What does "marginality" mean in the context of magnetically confined plasmas? I am reading the paper-Self-organized criticality and the dynamics
of near-marginal turbulent transport in
magnetically confined fusion plasmas by Sanchez and Newman.
Here, the term "marginality" is central to what they are talking about. I cannot tell if this term is within the standard magnetically confined plasma jargon, or if it exists in self-organized criticality.
A sentence from the paper - "Ultimately, the relevance of SOC ideas in the context of
MCF toroidal plasmas will depend on whether near-marginal
regimes are relevant to reactor operation or not"
What does "marginal" mean in this context? Google has been unhelpful, and the paper assumes a prior knowledge of the definition.
 A: In the abstract of Sanchez and Newman [2015], they state that:

By near-marginal it is meant that the plasma profiles might wander around the local critical thresholds for the onset of instabilities.

So what they are referring to here is something called marginal stability.  That is, the plasma will have some free energy available but not enough to excite instabilities of sufficient magnitude to disrupt the confinement of the system (i.e., instabilities tend to make the plasma hit the walls of the device or diffuse accross magnetic field lines thus reducing density in regions where you want high density).
I think the point is that they are pushing the community to stop trying to completely suppress instabilities but rather just accept that the system will always be marginally unstable and we need to learn to live within that reality (I quickly glanced at the article so take this interpretation with a grain of salt).
References

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*Sanchez, R., and D.E. Newman "Self-organized criticality and the dynamics of near-marginal turbulent transport in magnetically confined fusion plasmas," Plasma Phys. Control. Fusion 57(12), pp. 123002, doi:10.1088/0741-3335/57/12/123002, 1998.

