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Yoshiaki Sofue, The Galactic Center Molecular Tornado Driven by Magnetic Squeezing Mechanism, Publications of the Astronomical Society of Japan, Volume 59, Issue 1, 25 February 2007, Pages 189–198, https://doi.org/10.1093/pasj/59.1.189
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Abstract
Based on an analysis of the CO line-survey data, we report on peculiar properties of a helical-spur object of molecular gas at a radial velocity of |$V_{\rm lsr}\sim 70$|km s|$^{-1}$| extending vertically from the galactic plane at |$l = 1{\rlap{\hskip.75pt{^\circ}}\hskip.75pt.\hskip1pt} 2$| to high latitudes of |$b\sim \pm 0{\rlap{\hskip.75pt{^\circ}}\hskip.75pt.\hskip1pt} 6 $|. We call the object the Galactic Center molecular Tornado (GCT). The tornado is 170 pc (|$1{\rlap{\hskip.75pt{^\circ}}\hskip.75pt.\hskip1pt} 2$|) long and 14 pc (|$6'$|) wide, and is spinning at a rotation velocity of |$\sim 30$|km s|$^{-1}$| in the same sense as, but with much steeper velocity gradient than, the galactic rotation. The coherent collimation and helical structure suggest that the tornado is related to an ordered vertical magnetic field. We propose a magnetic squeezing mechanism such that a vertical magnetic tube or a root of a large-scale prominence-like magnetic flux is twisted and squeezed by a molecular cloud in galactic rotation, and the gas is pushed out along the magnetic tube. The angular momentum of the cloud is lost along the twisting magnetic tube, which promotes gravitational collapse of the cloud and enhances star formation.
