arXiv subjects

Dominic Payne

Publications and source records attributed to Dominic Payne.

3 recordsLinked to original sources

arXiv2026

A Magnetothermodynamic Theory of Energy Transport In Collisionless Plasmas

Presented here is an exploratory conceptual framework with the aim of describing electromagnetic and thermal energy transport and transfer in collisionless plasmas in a coherent way, starting from an arrow-of-time perspective. That is, arguments about the transport of energy are fundamentally based on the idea that systems tend to fill the phase space available to them. First, we describe electric fields, magnetic fields, and plasma particles as interacting subsystems that are thermodynamically linked in specific ways. Second, we discuss the importance of the stochastic electric field in the transport of plasma particles down energy density gradients until the energy flux contributions from so-called electrothermodynamic (ETD) interactions become sufficiently uniform. Third, the logic of ETD transport is extended to a magnetized system invoking 2 types of magnetothermodyamic (MTD) transport: 1) transport of electromagnetic energy through stochastic Poynting flux and 2) plasma energy transport through stochastic drift energy fluxes associated with local ExB drift motion. The magnitudes of the ETD and MTD mechanisms are tied to local characteristic scales of the electric field fluctuations and critical scales are derived beyond which ETD mechanisms dominate MTD mechanisms. Finally, we discuss the interplay between electrothermodynamic and magnetothermodynamic equilibria (ETE and MTE), dynamics in the small critical scale (MTD) limit, and the potential relevance of this type of description to the problem of reconnection onset and scale coupling.

physics.plasm-ph↗

arXiv2026

Conversion Layer Controls the Evolution of Magnetic Deflections Near the Alfven Surface

We examine the statistics of Alfvenic deflections in both sub-Alfvenic and super-Alfvenic solar wind with particular focus on a common parameter that underlies the definition of switchbacks: the magnetic deflection angle. Our findings are in general agreement with earlier studies that suggest magnetic deflection angles > 90 degrees are very unlikely to occur in sub-Alfvenic regimes. We find that their upper limit exhibits an identifiable trend with the Alfven Mach number Ma, suggesting that gradual steepening of Alfvenic deflections with increasing Ma is a plausible mechanism controlling deflection angles in the young solar wind. Further analysis reveals that large velocity fluctuations tend to be important in the largest sub-Alfvenic magnetic deflections with increasing contributions from the parallel component very close to Ma = 1, while virtually no magnetic deflections in the super-Alfvenic regime exhibit such large velocity perturbations. We also determine the local ratio of radial Poynting flux SR to kinetic energy flux KR and find that large sub-Alfvenic deflection angles tend to be dominated by SR, while super-Alfvenic deflections are eventually dominated by the KR associated with the radial solar wind flow. Our results show that within the vicinity of the Alfven surface (where Ma = 1), there is a critical region of parameter space within which velocity deflections approach the Alfven velocity and KR/SR is close to unity. We refer to this region (where | log10(Ma)| < 0.2) as the conversion layer. The conversion layer may play a significant role in the evolution of magnetic defections by providing the medium for converting magnetic energy to particle energy and likely driving the formation of magnetic switchbacks in super-Alfvenic solar wind.

astro-ph.SR↗

arXiv2025

Thermodynamics of Shear Equilibration During Magnetic Reconnection Onset in Mixed-Equilibrium Current Sheets

Magnetic shear across the polarity inversion line (PIL) plays an important role in the explosive nature of reconnection onset and in the equilibration of current sheets, acting as a source of free energy that can enhance or inhibit the onset process under certain conditions. In this study, we use a 2D PIC simulation to examine the local interaction between the reconnection guide field and thermodynamic variables during reconnection onset in a region of initially depleted thermal energy and enhanced magnetic energy in a large guide field background. We identify critical stages of the equilibration process, characterize intervals based on whether the pressure evolution is driven by changes in density or temperature, and discuss what these intervals imply about the evolution of local heat and work density. Finally, we examine power densities associated with electromagnetic field time evolution and electromagnetic energy transfer and compare to those related to thermodynamic changes.

physics.plasm-ph↗