Solar Spicules

Beckers, J. M.

doi:10.1146/annurev.aa.10.090172.000445

Cited by 303 publications

(217 citation statements)

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“…Spicules seemed to be wider in the Ca II H line than in the H α line (Beckers 1972). Pasachoff et al (2009) estimated the mean diameter of spicules as 660 ± 200 km using high-resolution observations of SST in H α , which fits the old observational data.…”

Section: Main Properties Of Limb Spiculesmentioning

confidence: 63%

Numerical simulations of spicule formation in the solar atmosphere

Murawski¹,

Zaqarashvili

2010

A&A

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Context. We study the upward propagation of a localized velocity pulse that is initially launched below the transition region within the solar atmosphere. The pulse quickly steepens into a shock, which may lead to the formation of spicules. Aims. We aim to explore the spicule formation scenario in the framework of the rebound shock model. Methods. We solve two-dimensional time-dependent magnetohydrodynamic equations numerically to find spatial and temporal dynamics of spicules.Results. The numerical simulations show that the strong initial pulse may lead to the quasi periodic rising of chromospheric material into the lower corona in the form of spicules. The periodicity results from the nonlinear wake that is formed behind the pulse in the stratified atmosphere. The superposition of rising and falling off plasma portions resembles the time sequence of single and double (sometimes even triple) spicules, which is consistent with observational findings. Conclusions. The two-dimensional rebound shock model may explain the observed speed, width, and heights of type I spicules, as well as observed multi-structural and bi-directional flows. The model also predicts the appearance of spicules with 3-5 min period due to the consecutive shocks.

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Section: Main Properties Of Limb Spiculesmentioning

confidence: 63%

Numerical simulations of spicule formation in the solar atmosphere

Murawski¹,

Zaqarashvili

2010

A&A

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“…To visualize, connect, and interpret the data we made extensive use of CRISPEX (Vissers & Rouppe van der Voort 2012 Beckers 1968Beckers , 1972 Pereira et al (2013) showed that by just degrading the Hinode data to similar conditions of earlier observations, one can derive the properties of classical spicules. The authors also compared SOT BFI Ca II H filtergrams with NFI Hα wing filtergrams and concluded that the spicules were very similar in both lines.…”

Section: Observationsmentioning

confidence: 99%

“…From early observations (e.g., Roberts 1945;Lippincott 1957) the early life of spicules was observed as an apparent upward motion. This view has so far stood the test of time: most studies agree that spicules show an upward motion in the early phase of their lives (e.g., Beckers 1968Beckers , 1972Nishikawa 1988;Suematsu et al 1995;De Pontieu et al 2004;Tsiropoula et al 2012). What happens in the later stages was unclear early on (Beckers 1968), and from Hinode Ca II H filtergrams it appears that spicules can be divided into two distinct groups ): type I spicules show a rise and fall, while type II spicules seem more violent and simply fade from Ca II H filtergrams with no downward motion observed (type II spicules dominate in quiet Sun and coronal holes; see Pereira et al 2012).…”

Section: Appearance and Disappearancementioning

confidence: 99%

“…Their very existence and transient, fast motions have been a challenge to explain. Much work has been carried out on this subject, with early reviews by Beckers (1968Beckers ( , 1972 and later reviews by Sterling (2000), Rutten (2012), and Tsiropoula et al (2012). Some of the most pressing questions about spicules are (1) what drives them and (2) what is their contribution to the transfer of energy and mass from the photosphere to the corona.…”

Section: Introductionmentioning

confidence: 99%

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THE APPEARANCE OF SPICULES IN HIGH RESOLUTION OBSERVATIONS OF Ca ii H AND Hα

Pereira

Voort

Carlsson

2016

ApJ

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Solar spicules are chromospheric fibrils that appear everywhere on the Sun, yet their origin is not understood. Using high resolution observations of spicules obtained with the Swedish 1 m Solar Telescope, we aim to understand how spicules appear in filtergrams and Dopplergrams, how they compare in Ca II H and Hα filtergrams, and what can make them appear and disappear. We find that spicules display a rich and detailed spatial structure, and show a distribution of transverse velocities that, when aligned with the line of sight, can make them appear at different Hα wing positions. They become more abundant at positions closer to the line core, reflecting a distribution of Doppler shifts and widths. In Hα width maps they stand out as bright features both on disk and off limb, reflecting their large Doppler motions and possibly higher temperatures than in the typical Hα formation region. Spicule lifetimes measured from narrowband images at only a few positions will be an underestimate because Doppler shifts can make them disappear prematurely from such images; for such cases, width maps are a more robust tool. In Hα and Ca II H filtergrams, off-limb spicules essentially have the same properties, appearance, and evolution. We find that the sudden appearance of spicules can be explained by Doppler shifts from their transverse motions, and does not require other convoluted explanations.

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“…The propagation may occur either upwards along the open vertical field lines in the umbra into the corona, or downwards into the deep interior of the sun. Beckers (1976) claims to have discovered an appreciable flux of Alfven waves in the surface layers of a sunspot: as much as 20-50? of the missing flux may be carried by the waves, according to Beckers.…”

Section: Heterogeneities Due To Magnetic Effectsmentioning

confidence: 99%

[no title]

Mullan¹

1977

Highlights astron.

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Heterogeneities in the solar atmosphere exist on many different length scales ranging from values as large as the solar radius (~106 km) down to features which are identifiable only by interferometry (~102 km). Rather than simply cataloguing the observed parameters of each and every known type of heterogeneity, I would like to concentrate on a few types of heterogeneities, with a view to identifying the information which is currently available concerning the physical mechanisms responsible for creating the in homogeneities. It is only if we can first identify the physics of each type of heterogeneity that we can hope to take even the first step towards predicting how each particular heterogeneity should scale to other stars. Since the present session is a joint discussion among mainly stellar astronomers, I feel that this approach is probably the most favorable method to present some of the large amount of information now available on solar features. Of course we expect that our solar information will be of most use to stellar astronomers in interpreting observations of stars which have similar spectral types to the sun. Nevertheless, we hope that nature will be kind enough to allow us to scale at least some of our information over a non-negligible area in the H.R. diagram.

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Solar Spicules

Cited by 303 publications

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Numerical simulations of spicule formation in the solar atmosphere

Numerical simulations of spicule formation in the solar atmosphere

THE APPEARANCE OF SPICULES IN HIGH RESOLUTION OBSERVATIONS OF Ca ii H AND Hα

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