HR: 12:05h
AN: SH52A-07    [Abstracts]
TI: Is the Bipolar Planetary-Nebula M2-9 Formed by Self-Consistent Magnetic Confinement?
AU: * Washimi, H
EM: haruichi.washimi@ucr.edu
AF: IGPP, University of California, University Ave., Riverside, CA 92521 United States
AU: Zank, G P
EM: zank@ucr.edu
AF: IGPP, University of California, University Ave., Riverside, CA 92521 United States
AU: Tanaka, T
EM: tatanaka@geo.kyushu-u.ac.jp
AF: Faculty of Science, Kyushu University, Hakozaki, Fukuoka, 812-8581 Japan
AU: Balick, B
EM: balick@astro.washington.edu
AF: Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98159 United States
AB: The past decade has witnessed a very detailed study of the interaction of the solar wind with the local interstellar medium. This has been a combination of theoretical and computational modeling and observations, both remote (such as Lyman-alpha absorption measurements by the Hubble telescope) and in situ (Voyager). These models have begun to be applied to other astrophysical systems interacting with their local interstellar medium, and the lessons and physics learned locally have guided our approach to these more remote systems. Some of the most spectacular astrophysical objects are planetary nebulae and we describe here one example of global heliospheric modeling applied to the beautiful planetary nebula M2-9. M2-9 is composed of three main components, namely two bright, narrow and highly axis-symmetric bipolar lobes, two faint outer flows along the bipolar lobes, and a bright compact central core. The surrounding matter seems to be much more dilute than the bipolar flow. We assume that the magnetic pressure of the toroidal field in the stellar wind plays a dominant role in forming the bipolar flow along the rotation axis, and we examine this mechanism by using global 3-D MHD simulations. We find that we can explain the M2-9 structure when the magnetic pressure in the stellar wind is comparable to the stellar-wind ram pressure. The stellar wind, which expands in the radial direction, bends poleward with distance from the star due to a magnetic pinch effect, hence the wind density at high latitudes is enhanced and bipolar lobes are formed. The material surrounding the bipolar lobes originates from middle and lower latitudes, which results in the formation of two faint outer flows. Hence the overall structure is a consequence of the stellar wind itself. This means that the stellar wind results in two kinds of self-consistent circumstellar gas distributions, one corresponding to a collimated flow and the other confines the flow as an envelope.
DE: 0466 Modeling
DE: 0500 COMPUTATIONAL GEOPHYSICS (3200, 3252, 7833)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005