Dynamic kink instability and transverse motions of solar spicules
arXiv:2004.04401 · doi:10.3847/2041-8213/ab881d
Abstract
Hydrodynamic jets are unstable to the kink instability (m=1 mode in cylindrical geometry) owing to the centripetal force, which increases the transverse displacement of the jet. When the jet moves along a magnetic field, then the Lorentz force tries to decrease the displacement and stabilises the instability of sub-Alfvenic flows. The threshold of the instability depends on the Alfven Mach number (the ratio of Alfven and jet speeds). We suggest that the dynamic kink instability may be of importance to explain observed transverse motions of type II spicules in the solar atmosphere. We show that the instability may start for spicules which rise up at the peripheries of vertically expanding magnetic flux tubes owing to the decrease of the Alfven speed in both, the vertical and the radial directions. Therefore, inclined spicules may be more unstable and have more higher transverse speeds. Periods and growth times of unstable modes in the conditions of type II spicules have the values of 30 s and 25-100 s, respectively, which are comparable to the life time of the structures. This may indicate to the interconnection between high speed flow and rapid disappearance of type II spicules in chromospheric spectral lines.
arXiv comment5 pages, 4 figures, accepted in ApJL
References in corpus (19)
- A Tale Of Two Spicules: The Impact of Spicules on the Magnetic Chromosphere
- Ubiquitous torsional motions in type II spicules
- On the generation of solar spicules and Alfvénic waves
- On-disk counterparts of type II spicules in the Ca II 854.2 nm and Halpha lines
- Oscillations and waves in solar spicules
- Propagating waves along spicules
- Solar fine-scale structures. I. Spicules and other small-scale, jet-like events at the chromospheric level: observations and physical parameters
- An Interface Region Imaging Spectrograph first view on Solar Spicules
- Alfvén Wave Dissipation in the Solar Chromosphere
- Observation of kink waves in solar spicules
- Statistical properties of the Disk Counterparts of Type II Spicules from simultaneous observations of RBEs in Ca II 8542 and Hα
- Doppler shift oscillations in solar spicules
- Transverse oscillations in chromospheric mottles
- Heating signatures in the disk counterparts of solar spicules in IRIS observations
- The Dynamics of Rapid Redshifted and Blueshifted Excursions in the Solar Halpha line
- Transverse Wave Induced Kelvin-Helmholtz Rolls in Spicules
- Kelvin-Helmholtz instability in solar chromospheric jets: theory and observation
- Kelvin-Helmholtz instability of twisted magnetic flux tubes in the solar wind
- Bridging the Gap: Capturing the Ly Counterpart of a Type-II Spicule and its Heating Evolution with VAULT2.0 and IRIS Observations