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Lee Suttle (Imperial): Magnetic reconnection experiments on the Magpie pulsed power generator

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Abstract: Magnetic reconnection facilitates the break-down of the frozen-in flux condition of idealised MHD, allowing plasma and magnetic fields to decouple and field lines to reconfigure, releasing energy in the form of heat and motion. Reconnection is responsible for dramatic events such as Coronal Mass Ejections from the surface of the Sun, and plays an important role in setting the energy balance in the universe.

I will present data from experiments carried out on the MAGPIE pulsed power generator, which show the detailed structure of a reconnection current sheet, produced by the collision of two counter-streaming magnetised plasma flows.

In our quasi-2D setup [1,2], the continuous supersonic flows are produced with strongly embedded magnetic fields (ReM~50, B~2T) of opposing directions. Their interaction leads to the formation of a dense and long-lasting layer, where we observe the annihilation of the arriving magnetic flux, accompanied by an increase in plasma temperature and the fast outflow of material along the layer.

The setup allows control over the dynamic Beta parameter of the plasma, by choice of the plasma material. This also enables us to introduce radiative effects to the system, as well as entering a regime where the reconnection current sheet is instable to the tearing-mode instability and consequently we observe the formation of plasmoids.

I will discuss detailed spatially and temporally resolved measurements of the plasma parameters both upstream and inside the current sheet, using a diagnostic suite consisting of simultaneous Thomson scattering, Faraday rotation polarimetry and laser interferometry imaging. From this information, we can determine the pressure balance and energy partition during the reconnection process.

[1] L.G. Suttle et al., Phys. Rev. Lett. 116 (2016)

[2] J.D. Hare et al., Phys. Rev. Lett. 118 (2017)

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