Lorentz Mapping of Magnetic Fields in Hot Dense Plasmas

Petrasso, R. D.; Li, C. K.; Séguin, F. H.; Rygg, J. R.; Frenje, J. A.; Betti, R.; Knauer, J.P.; Meyerhofer, D. D.; Amendt, P. A.; Froula, D. H.; Landen, O. L.; Patel, P. K.; Ross, J. S.; Town, R. P. J.

doi:10.1103/physrevlett.103.085001

Cited by 53 publications

(39 citation statements)

References 29 publications

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“…The proton radiography data show magnetic fields not where they were previously thought to be. Previous work showed magnetic fields at the surface of a solid target concentrated on a hemispherical shell surrounding the laserablated plasma (or, 'bubble'), with the maximum field amplitude near the bubble edge, falling to zero at its cen- ter [28][29][30][31]. The data reported here show magnetic fields concentrated at the edge of the laser-focal region, well within the expanding coronal plasma.…”

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confidence: 51%

Precision Mapping of Laser-Driven Magnetic Fields and Their Evolution in High-Energy-Density Plasmas

et al. 2015

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supporting

confidence: 51%

Precision Mapping of Laser-Driven Magnetic Fields and Their Evolution in High-Energy-Density Plasmas

et al. 2015

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“…1c, each experiment involved two 500-J beams of 351-nm laser light striking a 5-mm-thick CH foil for 1 ns and focused into 800-mm spots separated by 1.4 mm. The interaction of each laser beam with the foil produced an expanding, hemispherical plasma bubble with an azimuthal 0.5 MG magnetic field concentrated at its perimeter 16 , where the plasma b was around 10. Unlike previous investigations of reconnection in symmetric laser-produced plasma configurations [17][18][19] , these experiments additionally introduced a delay (Dt) between the two beams incident on the foil.…”

Section: Laser-driven Asymmetric Magnetic Reconnection Experimentsmentioning

confidence: 99%

A laboratory study of asymmetric magnetic reconnection in strongly driven plasmas

Rosenberg

Fox

et al. 2015

Nat Commun

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Magnetic reconnection, the annihilation and rearrangement of magnetic fields in a plasma, is a universal phenomenon that frequently occurs when plasmas carrying oppositely directed field lines collide. In most natural circumstances, the collision is asymmetric (the two plasmas having different properties), but laboratory research to date has been limited to symmetric configurations. In addition, the regime of strongly driven magnetic reconnection, where the ram pressure of the plasma dominates the magnetic pressure, as in several astrophysical environments, has also received little experimental attention. Thus, we have designed the experiments to probe reconnection in asymmetric, strongly driven, laser-generated plasmas. Here we show that, in this strongly driven system, the rate of magnetic flux annihilation is dictated by the relative flow velocities of the opposing plasmas and is insensitive to initial asymmetries. In addition, out-of-plane magnetic fields that arise from asymmetries in the three-dimensional plasma geometry have minimal impact on the reconnection rate, due to the strong flows.

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“…1, a 12-μm-thick CH foil (1:1 atomic proportion at a density of 1.11 g=cm 3 ) was irradiated by two 930-J, 1-ns laser pulses at a wavelength of 351 nm and with an 800-μm spot size. The laser spots were separated on the foil by 1.4 mm, each producing an expanding, hemispherical plasma bubble with an azimuthal magnetic field concentrated at its perimeter [26]. These plasmas expanded into each other, forcing their oppositely directed magnetic fields to interact and reconnect.…”

mentioning

confidence: 99%

Slowing of Magnetic Reconnection Concurrent with Weakening Plasma Inflows and Increasing Collisionality in Strongly Driven Laser-Plasma Experiments

Rosenberg

Fox

et al. 2015

Phys. Rev. Lett.

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An evolution of magnetic reconnection behavior, from fast jets to the slowing of reconnection and the establishment of a stable current sheet, has been observed in strongly driven, β ≲ 20 laser-produced plasma experiments. This process has been inferred to occur alongside a slowing of plasma inflows carrying the oppositely directed magnetic fields as well as the evolution of plasma conditions from collisionless to collisional. High-resolution proton radiography has revealed unprecedented detail of the forced interaction of magnetic fields and super-Alfvénic electron jets (V jet ∼ 20V A ) ejected from the reconnection region, indicating that two-fluid or collisionless magnetic reconnection occurs early in time. The absence of jets and the persistence of strong, stable magnetic fields at late times indicates that the reconnection process slows down, while plasma flows stagnate and plasma conditions evolve to a cooler, denser, more collisional state. These results demonstrate that powerful initial plasma flows are not sufficient to force a complete reconnection of magnetic fields, even in the strongly driven regime. [4] plasmas, where oppositely directed magnetic fields undergo a modification of field-line topology and release magnetic energy. While reconnection has typically been studied experimentally in tenuous, quasi-steady-state plasmas, reconnection of magnetic fields in strongly driven (ram pressure > magnetic pressure), β > 1 (total thermal pressure > magnetic pressure) plasmas occurs frequently in astrophysics, impacting dynamics of plasmas in the solar photosphere [5] and at the heliopause [6]. In these strongly driven environments, the rate of reconnection is dictated largely by hydrodynamics and the plasma flows that advect the magnetic fields.In addition, when the scale width of the reconnection region is smaller than the ion inertial length (d i ≡ c=ω pi ), electrons and ions decouple, and the reconnection process is governed by electron flows, rather than by the entire plasma fluid. This two-fluid reconnection (otherwise known as Hall reconnection or collisionless reconnection) is faster than classical Sweet-Parker [7,8] reconnection in the collisional, single-fluid regime. Two-fluid reconnection is a common occurrence in astrophysics [9], and it has been studied in tenuous, quasisteady plasma experiments [10,11]. Two-fluid reconnection in the high β or strongly driven regimes is especially pertinent at the dayside magnetopause of the Earth and other planets [12,13], though, to date, there has been little laboratory investigation of the physics of two-fluid reconnection in such plasmas.This Letter presents the direct observation of two-fluid reconnection features-fast electron jets-preceding the stagnation of magnetic fields and the establishment of a stable current sheet in a strongly driven, β ≲ 20 plasma experiment. These experiments were conducted using laser-produced plasmas, a well-established platform for studies of high-β magnetic reconnection. Prior experiments have examined the annihilatio...

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Lorentz Mapping of Magnetic Fields in Hot Dense Plasmas

Cited by 53 publications

References 29 publications

Precision Mapping of Laser-Driven Magnetic Fields and Their Evolution in High-Energy-Density Plasmas

Precision Mapping of Laser-Driven Magnetic Fields and Their Evolution in High-Energy-Density Plasmas

A laboratory study of asymmetric magnetic reconnection in strongly driven plasmas

Slowing of Magnetic Reconnection Concurrent with Weakening Plasma Inflows and Increasing Collisionality in Strongly Driven Laser-Plasma Experiments

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