Generation of large scale potential difference by currentless plasma jets along the mirror field

A new mechanism of producing auroral electrons is proposed. Field‐aligned plasma jets, presumably generated by magnetic reconnection in the magnetotail, give rise to charge separation along the mirror field whereby electrons are accelerated by the parallel electric field. The analysis shows that the potential difference can be expressed by eΦ=W∥ i (1‐1/γ)R/(1+R) where W∥ i is the ion parallel flow energy, γ is the mirror ratio and R is the ratio of the electron to ion temperature. In the magnetotail, W∥ i≃10keV, R≃0.2∽0.5 and γ≃10³, so that the potential drop can reach several kV which is reasonable to make auroral electrons.