Assess kinetic viability of SMAPs under parallel particle dynamics

Determine whether slow magnetoacoustic pulsations in tokamak plasmas with centrally flat safety factor q slightly above unity can survive ion parallel streaming and associated kinetic damping, including whether weak magnetic-field ergodicity permits the waves to outpace ion streaming sufficiently to maintain the thermal misbalance underlying the pulsations.

Background

The paper identifies slow magnetoacoustic pulsations (SMAPs) in a visco-resistive single-fluid MHD model with a centrally flat safety factor q greater than unity. Their existence depends on sufficiently weak thermal diffusion, which allows a thermal misbalance to persist. The authors note that kinetic parallel dynamics, particularly ion streaming and Landau damping, may eliminate this mechanism under realistic tokamak conditions.

The unresolved issue is whether SMAPs are a physical phenomenon that can occur in realistic magnetically confined plasmas or instead an artifact of the single-fluid MHD treatment. Resolving it requires kinetic simulations that include parallel particle dynamics and damping.

References

This motivates further study in kinetic models, where collisionless mechanisms for fast reversible reconnection exist and proper treatment of parallel dynamics will allow to assess the role of Landau damping as well as the question whether the ${\bm B}$ field's weak ergodicity in the $q\sim 1$ region allows the waves to outpace the ion's parallel streaming to maintain the thermal misbalance underlying SMAPs.

— Study of low-frequency core-edge coupling in a tokamak: III. Core-localized MHD continuum pulsations \& distant forced reconnection  (2609.29871 - Bierwage et al., 24 Sep 2026) in Abstract; Section 4, subsection “Feasibility of thermal misbalance”; Section 6, Conclusion

Meanwhile, we have not investigated whether entropy waves play a distinct role here.

— Study of low-frequency core-edge coupling in a tokamak: III. Core-localized MHD continuum pulsations \& distant forced reconnection  (2609.29871 - Bierwage et al., 24 Sep 2026) in Section 4, subsection “Feasibility of thermal misbalance”

It remains to be checked with kinetic models whether SMAPs that were encountered in our resistive MHD simulations have any chance of occurring under realistic MCF tokamak plasma conditions.

— Study of low-frequency core-edge coupling in a tokamak: III. Core-localized MHD continuum pulsations \& distant forced reconnection  (2609.29871 - Bierwage et al., 24 Sep 2026) in Section 6, Conclusion