 1992.[17] C.L. Rousculp and R.L. Stenzel, Phys. Rev. Lett., 79, 837, 1997.[18] R.L. Ricca, D.C. Samuels, and C.F. Barenghi, J. Fluid Mech., 391, 29, 1999.[19] G. Marsh, Force Free Magnetic Fields: Solutions, Topology and Applications, World Scientific, Singapore, 1996.[20] S. Chandrasekhar and L. Woltjer, Proc. Natl. Acad. Sci. U.S.A., 44, 285, 1958; L. Woltjer, ibid. 44, 489, 1958.[21] D. Voslamber and D.K. Callebaut, Phys. Rev., 128, 2016, 1962.[22] D.K. Callebaut, private communication.[23] J.B. Taylor, Rev. Mod. Phys., 58, 741, 1986.[24] D.L. Evans and R.S. Tankin, Phys. Fluids, 10, 1137, 1967.[25] H. Raether, Z. Phys., 112, 464, 1939.[26] I. Gallimberti, Pure Appl. Chem., 60, 663, 1988.[27] B.M. Smirnov, Phys. Rep., 188, 1, 1990.[28] Y.H. Ohtsuki and H. Ofuruton, Nature, London, 350, 139, 1991. NO © 2000 The American Physical Society. We are grateful to M. V. Berry, F. Blanco, D. Bouwmeester, D. K. Callebaut, A. Ibort, J. M. Montesinos, S. Singer, A. Tiemblo, and T. Tuomi for suggestions and encouragement. DS Docta Complutense RD 27 abr 2024