THE MAGNETIC FIELD STRENGTH IN THE WALL OF THE LOCAL BUBBLE TOWARD l, b ≈ 300°, 0°

摘要

We present polarization measurements in the region around l, b = 300°, 0°, toward stars with well-determined distances, primarily in the range 40-200 pc. We argue that these observations trace polarization caused by dust in the wall of the Local Bubble (LB). Using a Chandrasekhar-Fermi analysis, we derive a plane-of-the-sky magnetic field strength, in the wall of the LB in this direction, of < B_⊥ > = 8_(-3)~(+5) μG, equivalent to a magnetic pressure of P_B/k ≈ 1.8 x 10~4 K cm~(-3). This pressure equals, to within the uncertainties, that in the bubble interior, as derived from EUVE observations, assuming collisional ionization equilibrium. Such a magnetic field could help us explain the observed low O VI column density associated with the LB wall.