Viscous Heating and Instabilities in the Partially Ionized Solar Atmosphere

Abstract

In weak magnetic fields ($\lesssim 50 \,\mbox{G}$), parallel and perpendicular viscosities, mainly from neutrals, may exceed magnetic diffusivities (Ohm, Hall, ambipolar) in the middle and upper chromosphere. Ion-driven gyroviscosity may dominate in the upper chromosphere and transition region. In strong fields ($\gtrsim 100\, \mbox{G}$), viscosities primarily exceed diffusivities in the upper chromosphere and transition region. Parallel and perpendicular viscosities, being similar in magnitude, dampen waves and potentially compete with ambipolar diffusion in plasma heating, potentially inhibiting Hall and ambipolar instabilities when equal. The perpendicular viscosity tensor has two components, ${\nu }_1$ and ${\nu }_2$, which differ slightly and show weak dependence on ion magnetization. Their differences, combined with shear, may destabilize waves, though magnetic diffusion introduces a cutoff for this instability. In configurations with a magnetic field $\mathbf{B}$ having vertical ($b_z=B_z/|\mathbf{B}|$) and azimuthal ($b_y=B_y/|\mathbf{B}|$) components, and a wavevector $\mathbf{k}$ with radial ($\kx=k_x/|\bf{k}|$) and vertical ($\kz=k_z/|\bf{k}|$) components, parallel viscosity and Hall diffusion can generate the viscous-Hall instability. Gyroviscosity further destabilizes waves in the upper regions. These findings indicate that the solar atmosphere may experience various viscous instabilities, revealing complex interactions between viscosity, magnetic fields, and plasma dynamics across different atmospheric regions.

20 pages, 17 figures, MNRAS (accepted)

References in corpus (18)

• Convectively driven vortex flows in the Sun
• Hall magnetohydrodynamics of partially ionized plasmas
• Small-scale solar magnetic fields
• Evidence of photospheric vortex flows at supergranular junctions observed by FG/SOT (Hinode)
• Two-dimensional Radiative Magnetohydrodynamic Simulations of Partial Ionization in the Chromosphere. II. Dynamics and Energetics of the Low Solar Atmosphere
• Simulations Show that Vortex Flows could Heat the Chromosphere in Solar Plage
• Vortex Flow Properties in Simulations of Solar Plage Region: Evidence for their role in chromospheric heating
• The Alfvénic nature of chromospheric swirls
• On the effects of ion-neutral interactions in solar plasmas
• Chromospheric Heating by MHD Waves and Instabilities
• Multi-fluid Approach to High-frequency Waves in Plasmas. II. Small-amplitude Regime in Partially Ionized Media
• Magnetic Tornado Properties: A Substantial Contribution to the Solar Coronal Heating via Efficient Energy Transfer
• A persistent quiet-Sun small-scale tornado III. Waves
• Coalescence Instability in Chromospheric Partially Ionised Plasmas
• Swirls in the Solar Corona
• Chromospheric Heating from Local Magnetic Growth and Ambipolar Diffusion Under Non-Equilibrium Conditions
• Influence of ambipolar and Hall effects on vorticity in 3D simulations of magneto-convection
• The non-ideal finite Larmor radius effect in the solar atmosphere