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Astron. Astrophys. 343, 641-649 (1999)

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Field-aligned magnetohydrodynamic bow shock flows in the switch-on regime

Parameter study of the flow around a cylinder and results for the axi-symmetrical flow over a sphere

H. DeSterck  * and S. Poedts **

Center for Plasma Astrophysics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium (hans.desterck@wis.kuleuven.ac.be; stefaan.poedts@wis.kuleuven.ac.be)

Received 30 September 1998 / Accepted 6 November 1998

Abstract

A parameter study is undertaken for steady symmetrical planar field-aligned MHD bow shock flows around a perfectly conducting cylinder. For sets of values of the inflow plasma [FORMULA] and Alfvénic Mach number ([FORMULA]) which allow for switch-on shocks, a numerical solution is obtained which exhibits a complex bow shock shape and topology with multiple shock fronts and a dimpled leading front. For parameter values outside the switch-on domain, a classical single-front bow shock flow is obtained. These results show that the [FORMULA] and [FORMULA] parameter regime for which the complex bow shock topology occurs, corresponds closely to the parameter regime for which switch-on shocks are possible.

The axi-symmetrical field-aligned bow shock flow over a perfectly conducting sphere is then calculated for one set of values for [FORMULA] and [FORMULA] in the switch-on domain, resulting in a complex bow shock topology similar to the topology of the flow around a cylinder.

These complex shock shapes and topologies may be encountered in low-[FORMULA] space plasmas. Fast coronal mass ejections moving away from the sun in the low-[FORMULA] inner corona may induce preceding shock fronts with upstream parameters in the switch-on domain. Planetary and cometary bow shocks may have upstream parameters in the switch-on domain when the impinging solar wind occasionally becomes low-[FORMULA]. The simulation results may be important for phenomena in the Earth's magnetosheath.

Key words: Magnetohydrodynamics (MHD) – shock waves – methods: numerical – Sun: corona – comets: general – planets and satellites: general

* Research Assistant of the Fund for Scientific Research - Flanders (Belgium). Also at the High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO, USA
** Research Associate of the Fund for Scientific Research - Flanders (Belgium)

Send offprint requests to: H. De Sterck

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© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
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