The non-linear galactic dynamo. II. Oscillatory versus steady solutions.

Details The non-linear galactic dynamo. II. Oscillatory versus steady solutions. The non-linear galactic dynamo. II. Oscillatory versus steady solutions.

Feb 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996a%26a...306..740e&link_type=abstract

Astronomy and Astrophysics, v.306, p.740

Astronomy and Astrophysics

Astrophysics

16

Magnetohydrodynamics (Mhd), Turbulence, Ism: Magnetic Fields, Galaxies: Ism, Magnetic Fields

Scientific paper

In order to compute the turbulent electromotive force, the vertical momentum equation for the galactic gas is solved. The only input is the density profile of the gaseous disk. The resulting α-effect, the advection terms as well as the eddy diffusivity tensor are quenched by the feedback of the magnetic field. The only free parameters are the factor γ in the vertical structure equation and a "mixing-time" factor ctau_ for the correlation time relation. The mean-field dynamo equation is solved with a 2D time-stepping code for a flow system with the turbulence and a given galactic rotation (Elstner et al. 1990). The free parameter ctau_ strongly influences the characteristics of the resulting magnetic field. Short correlation times provide steady quadrupoles while longer correlation times provide oscillating dipoles. Only the latter yield the observed magnitude of the (negative) pitch angle. The magnetic field energy is in strict balance with the turbulence energy ("equipartition"). If -- as it must be -- the magnetic feedback also concerns the eddy diffusivity tensor, only the oscillating solutions remain realistic. The non-oscillating modes diverge. Now the fields are in slight super-equipartition and the pitch angles are reduced. The oscillation periods are of order of 1Gyr, very similar to the overall growth times.

Affiliated with

Also associated with

No associations

Rating

The non-linear galactic dynamo. II. Oscillatory versus steady solutions. does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The non-linear galactic dynamo. II. Oscillatory versus steady solutions., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The non-linear galactic dynamo. II. Oscillatory versus steady solutions. will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1153358