## 3. Governing equationsIn the context of the magnetospheres of YSO as protostellar class I objects and T-Tauri stars one has to deal with partially ionized dusty magnetoplasmas characterized by a dynamical rather than static dust component that plays an outstanding role for the overall dynamics. We consider a frame comoving with the neutral component (). Thus, the relevant fluid balance equations (cf. Birk et al. 1996, Shukla et al. 1997 for slightly different approximations) that describe the low-frequency (with respect to the dust gyro-frequency) dynamics of such multispecies quasineutral plasmas in ionization equilibrium are the continuity equations of the charged components (electrons, ions and dust): where and are the
mass density and the fluid velocity and the indices where where , where is the electric field and with the constant collisional resistivity which may alternatively be replaced by a turbulent resistivity caused by microinstabilities. In deriving Eq. (5) we have used Faraday's law where is the dust charge number. Additionally, we assumed that the dynamical friction is dominated by dust-neutral collisions, i.e. we are dealing with a plasma where the dust component is important for the overall dynamics rather than only an impurity effect. © European Southern Observatory (ESO) 1998 Online publication: January 27, 1998 |