AbstractThere is mounting evidence that the ejection of magnetic helicity from the solar surface is important for the solar dynamo. Observations suggest that in the northern hemisphere the magnetic helicity flux is negative. We propose that this magnetic helicity flux is mostly due to small scale magnetic fields; in contrast to the more systematic large scale field of the 11 year cycle, whose helicity flux may be of opposite sign, and may be excluded from the observational interpretation. Using idealized simulations of MHD turbulence as well as a simple two-scale model, we show that shedding small scale (helical) field has two important effects. (i) The strength of the large scale field reaches the observed levels. (ii) The evolution of the large scale field proceeds on time scales shorter than the resistive time scale, as would otherwise be enforced by magnetic helicity conservation. In other words, the losses ensure that the solar dynamo is always in the near-kinematic regime. This requires, however, that the ratio of small scale to large scale losses cannot be too small, for otherwise the large scale field in the near-kinematic regime will not reach the observed values.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    How magnetic helicity ejection helps large scale dynamos


    Contributors:

    Published in:

    Advances in Space Research ; 32 , 10 ; 1835-1844


    Publication date :

    2003-04-29


    Size :

    10 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English



    How Magnetic Helicity Ejection Helps Large Scale Dynamos

    Brandenburg, A. / Blackman, E. G. / Sarson, G. R. et al. | British Library Conference Proceedings | 2003


    How magnetic helicity ejection helps large scale dynamos

    Brandenburg, A. | Online Contents | 2003


    The Role of Kinetic Helicity in Spherical Shell Dynamos

    Livermore, P. W. / Hughes, D. W. / Tobias, S. M. et al. | British Library Conference Proceedings | 2006


    Strange attractor character of large-scale non-linear dynamos

    Krause, F. / Roberts, P.H. | Elsevier | 1981