PREDNASAJUCI / LECTURER :

Elene Midelashvili

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

NAZOV / TITLE :

Kinematic Fragmentation and Resolution-dependent Fading of Type II Spicules

ABSTRAKT / ABSTRACT :

Type II spicules are highly dynamic, short-lived plasma jets that play an
important role in the dynamics of the solar chromosphere and the transport
of mass and energy toward the upper solar atmosphere. One of their most
intriguing observational properties is their rapid disappearance from
chromospheric spectral lines, commonly attributed to plasma heating to
transition-region temperatures. However, the contribution of plasma
instabilities and small-scale structuring to this apparent fading remains
insufficiently understood.

In this seminar, I will present results from high-resolution 2.5D
magnetohydrodynamic (MHD) simulations investigating the nonlinear evolution
of spicule-like jets driven by transverse oscillations. We demonstrate that
kink-like motions trigger the Kelvin–Helmholtz instability, leading to
fragmentation of initially coherent jets into fine-scale plasma strands.
Synthetic emission diagnostics reveal that this fragmentation, combined
with limited instrumental spatial resolution, can produce apparent fading
without significant plasma heating. Furthermore, the results show a delay
between the physical onset of instability and observational fading,
accompanied by a transition from coherent oscillations to unresolved
velocity fluctuations. These findings provide an alternative mechanism
contributing to spicule disappearance and offer testable predictions for
high-resolution solar observations.