Temporal and Periodic Variations of Sunspot Counts in Flaring and Non-Flaring Active Regions

We analyzed temporal and periodic variations of sunspot counts (SSCs) in flaring (C-, M-, or X-class flares), and non-flaring active regions (ARs) for nearly three solar cycles (1986 through 2016). Our main findings are as follows: i) temporal variations of monthly means of the daily total SSCs in flaring and non-flaring ARs behave differently during a solar cycle and the behavior varies from one cycle to another; during Solar Cycle 23 temporal SSC profiles of non-flaring ARs are wider than those of flaring ARs, while they are almost the same during Solar Cycle 22 and the current Cycle 24. The SSC profiles show a multi-peak structure and the second peak of flaring ARs dominates the current Cycle 24, while the difference between peaks is less pronounced during Solar Cycles 22 and 23. The first and second SSC peaks of non-flaring ARs have comparable magnitude in the current solar cycle, while the first peak is nearly absent in the case of the flaring ARs of the same cycle. ii) Periodic variations observed in the SSCs profiles of flaring and non-flaring ARs derived from the multi-taper method (MTM) spectrum and wavelet scalograms are quite different as well, and they vary from one solar cycle to another. The largest detected period in flaring ARs is \(113\pm 1.6~\mbox{days}\) while we detected much longer periodicities (\(327\pm 13\), \(312 \pm 11\), and \(256\pm 8~\mbox{days}\)) in the non-flaring AR profiles. No meaningful periodicities were detected in the MTM spectrum of flaring ARs exceeding \(55\pm 0.7~\mbox{days}\) during Solar Cycles 22 and 24, while a \(113\pm 1.3~\mbox{days}\) period was detected in flaring ARs of Solar Cycle 23. For the non-flaring ARs the largest detected period was only \(31\pm 0.2~\mbox{days}\) for Cycle 22 and \(72\pm 1.3~\mbox{days}\) for the current Cycle 24, while the largest measured period was \(327\pm 13~\mbox{days}\) during Solar Cycle 23.     

Le Fe XII dans la couronne d'émission

Résumé En supposant le FeXII réduit à 16 niveaux d'énergie, nous avons étudié l'intensité relative de 21 raies spectrales en fonction des deux paramètres température et densité électronique. Les résultats sont brièvement discutés, et sont résumés dans les Figures 1–21.

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Assuming that FeXII is reduced to 16 energy levels, we have computed the relative intensities of 21 spectral lines as a function of two parameters, temperature and electron density. Results are briefly discussed and summarized in Figures 1–21.

     

Calcul des probabilités de transition pour divers états excités du Fe XII

Résumé On a calculé les probabilités de transition pour les raies interdites ou permises entre les états (3p²3d-3p³), (3p²4s-3p³), (3s3p⁴-3s²3p³), (3p²4d-3P³) du FeXII. Les niveaux d'énergie ²D_3/2, ²D_5/2, ²P_1/2, ²P_3/2 ont été obtenus par extrapolation le long de la séquence isoélectronique P1. On discute brièvement les effets d'un écart aux conditions de couplage L-S dus aux interactions spin-orbite et de configuration.

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Transition probabilities have been computed for forbidden or permitted lines within the (3p²3d-3p³), (3p²4s-3p³), (3s3p⁴-3s²3p³), (3p²4d-3p³) configurations in FeXII. Energy levels ²D_3/2, ²D_5/2, ²P_1/2, ²P_3/2 have been predicted by extrapolation along the isoelectronic sequence P1. The effects of departures from L-S coupling due to spin-orbit and configuration interaction are briefly discussed.

     

A brief history of the solar oblateness. A review

We hereby present a review on solar oblateness measurements. By emphasizing historical data, we illustrate how the discordance between experimental results can lead to substantial improvements in the building of new technical apparatus as well as to the emergence of new ideas to develop new theories. We stress out the need to get accurate data from space to enhance our knowledge of the solar core in order to develop more precise ephemerids and ultimately build possible new gravitational theories.     

Variability of the solar shape (before space dedicated missions)

Shrinking or expansion of the solar shape and irradiance variations are ultimately related to solar activity. We give here a review on existing ground-based or space solar radius measurements, extending the concept to shape changes. We show how helioseismology results allow us to look at the variations below the surface, where changes are not uniform, putting in evidence a new shallow layer, the leptocline, which is the seat of solar asphericities, radius variations with the 11-yr cycle and the cradle of complex physical processes: partial ionization of the light elements, opacities changes, superadiabaticity, strong gradient of rotation and pressure. Based on such physical grounds, we show why it is important to get accurate measurements from scheduled dedicated space missions: PICARD, SDO, DynaMICCS, ASTROMETRIA, SPHERIS. Such measurements will provide us a unique opportunity to study in detail the relationship between global solar properties and changes in the Sun's interior.     

