  A great possible achievement for the MMS mission would be crossing electron
diffusion regions (EDR). EDR are regions in proximity of reconnection sites
where electrons decouple from field lines, breaking the frozen in condition.
Decades of research on reconnection have produced a widely shared map of where
EDRs are. We expect reconnection to take place around a so called x-point
formed by the intersection of the separatrices dividing inflowing from
outflowing plasma. The EDR forms around this x-point as a small electron scale
box nested inside a larger ion diffusion region. But this point of view is
based on a 2D mentality. We have recently proposed that once the problem is
considered in full 3D, secondary reconnection events can form [Lapenta et al.,
Nature Physics, 11, 690, 2015] in the outflow regions even far downstream from
the primary reconnection site. We revisit here this new idea confirming that
even using additional indicators of reconnection and even considering longer
periods and wider distances the conclusion remains true: secondary reconnection
sites form downstream of a reconnection outflow causing a sort of chain
reaction of cascading reconnection sites. If we are right, MMS will have an
interesting journey even when not crossing necessarily the primary site. The
chances are greatly increased that even if missing a primary site during an
orbit, MMS could stumble instead on one of these secondary sites.
