Magnetic fields in ADs Magnetic “flux tube”

Mag field characteristics Magnetic loops rise out of the plane of the disk at any angle – the global field geometry is “tangled” The field lines confine and carry plasma across the disk Reconnection and snapping of the loops releases energy into the disk atmosphere – mostly in X-rays The magnetic field also transfers angular momentum out of the disk system The footpoints of the magnetic loops are anchored in the accretion disk material. Because the disk is Keplerian and material rotates at an angular velocity which depends on the distance to the centre of the disk, the loops can become stretched and tangled if both feet do not form at the same radial distance. Eventually, differentially-rotating loops will snap and reconnect, which releases huge amounts of energy, mostly in X-rays. Plasma is trapped by the loops and confined, and transfers angular momentum out of the disk system, which further assists the material as it falls towards the compact object and is accreted.