Superposing the Magnetic Spiral Structure of the Milky Way, on the Stellar Spiral Arms—Matching the Unique Galactic Magnetic Field Reversal Zone with Two Galactic Spiral Arm Segments

Abstract

. To pinpoint the peak location of the synchrotron total intensity emission in a spiral arm, we use a map of the spiralarm locations (from the observed arm tangent). Thus In a typical spiral arm in Galactic Quadrant I, we find the peak of the synchrotron radiation to be located about 220 ±40 pc away from the inner arm edge (hot dust lane) inside the spiral arm.While most of the galactic disk has a clockwise largescale magnetic field, we make a statistical analysis to delimitate more precisely the smaller reverse annulus wiith a counterclockwise galactic magnetic field. We find an annulus width of 2.1 ±0.3 kpc (measured along the Galactic radius), located from 5.5 to 7.6 kpc from the Galactic Center). The annulus does not overlay with a single spiral arm - it encompasses segments of two different spiral arms. Using a recent delineation of the position of spiral arms, the field-reversed annulus is seen to encompass the Crux-Centaurus arm (in Galactic Quadrant IV) and the Sagittarius arm (in Galactic Quadrant I). Thus the full Sagittarius-Carina arm is composed of : (1) a Sagittarius arm (in Galactic quadrant I) with a counterclockwise magnetic field, and (2) a Carina arm (in Galactic Quadrant IV). with a clockwise magnetic field. Also the full Scutum-Crux-Centaurus arm is composed of: (1) a Scutum arm (in Galactic Quadrant I) with a clockwise magnetic field, and (2) a Crux-Centaurus arm (in Galactic Quadrant IV) with a counterclockwise magnetic field.