Solar chromospheric spicules from the leakage of photospheric oscillations and flows

Pontieu, Bart De; Erdélyi, R.; James, S. P.

doi:10.1038/nature02749

Cited by 411 publications

(435 citation statements)

References 26 publications

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“…4c. This result supports the conclusion by De Pontieu et al (2004) that the p-mode energy may leak to the chromosphere via the inclined field line, and thus stimulate 5 min activities in the chromosphere. Another obvious peak of PSD profile is located at the period around 20 min, which seems to be caused by recurrent intensity enhancements associated with chromospheric jets.…”

Section: Chromospheric Activities In the Source Regionsupporting

confidence: 81%

“…The periodicity of the chromospheric spicules (∼5 min) in an AR plage was demonstrated to be produced by an energy leakage of the p-mode from the photosphere along inclined field lines (De Pontieu et al 2004). Intensity oscillations with periodicity longer than 10 min were found in polar plumes (Deforest & Gurman 1998;Banerjee et al 2000) and coronal bright points (Tian et al 2008b).…”

Section: Introductionmentioning

confidence: 98%

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Intermittent outflows at the edge of an active region – a possible source of the solar wind?

He¹,

Marsch²,

Tu³

et al. 2010

A&A

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Context. It has already been established that the solar wind may originate at the edges of active regions (ARs), but the key questions of how frequently these outflows occur, and at which height the nascent solar wind originates have not yet been addressed. Aims. We study the occurrence rate of these intermittent outflows, the related plasma activities beneath in the low solar atmosphere, and the interplanetary counterparts of the nascent solar wind outflow. Methods. We use the observations from XRT/Hinode and TRACE to study the outflow patterns. The occurrence frequency of the intermittent outflow is estimated by counting the occurrences of propagating intensity enhancements in height-time diagrams. We adopt observations of SOT/Hinode and EIS/Hinode to investigate the phenomena in the chromosphere associated with the coronal outflows. The ACE plasma and field in-situ measurements near Earth are used to study the interplanetary manifestations. Results. We find that in one elongated coronal emission structure, referred to as strand, the plasma flows outward intermittently, about every 20 min. The flow speed sometimes exceeds 200 km s −1 , which is indicative of rapid acceleration, and thus exceeds the coronal sound speed at low altitudes. The inferred flow speed of the soft-X-ray-emitting plasma component seems a little higher than that of the Fe ix/x-emitting plasma component. Chromospheric jets are found to occur at the root of the strand. Upflows in the chromosphere are also confirmed by blue-shifts of the He ii line. The heliospheric plasma counterpart close to the Earth is found to be an intermediate-speed solar wind stream. The AR edge may also deliver some plasmas to a fraction of the fast solar wind stream, most of which emanate from the neighboring CH. Conclusions. The possible origin of the nascent solar wind in the chromosphere, the observed excessive outflow speed of over 200 km s −1 in the lower corona, and the corresponding intermediate-speed solar wind stream in interplanetary space are all linked in our case study. These phenomena from the low solar atmosphere to the heliosphere near Earth in combination shed new light on the solar wind formation process. These observational results will constrain future modeling of the solar winds originating close to an AR.

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Section: Chromospheric Activities In the Source Regionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 98%

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

He¹,

Marsch²,

Tu³

et al. 2010

A&A

View full text Add to dashboard Cite

show abstract

“…De Pontieu et al (2004) propose that, as a result of fall off of acoustic cut-off frequency, p-modes may be channeled into the solar corona along inclined magnetic field lines. The oscillations then may be steepened into shocks producing spicules.…”

Section: Introductionmentioning

confidence: 99%

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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“…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%

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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Solar chromospheric spicules from the leakage of photospheric oscillations and flows

Cited by 411 publications

References 26 publications

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

Intermittent outflows at the edge of an active region – a possible source of the solar wind?

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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