A time evolution study of limb spicule spectra

Krall, K. R.; Bessey, R. J.; Beckers, J. M.

doi:10.1007/bf00157556

Cited by 10 publications

(7 citation statements)

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“…Alissandrakis (1973) derived electron densities between 6 × 10 10 cm −3 and 1.2 × 10 11 cm −3 , and temperatures between 10,000 and 15,000 K at altitude of 5.4 Mm. Later, Krall et al (1976) found electron densities between 1.1 × 10 11 cm −3 at 6 Mm and 2 × 10 10 cm −3 at 10 Mm, with temperature ranging from 12,000 to 15,000 K. These authors also determined the micro-turbulent velocities with values between 12 and 22 km s −1 . In contrast to Beckers (1972), Matsuno, & Hirayama (1988) found more complex temperature variations with the altitude, giving temperature of 9,000 K at 2.2 Mm, 5,000 K at 3.2 Mm and 8,200 K at 6 Mm.…”

Section: Introductionmentioning

confidence: 92%

IRIS Mg ii Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole

Tei

Gunár

Heinzel

et al. 2020

ApJ

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We investigated the off-limb spicules observed in the Mg II h and k lines by IRIS in a solar polar coronal hole. We analyzed the large dataset of obtained spectra to extract quantitative information about the line intensities, shifts, and widths. The observed Mg II line profiles are broad and doublepeaked at lower altitudes, broad but flat-topped at middle altitudes, and narrow and single-peaked with the largest Doppler shifts at higher altitudes. We use 1D non-LTE vertical slab models (i.e. models which consider departures from Local Thermodynamic Equilibrium) in single-slab and multislab configurations to interpret the observations and to investigate how a superposition of spicules along the line of sight (LOS) affects the synthetic Mg II line profiles. The used multi-slab models are either static, i.e. without any LOS velocities, or assume randomly assigned LOS velocities of individual slabs, representing the spicule dynamics. We conducted such single-slab and multi-slab modeling for a broad set of model input parameters and showed the dependence of the Mg II line profiles on these parameters. We demonstrated that the observed line widths of the h and k line profiles are strongly affected by the presence of multiple spicules along the LOS. We later showed that the profiles obtained at higher altitudes can be reproduced by single-slab models representing individual spicules. We found that the multi-slab model with a random distribution of the LOS velocities ranging from -25 to 25 km s −1 can well reproduce the width and the shape of Mg II profiles observed at middle altitudes.

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Section: Introductionmentioning

confidence: 92%

IRIS Mg ii Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole

Tei

Gunár

Heinzel

et al. 2020

ApJ

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“…However, despite being reported some temperature variations, based on analyses of the T e − n e curves at different heights, the pioneering work of Beckers (1968) concluded that the spicule intensities in chromospheric lines do not yield information about temperature variation and hence observed spectral characteristics in principle can be reproduced by a spicule model with uniform temperature (see page 408 therein). In this context Krall et al (1976) also mentioned that Hα emission is a rather sensitive indicator of electron density and relatively independent of temperature over a large temperature range (see page 100 therein). Our results confirms this as we fitted multiple Ca II profiles with constant temperature in four selected snapshots from the spicule lifetime.…”

Section: Discussionmentioning

confidence: 99%

“…Our analyses shows that the spicule plasma is isothermal having the uniform temperature of 9 560 K along its length in the time interval of 7 minutes. Early and also recent measurements reported temperature variation along the spicule axis (Beckers 1968(Beckers , 1972Alissandrakis 1973;Krall et al 1976;Matsuno & Hirayama 1988;Alissandrakis et al 2018). However, despite being reported some temperature variations, based on analyses of the T e − n e curves at different heights, the pioneering work of Beckers (1968) concluded that the spicule intensities in chromospheric lines do not yield information about temperature variation and hence observed spectral characteristics in principle can be reproduced by a spicule model with uniform temperature (see page 408 therein).…”

Section: Discussionmentioning

confidence: 99%

“…Over the main part of the spicule the τ is well above one, thus classifying the spicule plasma as optically thick in the Ca II line center. Krall et al (1976) performed theoretical calculations of the spicule optical thickness τ 8542 in the Ca II line center for the temperatures and electron densities ranging from 10 000 K to 20 000 K and from 2 × 10 10 cm −3 to 1 × 10 11 cm −3 , respectively, but inferring τ 8542 mostly of the order of 1 × 10 −2 − 1 × 10 −3 . They assumed the spicule thickness of 1 425 km (see page 100 therein), thus larger than the thickness of 1 000 km employed here (Table 1).…”

