Year: 2005
Type: article
Abstract: An analytical model is developed for the screening of the external magnetic field of a rotating, axisymmetric neutron star due to the accretion of plasma from a disk. The decrease of the field occurs as a result of the electric current in the infalling plasma. The deposition of this current-carrying plasma on the star's surface creates an induced magnetic moment with a sign opposite to that of the original magnetic dipole. The field decreases independent of whether the star spins up or spins down. The timescale for an appreciable decrease (factor of >100) of the field is found to be ~1.6 × 10 7 yr, for a mass accretion rate Ṁ = 10 -9 M ☉ yr -1 and an initial magnetic moment μ i = 10 30 G cm 3 , which corresponds to a surface field of 10 12 G if the star's radius is 10 6 cm. The timescale varies approximately as μ /Ṁ 1.9 . The decrease of the magnetic field does not have a simple relation to the accreted mass. Once the accretion stops the field leaks out on an Ohmic diffusion timescale that is estimated to be >10 9 yr.
Source: The Astrophysical Journal
DOI: 10.1086/429532
Authors: R. V. E. Lovelace, M. M. Romanova, G. S. Bisnovatyi‐Kogan
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2119177034