Collisionless shock experiments with lasers and observation of Weibel instabilities

Abstract

Astrophysical collisionless shocks are common in the universe, occurring in supernova remnants, gamma ray bursts, and protostellar jets. They appear in colliding plasma flows when the mean free path for ion-ion collisions is much larger than the system size. It is believed that such shocks could be mediated via the electromagnetic Weibel instability in astrophysical environments without preexisting magnetic fields. Here, we present laboratory experiments using high-power lasers and investigate the dynamics of high-Mach-number collisionless shock formation in two interpenetrating plasma streams. Our recent proton-probe experiments on Omega show the characteristic filamentary structures of the Weibel instability that are electromagnetic in nature with an inferred magnetization level as high as $1% [C. M. Huntington et al., "Observation of magnetic field generation via the weibel instability in interpenetrating plasma flows," Nat. Phys. 11, 173-176 (2015)]. These results imply that electromagnetic instabilities are significant in the interaction of astrophysical conditions. V C 2015 AIP Publishing LLC. [http://dx.

Developed turbulence and nonlinear amplification of magnetic fields in laboratory and astrophysical plasmas

“…At the same time, the existence of diffuse synchrotron emission at radio wavelengths and Faraday rotation measurements indicate the presence of magnetic fields in galaxy clusters with strengths up to tens of microgausses (4,5). The standard model for the origin of these intergalactic magnetic fields is amplification of seed fields via the turbulent dynamo mechanism to the present-day observed values (6-10), but other possibilities involving plasma kinetic instabilities (11)(12)(13)(14), return currents (15,16), or primordial mechanisms (17,18) have also been invoked.…”

Collisionless electrostatic shock generation using high-energy laser systems

“…Successful generation of collisionless MHD [45,46] and ES shocks, and experimental approach to study collisionless EM shock [60][61][62]64,65] in laboratory indicate that laboratory experiment can be an alternative approach to study space and astrophysical plasma physics. Furthermore, recent achievement of mono-energetic proton acceleration by collisionless ES shock produced by ultrahigh-intensity laser system [84][85][86] shows a possibility to apply the collisionless shock to several applications including medical treatment.…”

“…We have conducted the Weibel-instability mediated collisionless EM shock experiments with Omega and Omega EP laser systems (Rochester U., U.S.A), and measured plasma parameters such as electron and ion temperatures, electron density, and flow velocity of counter-streaming plasmas [60][61][62] with collective Thomson scattering (CTS) [63], and filamentary structure produced by the Weibel instability [62,64,65] with proton radiography [66,67]. Now the NIF experiment is going on.…”

Time Evolution of Kelvin–helmholtz Vortices Associated With Collisionless Shocks in Laser-Produced Plasmas

“…Recent rapid growth of laser technologies allows us to model space and astrophysical phenomena in laboratories (Drake 1999;Remington et al 1999Remington et al , 2006Takabe et al 1999). For instance, collisionless shocks have been experimentally investigated in laser-produced counterstreaming plasmas (Morita et al 2010Kuramitsu et al 2011Kuramitsu et al , 2012Kugland et al 2012;Ross et al 2012;Fox et al 2013;Yuan et al 2013;Huntington et al 2015;Park et al 2015).W efirst reported the relatively laminar density jump with optical interferometry in collisionless counterstreaming plasmas in the absence of an external magnetic field using the Shenguang II laser facility (Morita et al 2010). In order to distinguish shock from contact surface we measured the emission jump and its time evolutions with self-emission optical pyrometry (SOP) with the Gekko XII (GXII) laser facility (Kuramitsu et al 2011).…”

“…With the OMEGA and OMEGA EP laser facilities, symmetric counterstreaming plasmas can be produced (Kugland et al 2012;Ross et al 2012). In the symmetric conditions, KHI is less effective, however, filamentation instability or Weibel instability can take place where the magnetic filaments grow in the shock transition region (Fox et al 2013;Yuan et al 2013;Huntington et al 2015;Park et al 2015). Currently verifications of collisionless shock formation due to Weibel-type instability are ongoing with the world largest laser facility, the National Ignition Facility.…”