  Self-organization in an unmagnetized collisionless plasma (in this paper)
refers to formation of transient coherent structures such as collective
oscillations (electrostatic waves) or magnetic fields resulting from so-called
kinetic effects in the plasma. This topical review provides a comprehensive
analysis of the self-organization of strong-field photoionized, non-equilibrium
plasmas through kinetic instabilities. The authors propose and demonstrate a
novel experimental platform that enables the formation of dense plasmas with
known highly anisotropic and nonthermal electron velocity distribution
functions on a timescale on the order of an inverse electron plasma frequency.
We then show that such plasmas are highly susceptible to a hierarchy of kinetic
instabilities, including two-stream, current filamentation and Weibel, that
convert a fraction of the electron kinetic energy into electric and/or magnetic
energy stored in self-organized structures. The electrostatic waves so produced
are measured using a collective light (Thomson) scattering technique with
femtosecond resolution as the kinetic instabilities aided by collisions
eventually thermalize the plasma electrons. In addition, we describe a novel
experimental technique that has made it possible to map the temporal evolution
of the wavenumber spectrum of the thermal Weibel instability with picosecond
resolution, which leads to the formation of quasi-static coherent magnetic
fields with different topologies in photoionized plasmas. Finally, the paper
summarizes the important results and discusses future directions on this topic.
