Volume 448, Number 2, March III 2006
|Page(s)||L33 - L36|
|Published online||24 February 2006|
Letter to the Editor
Galactic dynamo and helicity losses through fountain flow
School of Mathematics and Statistics, University of Newcastle, Newcastle upon Tyne, NE1 7RU, UK e-mail: firstname.lastname@example.org
2 Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007, India
3 Department of Physics, Moscow University, 119992 Moscow, Russia
4 Nordita, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark
Accepted: 19 January 2006
Aims. Nonlinear behaviour of galactic dynamos is studied, allowing for magnetic helicity removal by the galactic fountain flow.Methods. A suitable advection speed is estimated, and a one-dimensional mean-field dynamo model with dynamic α-effect is explored. Results. It is shown that the galactic fountain flow is efficient in removing magnetic helicity from galactic discs. This alleviates the constraint on the galactic mean-field dynamo resulting from magnetic helicity conservation and thereby allows the mean magnetic field to saturate at a strength comparable to equipartition with the turbulent kinetic energy.
© ESO, 2006
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