Penumbral microjets at high spatial and temporal resolution

Voort, L. H. M. Rouppe van der; Drews, Ainar

doi:10.1051/0004-6361/201935343

Cited by 8 publications

(1 citation statement)

References 32 publications

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“…These so-called penumbral microjets are typically short in length and the associated enhancement of emission in Ca II lines is short-lived (1-2 min - [75,76]). However, evidence seems to suggest there is little mass-motion associated with these features and they are potentially heating fronts associated with reconnection occurring lower in the atmosphere [77][78][79]. At present, it is unclear whether there is a connection between the occurrence of these microjets and the transverse waves-although the current dataset may enable such a comparison to take place.…”

Section: (C) Reconnection Drivenmentioning

confidence: 88%

Transverse motions in sunspot super-penumbral fibrils

Morton

Mooroogen

Henriques

2020

Phil. Trans. R. Soc. A.

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Sunspots have played a key role in aiding our understanding of magnetohydrodynamic (MHD) wave phenomena in the Sun’s atmosphere, and it is well known they demonstrate a number of wave phenomena associated with slow MHD modes. Recent studies have shown that transverse wave modes are present throughout the majority of the chromosphere. Using high-resolution Ca II 8542 Å observations from the Swedish Solar Telescope, we provide the first demonstration that the chromospheric super-penumbral fibrils, which span out from the sunspot, also show ubiquitous transverse motions. We interpret these motions as transverse waves, in particular the MHD kink mode. We compile the statistical properties of over 2000 transverse motions to find distributions for periods and amplitudes, finding they are broadly consistent with previous observations of chromospheric transverse waves in quiet Sun fibrils. The very presence of the waves in super-penumbral fibrils raises important questions about how they are generated, and could have implications for our understanding of how MHD wave energy is transferred through the atmosphere of a sunspot. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

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Section: (C) Reconnection Drivenmentioning

confidence: 88%

Transverse motions in sunspot super-penumbral fibrils

Morton

Mooroogen

Henriques

2020

Phil. Trans. R. Soc. A.

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A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

et al. 2021

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The Interface Region Imaging Spectrograph (IRIS) has been obtaining near- and far-ultraviolet images and spectra of the solar atmosphere since July 2013. IRIS is the highest resolution observatory to provide seamless coverage of spectra and images from the photosphere into the low corona. The unique combination of near- and far-ultraviolet spectra and images at sub-arcsecond resolution and high cadence allows the tracing of mass and energy through the critical interface between the surface and the corona or solar wind. IRIS has enabled research into the fundamental physical processes thought to play a role in the low solar atmosphere such as ion–neutral interactions, magnetic reconnection, the generation, propagation, and dissipation of waves, the acceleration of non-thermal particles, and various small-scale instabilities. IRIS has provided insights into a wide range of phenomena including the discovery of non-thermal particles in coronal nano-flares, the formation and impact of spicules and other jets, resonant absorption and dissipation of Alfvénic waves, energy release and jet-like dynamics associated with braiding of magnetic-field lines, the role of turbulence and the tearing-mode instability in reconnection, the contribution of waves, turbulence, and non-thermal particles in the energy deposition during flares and smaller-scale events such as UV bursts, and the role of flux ropes and various other mechanisms in triggering and driving CMEs. IRIS observations have also been used to elucidate the physical mechanisms driving the solar irradiance that impacts Earth’s upper atmosphere, and the connections between solar and stellar physics. Advances in numerical modeling, inversion codes, and machine-learning techniques have played a key role. With the advent of exciting new instrumentation both on the ground, e.g. the Daniel K. Inouye Solar Telescope (DKIST) and the Atacama Large Millimeter/submillimeter Array (ALMA), and space-based, e.g. the Parker Solar Probe and the Solar Orbiter, we aim to review new insights based on IRIS observations or related modeling, and highlight some of the outstanding challenges.

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A multi-diagnostic spectral analysis of penumbral microjets

Drews

Voort

2020

A&A

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Context. Penumbral microjets (PMJs) are short-lived, jet-like objects found in the penumbra of sunspots. They were first discovered in chromospheric lines and have later also been shown to exhibit signals in transition region (TR) lines. Their origin and manner of evolution is not yet settled. Aims. We perform a comprehensive analysis of PMJs through the use of spectral diagnostics that span from photospheric to TR temperatures to constrain PMJ properties. Methods We employed high-spatial-resolution Swedish 1-m Solar Telescope observations in the Ca II 8542 Å and H α lines, IRIS slit-jaw images, and IRIS spectral observations in the Mg II h & k lines, the Mg II 2798.75 Å & 2798.82 Å triplet blend, the C II 1334 Å & 1335 Å lines, and the Si IV 1394 Å & 1403 Å lines. We derived a wide range of spectral diagnostics from these and investigated other secondary phenomena associated with PMJs. Results. We find that PMJs exhibit varying degrees of signal in all of our studied spectral lines. We find low or negligible Doppler velocities and velocity gradients throughout our diagnostics and all layers of the solar atmosphere associated with these. Dark features in the inner wings of H α and Ca II 8542 Å imply that PMJs form along pre-existing fibril structures. We find evidence for upper photospheric heating in a subset of PMJs through emission in the wings of the Mg II triplet lines. There is little evidence for ubiquitous twisting motion in PMJs. There is no marked difference in onset-times for PMJ brightenings in different spectral lines. Conclusions. PMJs most likely exhibit only very modest mass-motions, contrary to earlier suggestions. We posit that PMJs form at upper photospheric or chromospheric heights at pre-existing fibril structures.

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Penumbral microjets at high spatial and temporal resolution

Cited by 8 publications

References 32 publications

Transverse motions in sunspot super-penumbral fibrils

Transverse motions in sunspot super-penumbral fibrils

A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

A multi-diagnostic spectral analysis of penumbral microjets

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