Speaker
Description
See full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P4.4008.pdf
Random motions of particles have an interesting property to break the magnetic field lines, and can induce a net transport flow crossing the field lines. The transport flow deserves special attention from the dynamo-theoretical point of view. By definition, the cross field diffusion velocity describes a relative one to the field line, and has a capability to generate a magnetic field in nearly frozen-in plasmas[1,2], accompanying a net change of the magnetic flux[3]. It turns out that classical diffusion due to the short range ion-electron can give rise to the magnetic change comparable to the resistive diffusion, whereas, for example, the Bohm type anomalous diffusion due to the drift turbulence can give rise to a much higher magnetic field amplification[4,5]. This dynamo mechanism by the transport flow is quite different from the conventional mean-field dynamo theory, which is based on average coupling of turbulent velocity and magnetic fluctuations [6]. The magnetic amplification by a transport flow can only be effective in a non-uniform plasma. To sustain such a flow, this mechanism requires a source and a sink. Ionization and recombination of atoms or molecules can play such roles to maintain the density profile, going through the recycling processes. In fact, in a fusion machine, recycling processes of neutrals have been known to be essential to sustain the particle confinement times[7]. In this paper, the possibility and implications of the magnetic field generation by the transport flows induced by turbulence are discussed in the context of laboratory astrophysics.
[1] T .G. Cowling, Magnetohydrodynamics, Chap5, p86, Adam Hilgar, Bristol (1976).
[2] H. Bondi and T. Gold, "On the generation of magnetism", Month.,Not. R. Soc. 110, 607 (1950).
[3] C.-M. Ryu and M. Yu, Phys. Scr. 57(5),"Magnetic field enhanced by diffusive flow", 601 (1998).
[4] T.-Y.Lee and C.-M. Ryu, "Amplification of axially symmetric magnetic field by Bohm particle diffusion", Phys. Plasmas 11, 5462 (2004),
[5] T.-Y. Lee, and C.-M. Ryu, J. Phys. D: App Phys. 40, "Magnetic field induction by Bohm plasma diffusion", (19), 5912 (2007).
[6] A. Brandenburg, "Advances in mean-field dynamo theory and applications to astrophysical turbulence ", J. Plasma Phys. 84(4) , 735840404 (2018).
[7] E. S. Marmar,"Recycling processes in tokamaks", J. Nucl. Mater. 59, 450 (1078).