Section: Discussionmentioning

confidence: 99%

“…The temperature of the spicules reported by Beckers (1968) between the heights of 2 − 8 Mm is ∼ 9 000 − 16 000 K and the electron densities between 4 − 8 Mm are 1.5 × 10 11 − 4.3 × 10 10 cm −3 . Alissandrakis (1973) and Krall et al (1976) implemented the same method and obtained similar results for electron density and temperature as Beckers (1968). Socas-Navarro & Elmore (2005) used multiline full Stokes observations of spicules in the Ca II 8498, 8542 Å, and He I 10830 Å lines to derive spicule properties.…”

Section: Introductionmentioning

confidence: 99%

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Semi-empirical models of spicule from inversion of Ca II 8542 Å line

Kuridze,

Socas-Navarro,

Koza

et al. 2020

Preprint

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We study a solar spicule observed off-limb using high-resolution imaging spectroscopy in the Ca II 8542 Å line obtained with the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1-m Solar Telescope. Using a new version of the non-LTE code NICOLE specifically developed for this problem we invert the spicule single-and double-peak line profiles. This new version considers off-limb geometry and computes atomic populations by solving the 1D radiative transfer assuming a vertical stratification. The inversion proceeds by fitting the observed spectral profiles at 14 different heights with synthetic profiles computed in the model by solving the radiative transfer problem along its length. Motivated by the appearance of double-peak Ca II 8542 Å spicule profiles, which exhibit two distinct emission features well separated in wavelength, we adopt a double-component scenario. We start from the ansatz that the spicule parameters are practically constant along the spicule axis for each component, except for a density drop. Our results support this ansatz by attaining very good fits to the entire set of 14 × 4 profiles (14 heights and 4 times). We show that the double-component model with uniform temperature of 9 560 K, exponential decrease of density with a height scale of 1 000 − 2 000 km, and the counter-oriented line-of-sight velocities of components reproduce the double-peak line profiles at all spicule segments well. Analyses of the numerical response function reveals the necessity of the inversions of spectra at multiple height positions to obtain height-dependent, degeneracy-free reliable model with a limited number of free parameters.

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Non‐rigid rotation of solar spicules

Pishkalo¹

1994

Astron Nachr

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Ha profiles of chromospheric spicules computed for a variety of rotational behavior are compared with an observed profile, which was derived by averaging 11 H a profiles taken near times of maximum spicule intensity. If turbulent velocity is small or equals zero, calculated profiles are in good agreement with the observed one under the conditions that rotation is non-rigid (faster rotation further away from the axis of the spicule) and the source function decreases in the direction from the spicule axis to the periphery. The comparison of calculated and observed tilts of spicule spectra relative to the direction of dispersion seems to corraborate the non-rigid character of spicular rotation.Key words: Sun -chromosphere -spicules A A A subject classification: 073 IntroductionTilts of spicule spectra relative to the direction of dispersion as well as large widths of spicule emission lines point to the possible presence of rotation in spicules. Large observed widths of spicular profiles may be explained by several causes other than rotation: high temperatures, large optical depths of spicules and broadening of profiles because of the self-absorption, the high turbulence of the spicular plasma, the superposition of some spectral features with different Doppler shifts in the line of sight, or the radial compression or expansion of spicules while conserving axial symmetry. But any one of these factors alone can not completely satisfy all the observational d a t a (Livshitz 1966, Beckers 1968, Beckers 1972, Ivanchuk and Pishkalo 1989, Ivanchuk and Pishkalo 1992.Tilted spectral features have been explained most simply as due to the superposition of several neighbouring spicules with different Doppler shifts in the line of sight, because of still insufficient spatial resolution of the observations. However, tilts are also observed at large heights in the chromosphere, where the superposition is unlikely. Therefore, spectral tilts cannot be fully explained by superposition of several different spicules in the line of sight (Beckers 1966, Pasachoff et al. 1968.It seems rather probable that tilts are real phenomena because oftilts are observed at times of good seeing and because features with large Doppler shifts and spatially isolated narrow features also have tilts (Beckers 1966, Alissandrakis 1973, Krall et al. 1976, Pishkalo 1986).In Ha and K C a I1 lines, observed spectral tilts reach several degrees. Pishkalo (1986) estimated that 28%of Ha spicules had non-zero tilts and the averaged tilt of these spicules was 1'25'. Many spicules had spectral tilts in isolated moments of their lifetimes only. A tilt occured during brief time intervals for about 50% of all the spicules. There are also examples where t h e tilt was constant for a prolonged time interval (about 4 minutes) and where the tilt changed steadily and might even reverse its sign (Pasachoff et al. 1968, Pishkalo 1986.T h e calculations and the analysis of the rotation effects on broadening of spicule profiles made by Rodionov (1968), Avery (1970), Mamedov and...

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A time evolution study of limb spicule spectra

Cited by 10 publications

References 11 publications

IRIS Mg ii Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole

IRIS Mg ii Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole

Semi-empirical models of spicule from inversion of Ca II 8542 Å line

Non‐rigid rotation of solar spicules

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