How Rotating Solar Atmospheric Jets Become Kelvin–Helmholtz Unstable

Zhelyazkov, I.; Chandra, Ramesh; Joshi, Reetika

doi:10.3389/fspas.2019.00033

Cited by 2 publications

(1 citation statement)

References 83 publications

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“…This instability may develop following the shear between the jet and its surroundings. For details about this sort of process in jets and coronal mass ejections (CMEs), see the review by Zhelyazkov et al (2019). (d) The main brightening at the top of the two vaults appears systematically to change position in the observations.…”

Section: Identification Of Observed Structural Elementsmentioning

confidence: 99%

Case study of multi-temperature coronal jets for emerging flux MHD models

Joshi

Chandra

Schmieder

et al. 2020

A&A

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Context. Hot coronal jets are a basic observed feature of the solar atmosphere whose physical origin is still actively debated. Aims. We study six recurrent jets that occurred in active region NOAA 12644 on April 4, 2017. They are observed in all the hot filters of AIA as well as cool surges in IRIS slit–jaw high spatial and temporal resolution images. Methods. The AIA filters allow us to study the temperature and the emission measure of the jets using the filter ratio method. We studied the pre-jet phases by analysing the intensity oscillations at the base of the jets with the wavelet technique. Results. A fine co-alignment of the AIA and IRIS data shows that the jets are initiated at the top of a canopy-like double-chambered structure with cool emission on one and hot emission on the other side. The hot jets are collimated in the hot temperature filters, have high velocities (around 250 km s−1) and are accompanied by cool surges and ejected kernels that both move at about 45 km s−1. In the pre-phase of the jets, we find quasi-periodic intensity oscillations at their base that are in phase with small ejections; they have a period of between 2 and 6 min, and are reminiscent of acoustic or magnetohydrodynamic waves. Conclusions. This series of jets and surges provides a good case study for testing the 2D and 3D magnetohydrodynamic emerging flux models. The double-chambered structure that is found in the observations corresponds to the regions with cold and hot loops that are in the models below the current sheet that contains the reconnection site. The cool surge with kernels is comparable with the cool ejection and plasmoids that naturally appears in the models.

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Section: Identification Of Observed Structural Elementsmentioning

confidence: 99%

Case study of multi-temperature coronal jets for emerging flux MHD models

Joshi

Chandra

Schmieder

et al. 2020

A&A

Self Cite

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Evolution of Kelvin–Helmholtz Instability in the Fan-spine Topology

Mishra

Singh

Srivastava

et al. 2021

ApJ

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We use multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory to study the evolution of the Kelvin–Helmholtz (K–H) instability in a fan-spine magnetic field configuration. This magnetic topology exists near an active region AR12297 and is rooted in a nearby sunspot. In this magnetic configuration, two layers of cool plasma flow in parallel and interact with each other inside an elongated spine. The slower plasma flow (5 km s−1) is the reflected stream along the spine’s field lines from the top, which interacts with the impulsive plasma upflows (114–144 km s−1) from below. This process generates a shear motion and subsequent evolution of the K–H instability. The amplitude and characteristic wavelength of the K–H unstable vortices increase, satisfying the criterion of the fastest-growing mode of this instability. We also describe how the velocity difference between two layers and the velocity of K–H unstable vortices are greater than the Alfvén speed in the second denser layer, which also satisfies the criterion of the growth of the K–H instability. In the presence of the magnetic field and sheared counterstreaming plasma as observed in the fan-spine topology, we estimate the parametric constant Λ ≥ 1, which confirms the dominance of velocity shear and the evolution of the linear phase of the K–H instability. This observation indicates that in the presence of complex magnetic field structuring and flows, the fan-spine configuration may evolve into rapid heating, while the connectivity changes due to the fragmentation via the K–H instability.

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How Rotating Solar Atmospheric Jets Become Kelvin–Helmholtz Unstable

Cited by 2 publications

References 83 publications

Case study of multi-temperature coronal jets for emerging flux MHD models

Case study of multi-temperature coronal jets for emerging flux MHD models

Evolution of Kelvin–Helmholtz Instability in the Fan-spine Topology

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