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Benjamin Chandran (University of Iowa)
Observations of narrow radio-emitting filaments near the Galactic center have been interpreted in previous studies as evidence of a pervasive vertical (i.e. perpendicular to the Galactic plane) milliGauss magnetic field in the central 150 pc of the Galaxy. Such a magnetic field would have important implications for the central environments of spiral galaxies and would, for somewhat complex reasons, be a key piece of evidence in support of a pre-Galactic origin of the Galactic magnetic field. This poster addresses the question of whether such an intense vertical magnetic field, whose pressure significantly exceeds the thermal pressure of the surrounding medium, could be confined. A simple cylindrically symmetric model for the equilibrium in this central region is proposed in which horizontal (i.e. parallel to the Galactic plane) magnetic fields embedded in an annular band of partially ionized molecular material of radius 150 pc are wrapped around vertical magnetic fields threading hot plasma. Since orthogonal magnetic fields can not easily interpenetrate, the weight of the molecular material can prevent the vertical magnetic field from expanding. The stability of this cylindrically symmetric equilibrium is studied indirectly by analyzing the stability of an infinite isothermal slab with dense plasma suspended above low-density plasma. The slab is unstable at wavelengths much shorter than one scale height of the dense plasma when the magnetic pressure in the cloud is much greater than the thermal pressure P. This is used to argue that the cylindrical equilibrium is unstable if the magnetic pressure of the vertical field is >> P, or, equivalently, if the vertical field is >> 50 microGauss.
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The author(s) of this abstract have provided an email address for comments about the abstract: benjamin-chandran@uiowa.edu