A GLOBAL-MODEL OF PROTOSTELLAR BIPOLAR OUTFLOW .1.

This paper presents a relatively realistic model for bipolar outflow f rom the region surrounding a point-mass core in a molecular cloud, bas ed on the idea of steady quadrupolar circulation that was suggested pr eviously, We include here compressibility and 'central heating' in add ition to the pressure centrifugal and magnetic effects included in the earlier 'cored apple' models. This heating is necessary in order to o btain a high-velocity outflow along the field lines, and especially in order to create a light low-mass 'jet' outflow along the axis of a th ick disc, which in turn forms an integral part of a more massive, lowe r velocity circulation. Although it is possible to include Poynting fl ux driving of the outflow in our models, we proceed first to study exh austively the cases where it is absent. In part I of this series we gi ve a discussion of the dynamics of solutions that possess realistic ph ysical parameters. These solutions are used in Paper II to create synt hetic line profiles and radio maps of these solutions in typically opt ically thin molecular lines, which allow direct comparison with the ob servations. This seems to be the first time that a model has been put to such a test, The required central heating may be radiative (for hig h-luminosity sources) or dissipative owing to an anomalous viscosity a nd resistivity (which permits magnetic reconnection).