PREDNASAJUCI / LECTURER :

Sergo Lomineishvili

(1) Astronomical Institute, Slovak Academy of Sciences,
059 60 Tatranská Lomnica

NAZOV / TITLE :

Kink instability of partially ionized and non-aligned plasma jets in the solar atmosphere

ABSTRAKT / ABSTRACT :

This study investigates the stability of chromospheric jets by analyzing the kink mode of
the Kelvin–Helmholtz instability (KHI) in partially ionized plasma. We examine how ambipolar
diffusion - represented via the Cowling conductivity within a single-fluid magnetohydrodynamic
(MHD) framework and non-alignment between the jet and the magnetic field, affects the
instability threshold and growth rates. Using a magnetic slab model and linear perturbation
theory for incompressible flows, we derive a general dispersion relation for non-aligned jets,
applying the appropriate continuity conditions for momentum and pressure. The analysis shows
how ambipolar diffusion and non-alignment largely modify the stability conditions:
chromospheric jets can become KH-unstable at flow velocities below the classical ideal MHD
threshold. We compute KHI growth times for different ionization degrees and flow
configurations, offering a comprehensive view of the parameter space that governs stability
and instability. Although the kink instability and KHI are closely related here—and both terms
are used throughout—their distinguishing features is discussed. The results emphasize the
critical role of partial ionization - associated with ambipolar diffusion, in controlling the
dynamics and stability of solar atmospheric jets and dominant effect of non-alignment is also
seen.