The interaction of solar wind with a dipole magnetic field is modeled in a laboratory setting with a small cylindrical permanent magnet and magnetized plasma driven by intense lasers. The result shows a potential application in the understanding of Earth's magnetosphere near the pole region. Some significant features are observed in our experiments, such as magnetic reconnection and repulsion, which agree well with magnetohydrodynamics (MHD) simulation results. (C) 2014 Elsevier B.V. All rights reserved.

Turbulent magnetic reconnection is believed to occur in astrophysical plasmas, and it has been suggested to be a trigger of solar flares. It often occurs in long stretched and fragmented current sheets. Recent observations by the Parker Solar Probe, the Solar Dynamics Observatory and in situ satellite missions agree with signatures expected from turbulent reconnection. However, the underlying mechanisms, including how magnetic energy stored in the Sun's magnetic field is dissipated, remain unclear. Here we demonstrate turbulent magnetic reconnection in laser-generated plasmas created when irradiating solid targets. Turbulence is generated by strongly driven magnetic reconnection, which fragments the current sheet, and we also observe the formation of multiple magnetic islands and flux-tubes. Our findings reproduce key features of solar flare observations. Supported by kinetic simulations, we reveal the mechanism underlying the electron acceleration in turbulent magnetic reconnection, which is dominated by the parallel electric field, whereas the betatron mechanism plays a cooling role and Fermi acceleration is negligible. As the conditions in our laboratory experiments are scalable to those of astrophysical plasmas, our results are applicable to the study of solar flares. Laboratory experiments reveal the underlying mechanism of turbulent reconnection, including electron acceleration. These findings are directly relevant for studies of flares in the solar corona.

Magnetic reconnection is a process by which oppositely directed magnetic field lines passing through a plasma undergo dramatic rearrangement, converting magnetic potential into kinetic energy and heat(1,2). It is believed to play an important role in many plasma phenomena including solar flares(3,4), star formation(5) and other astrophysical events(6), laser-driven plasma jets(7-9), and fusion plasma instabilities(10). Because of the large differences of scale between laboratory and astrophysical plasmas, it is often difficult to extrapolate the reconnection phenomena studied in one environment to those observed in the other. In some cases, however, scaling laws(11) do permit reliable connections to made, such as the experimental simulation of interactions between the solar wind and the Earth's magnetosphere(12). Here we report well-scaled laboratory experiments that reproduce loop-top-like X-ray source emission by reconnection outflows interacting with a solid target. Our experiments exploit the mega-gauss-scale magnetic field generated by interaction of a high-intensity laser with a plasma to reconstruct a magnetic reconnection topology similar to that which occurs in solar flares. We also identify the separatrix and diffusion regions associated with reconnection in which ions become decoupled from electrons on a scale of the ion inertial length.