Penumbral Microjets in Sunspot Chromospheres: Evidence of Magnetic Reconnection

Katsukawa, Y.

doi:10.1007/978-981-10-7742-5_18

Cited by 2 publications

(2 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Movies associated to Appendix B are available at https://www.aanda.org A large automated sampling of PMJs (Drews & Rouppe van der Voort 2017) using highly spatially, temporally, and spectrally resolved Ca ii 8542 Å observations from the Swedish 1-m Solar Telescope (SST) at La Palma gives average PMJ lengths, widths, and lifetimes of 640 km, 210 km, and 90 s (with an 8 minute cut-off), respectively, on the same order of magnitude as previous values. PMJs are thought to be chromospheric in origin (Katsukawa et al 2007;), but they have been shown to have transition region (TR) responses (Vissers et al 2015;Tiwari et al 2016;Katsukawa et al 2018) and are visible in the Mg ii k, C ii, and Si iv slit-jaw images observed by the Interface Region Imaging Spectrograph satellite (IRIS, De Pontieu et al 2014). These observations suggest heating to TR temperatures as the studied PMJs show emission in the C ii and Si iv lines towards their tops.…”

Section: Introductionmentioning

confidence: 99%

A multi-diagnostic spectral analysis of penumbral microjets

Drews

Voort

2020

A&A

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

A multi-diagnostic spectral analysis of penumbral microjets

Drews

Voort

2020

A&A

View full text Add to dashboard Cite

show abstract

“…A large automated sampling of PMJs (Drews & Rouppe van der Voort 2017) using highly spatially, temporally, and spectrally resolved Ca ii 8542 Å observations from the Swedish 1-m Solar Telescope (SST) at La Palma gives average PMJ lengths, widths, and lifetimes of 640 km, 210 km, and 90 s (with an 8 minute cut-off), respectively, on the same order of magnitude as previous values. PMJs are thought to be chromospheric in origin (Katsukawa et al 2007;), but they have been shown to have transition region (TR) responses (Vissers et al 2015;Tiwari et al 2016;Katsukawa 2018) and are visible in the Mg ii k, C ii, and Si iv slit-jaw images observed by the Interface Region Imaging Spectrograph satellite (IRIS, De Pontieu et al 2014). These observations suggest heating to TR temperatures as the studied PMJs show emission in the C ii and Si iv lines towards their tops.…”

Section: Introductionmentioning

confidence: 99%

A multi-diagnostic spectral analysis of penumbral microjets

Drews,

van der Voort

2020

Preprint

View full text Add to dashboard Cite

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 Hα 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 Hα 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.

show abstract

Penumbral Microjets in Sunspot Chromospheres: Evidence of Magnetic Reconnection

Cited by 2 publications

References 17 publications

A multi-diagnostic spectral analysis of penumbral microjets

A multi-diagnostic spectral analysis of penumbral microjets

A multi-diagnostic spectral analysis of penumbral microjets

Contact Info

Product

Resources

About