Dynamos and cosmic magnetic fields

Russell Kulsrud, Steve C. Cowley, Andrei V. Gruzinov, R. N. Sudan

    Research output: Contribution to journalArticle

    Abstract

    This paper discusses the origin of the galactic magnetic field. The theory of the mean field dynamo in the interstellar medium is reviewed and shown to be flawed because it ignores the strong amplification of small-scale magnetic fields. An alternative origin is offered. It is proposed that the galactic fields are created in the protogalaxy by protogalactic turbulence. It is shown that they are first created from zero by the turbulence through the Biermann battery mechanism. The resulting weak seed fields are then amplified by the dynamo action of the protogalactic turbulence up to a field strength adequate for a primordial field origin of the galactic magnetic field. It is suggested that the amplification of the small-scale fields, that are a problem for the interstellar origin, are suppressed in the protogalaxy by collisionless processes that act on scales smaller than the mean free path. Since the relative size of the mean free path is quite large in the protogalaxy, the dynamo would generate only large-scale fields. After compression this field could become the galactic field. It is possible that no further amplification of it need occur in the interstellar medium.

    Original languageEnglish (US)
    Pages (from-to)213-226
    Number of pages14
    JournalPhysics Report
    Volume283
    Issue number1-4
    StatePublished - Apr 1997

    Fingerprint

    rotating generators
    protogalaxies
    interstellar magnetic fields
    turbulence
    magnetic fields
    mean free path
    electric batteries
    seeds
    field strength

    Keywords

    • Batteries
    • Galaxy
    • MHD dynamos
    • Protogalaxy

    ASJC Scopus subject areas

    • Physics and Astronomy(all)

    Cite this

    Kulsrud, R., Cowley, S. C., Gruzinov, A. V., & Sudan, R. N. (1997). Dynamos and cosmic magnetic fields. Physics Report, 283(1-4), 213-226.

    Dynamos and cosmic magnetic fields. / Kulsrud, Russell; Cowley, Steve C.; Gruzinov, Andrei V.; Sudan, R. N.

    In: Physics Report, Vol. 283, No. 1-4, 04.1997, p. 213-226.

    Research output: Contribution to journalArticle

    Kulsrud, R, Cowley, SC, Gruzinov, AV & Sudan, RN 1997, 'Dynamos and cosmic magnetic fields', Physics Report, vol. 283, no. 1-4, pp. 213-226.
    Kulsrud R, Cowley SC, Gruzinov AV, Sudan RN. Dynamos and cosmic magnetic fields. Physics Report. 1997 Apr;283(1-4):213-226.
    Kulsrud, Russell ; Cowley, Steve C. ; Gruzinov, Andrei V. ; Sudan, R. N. / Dynamos and cosmic magnetic fields. In: Physics Report. 1997 ; Vol. 283, No. 1-4. pp. 213-226.
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