# Formation of Semi-relativisitc Jets from Magnetospheres of Accreting Neutron Stars: Injection of Hot Bubbles into a Magnetic Tower

**Authors:** Yoshiaki Kato, Mitsuru Hayashi, Ryoji Matsumoto  
**arXiv:** [astro-ph/0308437](https://arxiv.org/abs/astro-ph/0308437)  
**Date:** 2003-08-25  
**Summary page:** https://www.summarizepaper.com/en/paper/astro-ph--0308437v2/

## Key points

- The paper explores the magnetic interaction between a weakly magnetized neutron star and its accretion disk.
- General relativistic effects are simulated using the pseudo-Newtonian potential.
- Well-collimated jets traveling along the rotation axis of the disk are formed by a specific mechanism involving twisted magnetic loops, twist injection from the disk, expanding magnetic loops creating a magnetic tower, and intermittent injection of hot bubbles into this tower through magnetic reconnection.
- Hot bubbles moving inside this tower catch up with working surfaces of these jets and create high energy electrons responsible for radio emission observed in Sco X-1.
- The model can explain narrow jet formation from weakly magnetized neutron stars as well as correlation between radio flares observed in both core and lobe regions in Sco X-1.

## Summary

In their paper "Formation of Semi-relativistic Jets from Magnetospheres of Accreting Neutron Stars: Injection of Hot Bubbles into a Magnetic Tower," Yoshiaki Kato, Mitsuru Hayashi, and Ryoji Matsumoto present the results of 2.5-dimensional resistive magnetohydrodynamic (MHD) simulations that explore the magnetic interaction between a weakly magnetized neutron star and its accretion disk. The authors simulate general relativistic effects using the pseudo-Newtonian potential and find that well-collimated jets traveling along the rotation axis of the disk are formed by a specific mechanism. First, magnetic loops connecting the neutron star and the disk become twisted due to differential rotation between them. Second, twist injection from the disk initiates expansion of these loops. Third, expanding magnetic loops create a magnetic tower in which accelerated disk material travels as collimated bipolar jets with a propagation speed of approximately 10% of the speed of light ($\sim 0.1c$). Fourth, intermittent injection of hot bubbles into this tower takes place through magnetic reconnection inside expanding magnetic loops at an ejection speed roughly equal to the local Alfvén speed at launch point or $\sim 0.2c$ in their simulations. Finally, hot bubbles moving inside this tower catch up with working surfaces of these jets and create high energy electrons which could be responsible for radio emission observed in Sco X-1. The authors suggest that their model can explain narrow jet formation from weakly magnetized ($|{\boldmath$B_{*}$}|\le 10^{9}$ gauss) neutron stars as well as correlation between radio flares observed in both core and lobe regions in Sco X-1. Overall, their findings provide new insights into how semi-relativistic jets form from accreting neutron stars through complex interactions between magnetic fields and accretion disks.