On the stability of the 11-year solar cycle period (and a few others)

The existence of an 11.1-yr periodic variation in the sunspot number record has been recognized for many years; however, periodicities other than this remain questionable. Power spectral analysis of the International sunspot number is performed and the results are compared with those for the same period using values that were taken randomly inside the error bars. The findings are that only a few periodicities show noticeable peaks. These include periodicities of 8.49, 10.01, 10.58, 11.10, 12.50, 58.50, and 97.20 yr. On the basis of these seven periodicities, one can loosely simulate the observable sunspot record (r = 0.75). We find that discrepancies in number and value of periodicities with other authors appear to be related to the length of the sunspot record used in the analysis and to the occurrence of 0.3-yr windows around the inferred periodicities.     

Sur la détermination du rapport d'intensité des raies infrarouges de l'ion Fe xiii

Résumé Le rapport des deux raies infrarouges 10747 Å et 10798 Å de l'ion Fe xiii a été étudié d'une manière théorique et observationnelle. Les résultats et la discussion des deux points de vue sont résumés par des tableaux. A partir du rapport mesuré des deux raies, nous avons donné une variation de la densité électronique avec le rapport de dilution, incluant les mécanismes de collisions protoniques dans la résolution des équations d'équilibre (selon la méthode de Chevalier et Lambert). Les plaques ont été obtenues le 25 mai 1971, sur deux latitudes héliographiques non perturbées.

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The ratio of the two infrared lines 10747 Å and 10798 Å of Fe xii is studied from a theoretical and observational point of view. The results and the discussion of the two determinations are summarized into two tables. Arising from a measured ratio of the two lines, a variation of the electron density as a function of dilution factor is given, taking into account the proton impact's mechanism in the resolution of excitation equilibrium (as presented by Chevalier and Lambert). The plates have been recorded the 25th of May 1971, for two unperturbed heliographic latitudes.

     

Tables pour determiner la concentration d'atomes dans un etat donne: Ions coronaux interessants

Résumé Les populations des niveaux excités des ions coronaux suivent avec une très bonne approximation une loi analytique du type a × N _e ^b, où N _e est la densité électronique du milieu et où a et b sont des coefficients dépendant seulement de la distance du bord et de la température. Cette forme est particulièrement souple d'emploi pour l'interprétation des mesures d'intensités des raies démission coronales.Les coefficients a et b présentés ici, ont été déterminés à partir des résultats de nombreux auteurs, et portent sur les niveaux intervenant dans les transitions responsables des raies observées dans le domaine visible et infra-rouge du spectre coronal concernant les ions: Fe x, xi, xiii, xiv, xv; Ca xiii, xv; Ni xii, xiii, xv, xvi et A xiv. L'examen des coefficients b permet notamment de sélectionner les raies les plus sensibles à la densité électronique.

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The populations of the excited levels of coronal ions follow with very great accuracy an analytical law of the type a × N _e ^b, where N _e is the electron density of the medium and where a and b are only temperature and solar limb distance dependant coefficients. This form is particularly well adapted for the interpretation of the intensities measurements of coronal emission lines.The coefficients a and b here presented have been determined according to the results of various authors, and deal with the levels concerning the transitions responsible for the lines observed in the visible and infrared coronal field, and chiefly bear on the following ions: Fe x, xi, xiii, xiv, xv; Ca xiii, xv; Ni xii, xiii, xv, xvi, and A xiv. The most sensitive lines to the electron density can be selected thanks to the examination of the coefficient b.

     

Revisiting the Solar Oblateness: Is Relevant Astrophysics Possible?

The measurement of solar oblateness has a rich history extending well back into the past. Until recently, its estimate has been actively disputed, as has its temporal dependence. Recent accurate observations of the solar shape gave cause for doubt, and so far only balloon flights or satellite experiments, such as those onboard SDO, seem to achieve the required sensitivity to measure the expected small deviations from sphericity. A shrinking or an expanding shape is ultimately linked to solar activity (likely not homologously with its change), as gravitational or magnetic fields, which are existing mechanisms for storing energy during a solar cycle, lead to distinct perturbations in the equilibrium solar-structure and changes in the diameter. It follows that a sensitive determination of the solar radius fluctuations might give information about the origin of the solar cycle. In periods of higher activity, the outer photospheric shape seems to become aspheric under the influence of higher-order multipole moments of the Sun, resulting both from the centrifugal force and the core rotation. An accurate determination of the shape of the Sun is thus one of the ways that we have now for peering into its interior, learning empirically about flows and motions there that would otherwise only be guessed at from theoretical considerations, developing more precise inferences, and ultimately building possible alternative gravitational theories.