Explosive reconnection in magnetars
Abstract
The X-ray activity of anomalous X-ray pulsars and soft γ-ray repeaters may result from the heating of their magnetic corona by direct currents dissipated by magnetic reconnection. We investigate the possibility that X-ray flares and bursts observed from anomalous X-ray pulsars and soft γ-ray repeaters result from magnetospheric reconnection events initiated by development of the tearing mode in magnetically dominated relativistic plasma. We formulate equations of resistive force-free electrodynamics, discuss the relation of the latter to ideal electrodynamics, and give examples of both ideal and resistive equilibria. Resistive force-free current layers are unstable towards the development of small-scale current sheets where resistive effects become important. Thin current sheets are found to be unstable due to the development of the resistive force-free tearing mode. The growth rate of the tearing mode is intermediate between the short Alfvén time-scale τA and a long resistive time-scale τR: Γ~ 1/(τRτA)1/2, similar to the case of non-relativistic non-force-free plasma. We propose that growth of the tearing mode is related to the typical rise time of flares, ~10 ms. Finally, we discuss how reconnection may explain other magnetar phenomena and ways to test the model.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2003
- DOI:
- 10.1046/j.1365-2966.2003.07110.x
- arXiv:
- arXiv:astro-ph/0303384
- Bibcode:
- 2003MNRAS.346..540L
- Keywords:
-
- magnetic fields;
- plasmas;
- pulsars: general;
- Astrophysics
- E-Print:
- 27 pages, 3 figures, submitted to MNRAS