<p>We present a semi-analytical model of magnetized accretion disks around neutron stars that extends previous disk-magnetosphere interaction frameworks by including Hall diffusion and disk-driven mass outflows. The modified induction and angular momentum equations are solved numerically to investigate the rotational structure of the disk. The results show that Hall diffusion significantly alters the angular momentum transport within the disk, broadening the transition region between Keplerian rotation and corotation with the neutron star. In contrast, the impact of disk outflows is twofold and critically depends on the specific angular momentum extracted from or delivered to the disk by the outflows, as parameterized by <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$l$</EquationSource> <EquationSource Format="MATHML"><math> <mi>l</mi> </math></EquationSource> </InlineEquation>. Outflows that remove angular momentum from the disk (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$l < 0$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>l</mi> <mo><</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>) reduce the fastness parameter and broaden the transition zone, while outflows that supply angular momentum to the disk (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$l > 0$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>l</mi> <mo>></mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>) increase the fastness parameter and narrow the transition zone. When both effects of Hall diffusion and outflows operate together, they establish a competitive interplay that dictates the final disk configuration. Hall diffusion tends to expand the region of sub-Keplerian rotation, while outflows can either counteract or reinforce this broadening depending on the sign and magnitude of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$l$</EquationSource> <EquationSource Format="MATHML"><math> <mi>l</mi> </math></EquationSource> </InlineEquation>. These findings highlight the importance of non-ideal MHD processes and outflows in determining the structure and dynamics of accretion disks around magnetized compact objects.</p>

Disk dynamics in X-ray pulsars with Hall diffusion and mass-loss outflows

期刊论文
发表日期：

2026年4月13日

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Kazem Faghei

摘要

We present a semi-analytical model of magnetized accretion disks around neutron stars that extends previous disk-magnetosphere interaction frameworks by including Hall diffusion and disk-driven mass outflows. The modified induction and angular momentum equations are solved numerically to investigate the rotational structure of the disk. The results show that Hall diffusion significantly alters the angular momentum transport within the disk, broadening the transition region between Keplerian rotation and corotation with the neutron star. In contrast, the impact of disk outflows is twofold and critically depends on the specific angular momentum extracted from or delivered to the disk by the outflows, as parameterized by $l$ $l$ . Outflows that remove angular momentum from the disk ( $l < 0$ $l < 0$ ) reduce the fastness parameter and broaden the transition zone, while outflows that supply angular momentum to the disk ( $l > 0$ $l > 0$ ) increase the fastness parameter and narrow the transition zone. When both effects of Hall diffusion and outflows operate together, they establish a competitive interplay that dictates the final disk configuration. Hall diffusion tends to expand the region of sub-Keplerian rotation, while outflows can either counteract or reinforce this broadening depending on the sign and magnitude of $l$ $l$ . These findings highlight the importance of non-ideal MHD processes and outflows in determining the structure and dynamics of accretion disks around magnetized compact objects.