title: Direct observation of turbulent magnetic fields in hot, dense laser produced plasmas.
abstract: Turbulence in fluids is a ubiquitous, fascinating, and complex natural phenomenon that is not yet fully understood. Unraveling turbulence in high density, high temperature plasmas is an even bigger challenge because of the importance of electromagnetic forces and the typically violent environments. Fascinating and novel behavior of hot dense matter has so far been only indirectly inferred because of the enormous difficulties of making observations on such matter. Here, we present direct evidence of turbulence in giant magnetic fields created in an overdense, hot plasma by relativistic intensity (10(18) W/cm(2)) femtosecond laser pulses. We have obtained magneto-optic polarigrams at femtosecond time intervals, simultaneously with micrometer spatial resolution. The spatial profiles of the magnetic field show randomness and their k spectra exhibit a power law along with certain well defined peaks at scales shorter than skin depth. Detailed two-dimensional particle-in-cell simulations delineate the underlying interaction between forward currents of relativistic energy "hot" electrons created by the laser pulse and "cold" return currents of thermal electrons induced in the target. Our results are not only fundamentally interesting but should also arouse interest on the role of magnetic turbulence induced resistivity in the context of fast ignition of laser fusion, and the possibility of experimentally simulating such structures with respect to the sun and other stellar environments.
authors.affiliation: Tata Institute of Fundamental Research, 1-Homi Bhabha Road, Mumbai 400005, India.
authors.forename: Sudipta
authors.initials: S
authors.lastname: Mondal
authors.forename: V
authors.initials: V
authors.lastname: Narayanan
authors.forename: Wen Jun
authors.initials: WJ
authors.lastname: Ding
authors.forename: Amit D
authors.initials: AD
authors.lastname: Lad
authors.forename: Biao
authors.initials: B
authors.lastname: Hao
authors.forename: Saima
authors.initials: S
authors.lastname: Ahmad
authors.forename: Wei Min
authors.initials: WM
authors.lastname: Wang
authors.forename: Zheng Ming
authors.initials: ZM
authors.lastname: Sheng
authors.forename: Sudip
authors.initials: S
authors.lastname: Sengupta
authors.forename: Predhiman
authors.initials: P
authors.lastname: Kaw
authors.forename: Amita
authors.initials: A
authors.lastname: Das
authors.forename: G Ravindra
authors.initials: GR
authors.lastname: Kumar
mesh_terms: D055580:Astronomical Phenomena; D003198:Computer Simulation; D006358:Hot Temperature; D007834:Lasers; D060526:Magnetic Fields; D008962:Models, Theoretical; D016082:Solar System