Mapping the complete evolution of magnetic excitation in beam-plasma system driven by an ultra-intense, femtosecond laser

Plasmas are beset with instabilities of all types, hydrodynamic, magneto-hydrodynamic, and electromagnetic. These instabilities are complex, occur over a large range of temporal and spatial scales, are most often unmanageable, and have seriously challenged our efforts at applications, even as they have shed light on the understanding of the physics of plasmas in the laboratory and astrophysical environments. A major reason for our limited success in their containment is the lack of direct experimental information on their origins and evolution, both temporal and spatial. In plasmas produced by high-intensity, short, and ultrashort pulse lasers, our knowledge of the instability stems from the (secondary) signals they generate e.g. scattering of electromagnetic waves in the form of Raman or Brillouin scattering. Rarely, if ever, has a direct measurement been made of the instantaneous evolution of the instabilities in plasmas. In this paper, we present direct measurements of the femtosecond evolution of the electromagnetic beam-driven instability that arises from the interaction of forward and return currents in an ultrahigh-intensity laser-produced plasma on a solid target.