Evidence of non-thermal ions in a collisional, super-Alfvenic magnetic reconnection experiment diagnosed with Thomson scattering

Magnetic reconnection is a fundamental plasma physics process, which is potentially linked to the non-thermal acceleration of particles in explosive space and astrophysical events.

In this talk we present data from experiments carried out on the MAGPIE magnetic reconnection platform at Imperial College London, which can be interpreted as evidence for non-thermal ions accelerated in the reconnection layer.

Collective optical Thomson scattering (TS) was performed across the reconnection layer formed by the collision of super-Alfvenic outflows from two inverse wire arrays. The diagnostic setup provided spatially resolved measurements of the TS ion acoustic wave (IAW) spectra at several positions across the layer and inflowing plasma.

We find that the intensity profile of the TS spectra do not follow the expected scaling for thermally driven IAWs when the TS vector is aligned with the direction of the electric field. There is a strong enhancement of the scattered signal inside the layer which is not consistent with ion acoustic turbulence, and can neither be explained by effects of the magnetic field or particle collisions on the spectra. Analysis suggests that the observed signal is consistent with a non-thermal ion population within the reconnection layer.