Issue |
A&A
Volume 440, Number 1, September II 2005
|
|
---|---|---|
Page(s) | 199 - 205 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20042098 | |
Published online | 19 August 2005 |
Protoneutron star dynamos and pulsar magnetism
1
INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy e-mail: alfio@ct.astro.it
2
INFN, Sezione di Catania, via S. Sofia 72, 95123 Catania, Italy
3
A.F. Ioffe Institute of Physics and Technology, St. Petersburg, Russia
4
Isaac Newton Institute of Chile, Branch in St. Petersburg, 194021 St. Petersburg, Russia
Received:
30
September
2004
Accepted:
26
March
2005
We have investigated the turbulent mean-field dynamo action in
protoneutron stars that are subject to convective and neutron
finger instabilities during the early evolutionary phase. While
the first one develops mostly in the inner regions of the star,
the second one is favored in the outer regions, where the
Rossby number is much smaller and a mean-field dynamo action is
more efficient. By solving the mean-field induction equation we
have computed the critical spin period below which no dynamo
action is possible and found it to be ~1 s for a wide
range of stellar models and for both axisymmetric and
non-axisymmetric magnetic fields. Because this critical period
is substantially longer than the characteristic spin period of
very young pulsars, we expect that a mean-field dynamo will be
effective for most protoneutron stars. The saturation dipole
field estimated by making use of the model of “global”
quenching fits well the pulsar magnetic fields inferred from
the spin-down data. Apart from the large-scale magnetic field,
our model also predicts a generation of small-scale fields
which are typically stronger than the poloidal field and can
survive during the lifetime of pulsars. Extremely rapidly rotating
protoneutron stars ( ms) may have a dipole field ~
1014 G.
Key words: magnetohydrodynamics (MHD) / pulsars: general / stars: neutron / stars: magnetic fields
© ESO, 2005
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