2001ApJ...553L..35L

The Seyfert galaxy NGC 1097 has a prominent bar and a luminous circumnuclear starburst ``ring.'' Magnetic fields as revealed by nonthermal radio continuum emissions correlate well with the optical barred spiral structure on large scales, have a gross enhancement overlapping with the optical/infrared ``ring'', and show a trailing swirl around and within the ``ring.'' We propose a scenario of bar-excited long-trailing fast magnetohydrodynamic (MHD) density waves at the modified inner Lindblad resonance (mILR), physically identified with the outer rim of the ``ring.'' These sustained outgoing long waves are bounced back by the Q_M-barrier in the form of incoming short-trailing waves. The damping of these waves deposits a negative angular momentum into the magnetized circumnuclear gas disk. Thus, gas materials spiral inward, bring in frozen-in magnetic flux, and accumulate inside the mILR to create a circular zone of high density and magnetic flux vulnerable to massive star formation. Depending on the wave damping efficiency, this process may simultaneously sustain a net mass inflow across the ``ring'' and toward the nucleus. A wavelet analysis on a Hubble Space Telescope image of central NGC 1097 shows a distinct two-arm spiral structure extended down to the nucleus as a strong evidence for circumnuclear MHD density waves. We predict that magnetic field observations with improved sensitivity and resolution would eventually reveal a specific correspondence between circumnuclear optical and magnetic field spirals similar to those known to exist on large scales in nearby spiral galaxies, including NGC 1097.