Laboratory observation of plasmoid-dominated magnetic reconnection in hybrid collisional-collisionless regime

Magnetic reconnection drives the ejection of plasmas during solar flares through changes in the magnetic fields. Here, the authors use a laboratory-based experiment to create magnetic reconnection in a regime in which the plasma on one side of the reconnection is in a strongly collisional state, while it is weakly-collisional or collisionless on the other. Magnetic reconnection, breaking and reorganization of magnetic field topology, is a fundamental process for rapid release of magnetic energy into plasmas that occurs pervasively throughout the universe. In natural circumstances, the plasma properties on either side of the reconnection layer are almost asymmetric, in particular for the collision rates that critically determine the underlying reconnection mechanism. To date, all laboratory experiments on magnetic reconnections have been limited to purely collisional or collisionless regimes. Here, we report a well-designed experimental investigation on magnetic reconnections in a hybrid collisional-collisionless regime by interactions between laser-ablated copper and plastic plasmas. We directly observe the topology evolutions of the whole process of this asymmetric magnetic reconnection by highly-resolved proton radiography. Through this, we show that the growth rate of tearing instability in such a hybrid regime is still extremely large, resulting in rapid formation of multiple plasmoids and generation of plasmoid-dominated current sheet.

Automated summary

This laboratory-based experiment investigates asymmetric magnetic reconnections in a hybrid collisional-collisionless regime, revealing the rapid growth of tearing instability and the formation of multiple plasmoids.