Super-Fermi acceleration in multiscale MHD reconnection

We investigate the Fermi acceleration of charged particles in 2D MHD anti-parallel plasmoid reconnection, finding a drastic enhancement in energization rate [Formula: see text] over a standard Fermi model of [Formula: see text]. The shrinking particle orbit width around a magnetic island due to [Formula: see text] drift produces a [Formula: see text] power law with [Formula: see text]. The increase in the maximum possible energy gain of a particle within a plasmoid due to the enhanced efficiency increases with the plasmoid size and is by multiple factors of 10 in the case of solar flares and much more for larger plasmas. Including the effects of the non-constant [Formula: see text] drift rates leads to further variation in power law indices from [Formula: see text] to [Formula: see text], decreasing with plasmoid size at the time of injection. The implications for energetic particle spectra are discussed alongside applications to 3D plasmoid reconnection and the effects of a guide field.

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