braking index دیشن ِ لگامش dišan-e legâmeš
*Fr.: indice de freinage*
A parameter indicating the rate at which a → *pulsar*
slows down. Neutron stars are powered by → *rotational energy*
and lose energy by accelerating particle → *wind*s
and by emitting → *electromagnetic radiation*.
The → *rotation frequency*, Ω, thus decreases with time
and this slowdown is usually described by the relation
Ω^{.} = - *kΩn*, where *k* is a positive constant
which depends on the → *moment of inertia*
and the → *magnetic dipole moment*
of the → *neutron star* and *n* is the braking index.
Conventionally, the braking index is derived by differentiation of the above equation,
yielding *n* = ΩΩ^{..} / Ω^{.2}.
In a highly simplified model in which the spin-down torque
arises from dipole radiation at the rotation frequency, one
expects *n* = 3 (Johnston, S., Galloway, D., 1999, arXiv:astro-ph/9905058). → *braking*; → *index*. |