Transient Radiation of an Electric Dipole in a Uniaxially Anisotropic Plasma

Transient radiation from an infinitesimal dipole in a uniaxial plasma medium is examined for the signal frequency Wo greater, as well as less than, the plasma frequency Wp. The propagation of the main signal is calculated along different angular directions as functions of radial distance and time. It is found that, as a consequence of the anisotropy of the medium, the geometry of the “wavefront” may deviate considerably from a spherical surface: For X =( ωp / ωo )2 < l. the signal travels further along the magnetic axis than in the direction transverse to this axis. A much more pronounced effect occurs for X > 1, as the “wavefront” becomes four leaved. These correspond to non‐overlapping regions where the signal is either strictly propagating or strictly evanescent. For a given time there is also a dark region separating these two where no signal has reached. Of particular interest is the result that the critical characteristic bicones where the fields become infinite in the steady‐state analysis always remain in the dark region. This dark region narrows to zero only in the limit of t → ∞. These results shed new light on the so‐called “infinity‐catastrophe” problem which has become a subject of much controversy in recent years. The results of the present study suggest the desirability of a more realistic model for the medium which will include finite losses.