The Disk-Halo Transition of the Milky Way Magnetic Field

Abstract

For this work I used new observations from the Southern Latitude Extension (SLE), which complements the Northern Latitude Extension (NLE) of the Canadian Galactic Plane Survey (CGPS) to study the magnetic field transition from the disk to the halo of the Milky Way Galaxy. From these data, I determined 136 reliable RMs for compact extragalactic sources. I combined these data with 549 previously observed RMs from the CGPS and NLE in the same longitude region as the SLE. Using these RM data, I did some modelling to determine that the most plausible field configuration in the halo region North and South of the Galactic disk is a counter-clockwise azimuthal field, which is directed opposite to the clockwise field of the disk (as viewed from the North Galactic pole). Furthermore, the strength of field in the Southern halo seems to be half the value of the field estimated in the Northern halo. This may be the result of a localized feature known as ‘Region A’ which coincides with my observation region. Finally, and perhaps most significantly, there appears to be no evidence for a warp in either the magnetic field or the electron density, despite the presence of a warp in the observed neutral gas at the same longitudes. This suggests the possibility of a species separation at the edge of the Galaxy where the neutrals experience a warp, but the charged particles do not