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Astron. Astrophys. 330, 1145-1148 (1998)

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The source region of the fast solar wind

J.F. McKenzie, G.V. Sukhorukova and W.I. Axford

Max-Planck-Institut für Aeronomie, Postfach 20, D-37189 Katlenburg-Lindau, Germany

Received 31 July 1997 / Accepted 16 October 1997


We discuss how the lower corona may be connected to the chromospheric network pattern through magnetic funnels at the boundaries of the chromospheric network. At the feet of these funnels are located thin ionizing layers. The steady-state flow and temperature structure in the funnels is analyzed on the basis of the continuity of downward electron heat flux from the coronal base and the upward advection of enthalpy and kinetic energy from below. The flow in such a funnel remains subsonic provided the downward heat flux from the lower corona is sufficiently large, otherwise it becomes choked or exhibits a critical supersonic-subsonic transition. The ionization layer, generated by electron impact, is very thin ([FORMULA] 20 km) and is located at about 4.5 chromospheric pressure scale heights (i.e. [FORMULA] 700 km) below the base and its structure is similar to that of a classical constant pressure weak deflagration in which the flow is accelerated but remains subsonic. Although our model may shed some light on the structure of the connection between the fast solar wind and its origin in the chromosphere it cannot, by virtue of being steady, uniquely predict the mass flux of the wind.

Key words: Sun: corona – solar wind

Send offprint requests to: J.F. McKenzie

© European Southern Observatory (ESO) 1998

Online publication: January 27, 1998