Shocks and instabilities in the partially ionised solar atmosphere

Hillier, Andrew; Snow, Ben

doi:10.1016/j.asr.2022.08.079

Cited by 5 publications

(3 citation statements)

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“…Consequently, this decoupling leads to intensified wave energy dissipation at the shocks compared with purely linear collisional damping. Readers interested in the properties of shocks in partially ionized plasma are directed to the review in [2].…”

Section: (A) Chromospheric Heatingmentioning

confidence: 99%

“…Waves are closely connected with instabilities and shocks, but neither instabilities nor shocks are the subject of this paper. Recent reviews on instabilities in partially ionized plasmas are [1,2]. Additionally, discussions on shocks can be found in [2].…”

Section: Introductionmentioning

confidence: 99%

“…Recent reviews on instabilities in partially ionized plasmas are [1,2]. Additionally, discussions on shocks can be found in [2]. Beyond the context of MHD waves, the role of partial ionization effects in the solar plasma has been discussed in [3,4], while the similarities between the ion-neutral interaction in the chromosphere and in the ionosphere of the Earth have been explored in [5].…”

Section: Introductionmentioning

confidence: 99%

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Magnetohydrodynamic waves in the partially ionized solar plasma

Soler

2024

Phil. Trans. R. Soc. A.

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This paper provides a comprehensive review of recent theoretical investigations concerning magnetohydrodynamic (MHD) waves in partially ionized solar plasma. First, we examine the properties of linear MHD waves in a uniform partially ionized plasma and discuss the relevant effects arising from partial ionization. Subsequently, we delve into MHD wave studies in the more intricate settings of the lower solar atmosphere and solar prominences. These investigations involve topics such as MHD waves in magnetic flux tubes, wave excitation, linear and nonlinear mode coupling and wave heating. We outline new challenges that future research should tackle. This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.

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Section: (A) Chromospheric Heatingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetohydrodynamic waves in the partially ionized solar plasma

Soler

2024

Phil. Trans. R. Soc. A.

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The Fibre Resolved OpticAl and Near-Ultraviolet Czerny–Turner Imaging Spectropolarimeter (francis)

Jess,

Grant,

Bate

et al. 2023

Sol Phys

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The solar physics community is entering a golden era that is ripe with next-generation ground- and space-based facilities, advanced spectral inversion techniques, and realistic simulations that are becoming more computationally streamlined and efficient. With ever-increasing resolving power stemming from the newest observational telescopes, it becomes more challenging to obtain (near-)simultaneous measurements at high spatial, temporal and spectral resolutions, while operating at the diffraction limit of these new facilities. Hence, in recent years there has been increased interest in the capabilities integral field units (IFUs) offer towards obtaining the trifecta of high spatial, temporal and spectral resolutions contemporaneously. To date, IFUs developed for solar physics research have focused on mid-optical and infrared measurements. Here, we present an IFU prototype that has been designed for operation within the near-ultraviolet to mid-optical wavelength range, which enables key spectral lines (e.g., Ca ii H/K, H$\beta $ β , Sr ii, Na i D1/D2, etc.) to be studied, hence providing additional spectral coverage to the instrument suites developed to date. The IFU was constructed as a low-budget proof-of-concept for the upcoming $2\text{ m}$ 2 m class Indian National Large Solar Telescope and employs circular cross-section fibres to guide light into a Czerny–Turner configuration spectrograph, with the resulting spectra captured using a high quantum efficiency scientific CMOS camera. Mapping of each input fibre allows for the reconstruction of two-dimensional spectral images, with frame rates exceeding $20\text{ s}^{-1}$ 20 s − 1 possible while operating in a non-polarimetric configuration. Initial commissioning of the instrument was performed at the Dunn Solar Telescope, USA, during August 2022. The science verification data presented here highlights the suitability of fibre-fed IFUs operating at near-ultraviolet wavelengths for solar physics research. Importantly, the successful demonstration of this type of instrument paves the way for further technological developments to make a future variant suitable for upcoming ground-based and space-borne telescope facilities.

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Two fluid dynamics in solar prominences

González Manrique,

Khomenko,

Collados

et al. 2024

A&A

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Solar prominences contain a significant number of neutral species. The dynamics of the ionised and neutral fluids composing the prominence plasma can be slightly different if the collisional coupling is not strong enough. The differential dynamics can be discerned by tracing line-of-sight velocities using observational techniques. Large-scale velocities can be quantified by measuring the global local and instantaneous displacement of spectral lines by the Doppler effect. Small-scale velocities leave their imprint on the width of spectral lines. In addition, these small-scale velocities can have a thermal (pure stochastic motion) nature or a non-thermal (small-scale unresolved instabilities, high-frequency waves, etc.) origin. For this work, we used one spectral line of ionised and two spectral lines of neutral elements to measure the resolved and unresolved velocities in a prominence with the aim to investigate the possible decoupling of the observed charged and neutral species. A faint prominence was observed with the German Vacuum Tower Telescope (VTT) on June 17, 2017. Time series consisting of repeated ten-position scans over the prominence were performed while simultaneously recording the intensity spectra of the 854.2 nm 656.28 nm, and 587.56 nm lines. The line-of-sight velocities and the Doppler width of the three spectral lines were determined at every spatial position and temporal moment. To make sure all spectral lines were sampling the same plasma volume, we applied selection criteria to identify locations with optically thin plasma. In addition, asymmetric or double-peaked profiles were also excluded for the analysis, since (even in an optically thin regime) they are indicative of the presence of strong velocity gradients or multiple components in the line of sight. Thus, only optically thin, symmetric, single-lobed profiles were retained for this study. As an additional reliability test of the selection criteria, we have also compared our results with optical thickness calculations. After the application of all the selection criteria, only a region close to the prominence border met all requirements. The velocities of the three spectral lines turned out to be very similar over this region, with the ionised showing velocity excursions systematically larger compared to those of the neutral lines of and at some moments. The latter was found to be much closer to each other. Most of the velocity differences were below 1 The analysis of the Doppler widths indicated that the line shows an excess of unresolved motions. We cannot establish whether these velocities are related to a different temperature of the ions or to unresolved small-scale motions due to any non-thermal mechanism. The dynamics of the ionised and neutral plasma components in the observed prominence were very close to one another. The differences found may indicate that a localised decoupling between ions and neutrals may appear at particular spatial locations or instants of time. Indications of different unresolved motions between those species have also been obtained.

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Shocks and instabilities in the partially ionised solar atmosphere

Cited by 5 publications

References 115 publications

Magnetohydrodynamic waves in the partially ionized solar plasma

Magnetohydrodynamic waves in the partially ionized solar plasma

The Fibre Resolved OpticAl and Near-Ultraviolet Czerny–Turner Imaging Spectropolarimeter (francis)

Two fluid dynamics in solar prominences

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