From the near-Earth solar wind to the intracluster medium of galaxy clusters, collisionless, high-beta, magnetized plasmas pervade our universe. Energy and momentum transport from large-scale fields and flows to small scale motions of plasma particles is ubiquitous in these systems, but a full picture of the underlying physical mechanisms remains elusive. The transfer is often mediated by a turbulent cascade of Alfv{é}nic fluctuations as well as a variety of kinetic instabilities; these processes tend to be multi-scale and/or multi-dimensional, which makes them difficult to study using spacecraft missions and numerical simulations alone (Dorfman et al. 2023; Lichko et al. 2020, 2023). Meanwhile, existing laboratory devices struggle to produce the collisionless, high ion beta ($\beta_i \gtrsim 1$), magnetized plasmas across the range of scales necessary to address these problems. As envisioned in recent community planning documents (Carter et al. 2020; Milchberg and Scime 2020; Baalrud et al. 2020; Dorfman et al. 2023; National Academies of Sciences, Engineering, and Medicine 2024, it is therefore important to build a next generation laboratory facility to create a $\beta_i \gtrsim 1$, collisionless, magnetized plasma in the laboratory for the first time. A Working Group has been formed and is actively defining the necessary technical requirements to move the facility towards a construction-ready state. Recent progress includes the development of target parameters and diagnostic requirements as well as the identification of a need for source-target device geometry. As the working group is already leading to new synergies across the community, we anticipate a broad community of users funded by a variety of federal agencies (including NASA, DOE, and NSF) to make copious use of the future facility.
The radiation mechanism of decimetric wideband and pulsating radio bursts from the Sun (in terms of decimetric type-IV (t-IVdm) burst) and other flaring stars is a long-standing problem. Early investigations were based on the leading-spot hypothesis for the sun and yielded contradictory results. Here we provide essential evidence to support the scenario that these bursts are induced by the electron cyclotron maser emission (ECME) driven by energetic electrons mirrored in converging sunspot fields. This is done by analyzing 2 flare-associated t-IVdm bursts that are selected from a larger sample of 60 bursts recorded during 2010-2014, according to the levels of polarization and whether the source-field orientation can be unambiguously determined. We further modeled the transport of downward-streaming energetic electrons along a coronal loop and found most electrons get mirrored within the specific altitude range of 20-100 Mm. This explains why such bursts tend to have well-defined spectral ranges. The study greatly expands the application of ECME in solar radio astronomy and provides solar samples for similar bursts from other flaring stars.
The linear stability of global non-axisymmetric modes in differentially rotating, magnetized, non-ideal plasma is crucial for understanding turbulence and transport phenomena. We investigate the competition between the local Magneto-Rotational Instability (MRI) and the Magneto-Curvature Instability (MCI)--a distinct non-axisymmetric low-frequency curvature-driven global branch--by developing and applying a non-ideal global spectral method, validated against NIMROD code simulations, and an extended effective potential formalism. Our analysis reveals that the global, low-frequency MCI persists at low magnetic Reynolds numbers (Rm), whereas the localized, high-frequency MRI is stabilized by diffusive broadening of its structure around its Alfvénic resonances. Consequently, we identify the global MCI as the primary onset mechanism for magnetohydrodynamic instability in systems with finite curvature, e.g., astrophysical rotators. We establish distinct parameter regimes for mode dominance: MCI prevails in geometrically moderate-thickness disks with high curvature and intermediate radial gaps, while MRI dominates in thin, low-curvature disks with large radial gaps. Mode competition is also highly sensitive to the flow profile, particularly vorticity and its gradient, with non-uniform shear profiles exhibiting more robust instability due to flow-curvature and shear contributions. A key outcome is the development of "spectral diagrams" derived from the global spectral method. These diagrams comprehensively map dominant instabilities and their characteristics, offering a predictive tool for critical onset parameters (i.e., flow curvature, magnetic field, and Rm) and facilitating the interpretation of experimental and simulation results. Notably, these diagrams demonstrate that the global MCI is generally the sole unstable mode at the initial onset of instability.
Understanding cosmic ray (CR) diffusion in a partially ionized medium is both crucial and challenging. In this study, we investigate CR superdiffusion in turbulent, partially ionized media using high-resolution 3D two-fluid simulations that treat ions and neutrals separately. We examine the influence of neutral-ion decoupling and the associated damping of turbulence on CR propagation in both transonic and supersonic conditions. Our simulations demonstrate that neutral-ion decoupling significantly damps velocity, density, and magnetic field fluctuations at small scales, producing spectral slopes steeper than those of Kolmogorov and Burgers scaling. We also identify an intermediate coupling regime in which neutrals remain partially coupled with ions, leading to a steepening of kinetic energy spectra in both fluids. Shocks can enhance the neutral-ion coupling, thereby reducing the differences between neutral and ion density structures. Moreover, the damping of magnetic field fluctuations substantially decreases pitch angle scattering, which increases CR parallel mean free paths. As a result, CR perpendicular transport transitions between two distinct superdiffusive regimes: a scattering-dominated regime with perpendicular displacement proportional to $t^{3/4}$, and a scattering-free regime dominated by magnetic field line wandering, with perpendicular displacement scaling as $t^{3/2}$. When the pitch angle is large, the effects of magnetic mirroring, naturally arising in magnetohydrodynamic turbulence, become significant, enhancing the confinement (but not fully trapping) of CRs and inducing oscillations in their perpendicular displacement. These results highlight the necessity of incorporating two-fluid effects for accurately modeling CR transport in partially ionized environments such as molecular clouds and dense interstellar clumps.