Laser generated wake fields as a new diagnostic tool for magnetized   plasmas
  In the presence of an external magnetic field, wake fields generated by a short laser pulse can propagate out of the plasma, and thereby provide information about the electron density profile. A method for reconstructing the density profile from a measured wake field spectrum is proposed and a numerical example is given. Finally, we compare our proposal with existing plasma density diagnostic techniques. 
Martin Servin and Gert Brodin