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Criticism of magnetic reconnection
The reconnection concept has been criticized bitterly ever since it was proposed. It suffered the biggest blow when dismissed by the respected Nobel Prize winning scientist, Hannes Alfvén, who is widely considered to be the “Father of Magnetohydrodynamics”, discoverer of the "Alfvén wave", and the author of “Alfvén’s Theorem”. This theorem, often referred to as the “frozen-in” flux theorem, states that two plasma parcels that are initially connected by a magnetic field line will continue to be connected by a common magnetic field line as they move around. A relatively recent summary of the critiques was given by Falthammar [2007], who wrote: "“The magnetic field B is a vector field defined as a function of space coordinates and time. At a fixed time, one may trace a field line away from any given point in space. But that field line has no identity, and in a time-dependent magnetic field it cannot be identified with any field line at a different time, except by one convention or another.”"Alfvén’s theorem does not state that the field line has an identity and moves with the plasma parcels, though many have found it useful to think of it that way. The theorem states only that connected fluid parcels continue to be connected by a common field line as they move. It is indeed misleading but also unnecessary to regard the field line as having an identity associated with the fluid and moving with it.

The situation is resolved by the fact that magnetic "lines of force" exert forces on a conducting fluid, which can be decomposed into a magnetic pressure force transverse to the field lines and a magnetic tension force along the field lines. Together, these are identified in MHD theory as a force proportional to the vector product of local current density and the magnetic field intensity (JxB). Thus, magnetic field lines act in a way analogous to a web of fibers permeating the conducting fluid or plasma, like those of striated muscle tissue or fiberglass. These electromagnetic forces make it both tempting and useful to think of the field lines as moving with the fluid as they exert forces on it. The tension force in particular gives rise to an intuitive analogy with elastic bands, with the magnetic lines of force acting somewhat like a slingshot that propels fluid parcels.

Reconnection involves violations of Alfvén's theorem, such that fluid parcels may become separated from other parcels to which they were once connected, and "reconnected" to other fluid parcels to which they were not formerly connected. In that process, magnetic flux is transported along with the fluid flow, so the overall magnetic topology is altered, and in general becomes time dependent. It should not be too much of a surprise that Hannes Alfvén resisted the idea whose main usefulness lies in describing how his theorem is violated at times and in places.

So perhaps "magnetic reconnection" should be called “plasma reconnection” since it is a change in magnetic topology that violates Alfvén’s theorem and reconnects plasma parcels that once were connected so that they are no longer connected, or vice versa. And yet, the connecting agent is the magnetic field, so “magnetic reconnection” is not inappropriate, either.

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