Wavelet analysis of solar macro-spicule recurrences

Ajabshirizadeh, A.; Tavabi, E.; Koutchmy, S.

doi:10.1016/j.newast.2007.07.001

Cited by 15 publications

(5 citation statements)

References 17 publications

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“…Fig. 4 and 5 show a lot of doublet threads occurring in all heights and we know that the overlapping effect is not important for high levels (Ajabshirizadeh et al 2008).…”

Section: Discussionmentioning

confidence: 85%

“…In this figure we clearly see that transversal displacements at all heights exist. But we know that in the lower layers of the solar chromosphere the number of spicules is dramatically higher than in the upper layers (Lippincott 1957& Athay 1959, so the overlapping effect (Ajabshirizadeh et al 2008) is rapidly decreasing with the height. If the transverse motion was due to the overlapping effect it should have changed in different levels, which is not observed.…”

Section: -C Alfven Waves and Helical Motions Of Spiculesmentioning

confidence: 97%

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A statistical analysis of the SOT-Hinode observations of solar spicules and their wave-like behavior

2011

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Spicules are an important very dynamical and rather cool structure extending between the solar surface and the corona. They are partly filling the space inside the chromosphere and they are surrounded by a transition thin layer. New space observations taken with the SOT of the Hinode mission shed some light on their still mysterious formation and dynamics. Here we restrict the analysis to the most radial and the most interesting polar spicules situated at the base of the fast solar wind of coronal holes.We consider a first important parameter of spicules as observed above the solar visible limb: their apparent diameter as a function of the height above the limb which determines their aspect ratio and leads to the discussion of their magnetic origin using the flux tube approximation. We found that indeed spicules show a whole range of diameters, including unresolved "interacting spicules" (I-S), depending of the definition chosen to characterize this ubiquitous dynamical phenomenon occurring into a low coronal surrounding. Superposition effects along the line of sight have to be taken into account in order to correctly measure individual spicules and look at I-S. We take advantage of the so-called Madmax operator to reduce these effects and improve the visibility of these hair-like features. An excellent time sequence of images obtained above a polar region with the Hinode SOT through the HCaII filter with a cadence of 8 s was selected for analysis. 1-D Fourier amplitude spectra (AS) made at different heights above the limb are shown for the first time. A definite signature in the 0.18 to 0.25 Mm range exists, corresponding to the occurrence of the newly discovered

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“…Fig. 4 and 5 show a lot of doublet threads occurring in all heights and we know that the overlapping effect is not important for high levels (Ajabshirizadeh et al 2008).…”

Section: Discussionmentioning

confidence: 85%

Section: -C Alfven Waves and Helical Motions Of Spiculesmentioning

confidence: 97%

A statistical analysis of the SOT-Hinode observations of solar spicules and their wave-like behavior

2011

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“…This method can be understood as a convolution with the derivative of a 2D Gaussian function which enhances the visibility of thin structures, equivalent to a 2D Fourier filtering and it is very useful for evaluating W-L coronal eclipse images see November and Koutchmy, 1986. There exist a large number of numerical, automated codes, specialized either for the case of curvilinear features (Ajabshirizadeh et al 2008, Aschwanden et al2008and Biskri et al 2010), but there is not a general pattern tracing code which has a superior performance in all kinds of data and features, so for a particular data set and structure it needs to be customized to the particular morphological properties of a given data set, noting also that the manual tracing are not suitable when a large population of similar structures are analyzed.…”

Section: Proposed Algorithms To Evaluate Imagesmentioning

confidence: 99%

Increasing the Fine Structure Visibility of the Hinode SOT Ca ii H Filtergrams

2012

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and koutchmy@iap.fr). AbstractWe present the improved so-called Madmax (OMC) operator selecting maxima of convexities computed in multiple directions around each pixel rewritten in MatLab and shown to be very efficient for pattern recognition.The aim of the algorithm is to trace the bright hair-like features (for ex. chromospheric thin jets or spicules) of solar ultimate observations polluted by a noise of different origins. This popular spatial operator uses the second derivative in the optimally selected direction for which its absolute value has a maximum value. Accordingly, it uses the positivity of the resulting intensity signal affected by a superposed noise. The results are illustrated using a test artificially generated image and real SOT (Hinode) images are also used, to make your own choice of the sensitive parameters to use in improving the visibility of images.

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“…The existence of five-minute oscillations in spicules were originally reported by Nikolsky & Platova (1971), Kulidzanishvili & Nikolsky (1978), and others, including spectroscopically performed observations with a large aperture coronagraph. More recently, image sequences have been studied by De Pontieu et al (2004), Xia et al (2005), and Ajabshirizadeh et al (2008). Oscillations in spicules with even shorter periods have been reported by Nikolsky & Platova (1971).…”

Section: Introductionmentioning

confidence: 99%

Alfvénic waves in polar spicules

Tavabi

Koutchmy

Ajabshirizadeh

et al. 2014

A&A

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Context. For investigating spicules from the photosphere to coronal heights, the new Hinode/SOT long series of high-resolution observations from space taken in CaII H line emission offers an improved way to look at their remarkable dynamical behavior using images free of seeing effects. They should be put in the context of the huge amount of already accumulated material from groundbased instruments, including high-resolution spectra of off-limb spicules. Aims. Both the origin of the phenomenon and the significance of dynamical spicules for the heating above the top of the photosphere and the fuelling of the chromospheric and the transition region need more investigation, including of the possible role of the associated magnetic waves for the corona higher up. Methods. We analyze in great detail the proper transverse motions of mature and tall polar region spicules for different heights, assuming that there might be Helical-Kink waves or Alfvénic waves propagating inside their multicomponent substructure, by interpreting the quasi-coherent behavior of all visible components presumably confined by a surrounding magnetic envelop. We concentrate the analysis on the taller CaII spicules more relevant for coronal heights and easier to measure. Two-dimensional velocity maps of proper motion were computed for the first time using a correlation tracking technique based on FFTs and cross-correlation function with a 2nd-order-accuracy Taylor expansion. Highly processed images with the popular mad-max algorithm were first prepared to perform this analysis. The locations of the peak of the cross-correlation function were obtained with subpixel accuracy. Results. The surge-like behavior of solar polar region spicules supports the untwisting multicomponent interpretation of spicules exhibiting helical dynamics. Several tall spicules are found with (i) upward and downward flows that are similar at lower and middle levels, the rate of upward motion being slightly higher at high levels; (ii) the left-and righthand velocities are also increasing with height; (iii) a large number of multicomponent spicules show shearing motion of both left-and righthanded senses occurring simultaneously, which might be understood as twisting (or untwisting) threads. The number of turns depends on the overall diameter of the structure made of components and changes from at least one turn for the smallest structure to at most two or three turns for surge-like broad structures. The curvature along the spicule corresponds to a low turn number similar to a transverse kink mode oscillation along the threads.

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Wavelet analysis of solar macro-spicule recurrences

Cited by 15 publications

References 17 publications

A statistical analysis of the SOT-Hinode observations of solar spicules and their wave-like behavior

A statistical analysis of the SOT-Hinode observations of solar spicules and their wave-like behavior

Increasing the Fine Structure Visibility of the Hinode SOT Ca ii H Filtergrams

Alfvénic waves in polar spicules

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