Asymptotically Self-Similar Propagation of Spherical Ionization Waves

It is shown that a new type of self-similar spherical ionization waves may exist in gases. All the spatial scales and the propagation velocity of such waves increase exponentially with time. The conditions for existence of these waves are established, their structure is described, and approximate analytical relationships between the principal parameters are obtained. It is notable that spherical ionization waves can serve as the simplest, but structurally complete and physically transparent model of a streamer in a homogeneous electric field.