Nature of the α effect in magnetohydrodynamics

It is shown that the ff effect of mean-field magnetohydrodynamics, which consists in the generation of a mean electromotive force along the mean magnetic field by turbulently fluctuating parts of velocity and magnetic field, is equivalent to the simultaneous generation of both turbulent and mean-field magnetic helicities, the generation rates being equal in magnitude and opposite in sign. In the particular case of statistically stationary and homogeneous fluctuations this implies that the ff effect can increase the energy in the mean magnetic field only under the condition that also magnetic helicity is accumulated there.

Metadaten
Verfasserangaben:	Norbert Seehafer ORCiD
URN:	urn:nbn:de:kobv:517-opus-13919
Schriftenreihe (Bandnummer):	NLD Preprints (25)
Publikationstyp:	Preprint
Sprache:	Englisch
Erscheinungsjahr:	1995
Veröffentlichende Institution:	Universität Potsdam
Datum der Freischaltung:	08.06.2007
Organisationseinheiten:	Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
	Zentrale und wissenschaftliche Einrichtungen / Interdisziplinäres Zentrum für Dynamik komplexer Systeme
DDC-Klassifikation:	5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
PACS-Klassifikation:	50.00.00 PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES / 52.00.00 Physics of plasmas and electric discharges (for space plasma physics, see 94.05.-a; for astrophysical plasmas, see 95.30.Qd; for physics of the ionosphere and magnetosphere, see 94.20.-y and 94.30.-d respectively) / 52.30.-q Plasma dynamics and flow
	90.00.00 GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS (for more detailed headings, see the Geophysics Appendix) / 95.00.00 Fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations / 95.30.-k Fundamental aspects of astrophysics (see also section 26 Nuclear astrophysics) / 95.30.Qd Magnetohydrodynamics and plasmas (see also 52.30.Cv and 52.72.+v-in physics of plasmas)