New aspects of wake field generation in plasmas

We consider various properties of wake field generation in plasmas. In part icular the influence of an external magnetic field is studied. It turns out that the magnetic field makes it possible for the wake field to propagate out of the plasma, and thereby provide information about the electron densi ty profile. Furthermore, an example where a dust-acoustic wake field is exc ited by an ion-acoustic pulse is considered, as a means to illustrate gener al principles for wake field generation.