We propose a phenomenological technique for modelling the emergence of active regions within a three-dimensional, kinematic dynamo framework. By imposing localized velocity perturbations, we create ...emergent flux tubes out of toroidal magnetic field at the base of the convection zone, leading to the eruption of active regions at the solar surface. The velocity perturbations are calibrated to reproduce observed active region properties (including the size and flux of active regions, and the distribution of tilt angle with latitude), resulting in a more consistent treatment of flux-tube emergence in kinematic dynamo models than artificial flux deposition. We demonstrate how this technique can be used to assimilate observations and drive a kinematic three-dimensional model, and use it to study the characteristics of active region emergence and decay as a source of poloidal field. We find that the poloidal components are strongest not at the solar surface, but in the middle convection zone, in contrast with the common assumption that the poloidal source is located near the solar surface. We also find that, while most of the energy is contained in the lower convection zone, there is a good correlation between the evolution of the surface and interior magnetic fields. PUBLICATION ABSTRACT
We test recent claims that the polar field at the end of Cycle 23 was weakened by a small number of large, abnormally oriented regions, and investigate what this means for solar cycle prediction. We ...isolate the contribution of individual regions from magnetograms for Cycles 21, 22, and 23 using a 2D surface flux transport model, and find that although the top ∼10% of contributors tend to define sudden large variations in the axial dipole moment, the cumulative contribution of many weaker regions cannot be ignored. To recreate the axial dipole moment to a reasonable degree, many more regions are required in Cycle 23 than in Cycles 21 and 22 when ordered by contribution. We suggest that the negative contribution of the most significant regions of Cycle 23 could indeed be a cause of the weak polar field at the following cycle minimum and the low-amplitude Cycle 24. We also examine the relationship between a region's axial dipole moment contribution and its emergence latitude, flux, and initial axial dipole moment. We find that once the initial dipole moment of a given region has been measured, we can predict the long-term dipole moment contribution using emergence latitude alone.
An analysis of the sunspot observations made by Hevelius during 1642-1645 is presented. These records are the only systematic sunspot observations just before the Maunder Minimum (MM). We have ...studied different phenomena meticulously recorded by Hevelius after translating the original Latin texts. We reevaluate the observations of sunspot groups by Hevelius during this period and obtain an average value 7% greater than that calculated from his observations given in the current group database. Furthermore, the average of the active day fraction obtained in this work from Hevelius's records previous to the MM is significantly greater than the solar activity level obtained from Hevelius's sunspot observations made during the MM (70% versus 30%). We also present the butterfly diagram obtained from the sunspot positions recorded by Hevelius for the period 1642-1645. It can be seen that no hemispheric asymmetry exists during this interval, in contrast with the MM. Hevelius noted a ∼3-month period that appeared to lack sunspots in early 1645 that gave the first hint of the impending MM. Recent studies claim that the MM was not a grand minimum period, speculating that astronomers of that time, due to the Aristotelian ideas, did not record all sunspots that they observed, producing thus an underestimation of the solar activity level. However, we show that the good quality of the sunspot records made by Hevelius indicates that his reports of sunspots were true to the observations.
Abstract
Christoph Scheiner was one of the most outstanding astronomers in the history of sunspot observations. His book,
Rosa Ursina
, is the reference work regarding the study of the earliest ...sunspot records. The sunspot observations compiled by Scheiner in
Rosa Ursina
and
Prodomus
, including records made by other observers, forms one of the main references of the observations known for that period—particularly around the 1620s. Thus, his work is crucial to determine the solar activity level of the first solar cycles of the telescopic era. The number of sunspot groups recorded in Scheiner’s documentary sources has been included in the existing sunspot group number databases. However, we have detected significant errors in the number of groups currently assigned to Scheiner’s records. In this work, we reanalyze the information in Scheiner’s source documents. Consequently, the standard 11 yr solar cycle shape for the second solar cycle of the telescopic era, which is not clear in previous studies, now becomes evident. In addition, the highest daily number of groups recorded during this cycle (eight groups) is 20% less than in the one included in the existing sunspot group number databases. Using the hypergeometrical probability distribution, we find that solar minima in 2008–2009 and 2018–2019 are comparable to the most probable solar activity level of the minimum around 1632. In particular, the estimated lower limit for the solar activity in 1632 is even comparable with the solar activity level in 2008 and 2018.
We report progress on the ongoing recalibration of the Wolf sunspot number (SN) and group-sunspot number (GN) following the release of version 2.0 of SN in 2015. This report constitutes both an ...update of the efforts reported in the 2016 Topical Issue of Solar Physics and a summary of work by the International Space Science Institute (ISSI) International Team formed in 2017 to develop optimal SN and GN reconstruction methods while continuing to expand the historical sunspot-number database. Significant progress has been made on the database side while more work is needed to bring the various proposed SN and (primarily) GN reconstruction methods closer to maturity, after which the new reconstructions (or combinations thereof) can be compared with (a) “benchmark” expectations for any normalization scheme (e.g., a general increase in observer normalization factors going back in time), and (b) independent proxy data series such as F10.7 and the daily range of variations of Earth’s undisturbed magnetic field. New versions of the underlying databases for SN and GN will shortly become available for years through 2022 and we anticipate the release of the next versions of these two time series in 2024.
Accurate prediction of solar activity calls for precise calibration of solar cycle models. Consequently we aim to find optimal parameters for models which describe the physical processes on the solar ...surface, which in turn act as proxies for what occurs in the interior and provide source terms for coronal models. We use a genetic algorithm to optimize surface flux transport models using National Solar Observatory (NSO) magnetogram data for Solar Cycle 23. This is applied to both a 1D model that inserts new magnetic flux in the form of idealized bipolar magnetic regions, and also to a 2D model that assimilates specific shapes of real active regions. The genetic algorithm searches for parameter sets (meridional flow speed and profile, supergranular diffusivity, initial magnetic field, and radial decay time) that produce the best fit between observed and simulated butterfly diagrams, weighted by a latitude-dependent error structure which reflects uncertainty in observations. Due to the easily adaptable nature of the 2D model, the optimization process is repeated for Cycles 21, 22, and 24 in order to analyse cycle-to-cycle variation of the optimal solution. We find that the ranges and optimal solutions for the various regimes are in reasonable agreement with results from the literature, both theoretical and observational. The optimal meridional flow profiles for each regime are almost entirely within observational bounds determined by magnetic feature tracking, with the 2D model being able to accommodate the mean observed profile more successfully. Differences between models appear to be important in deciding values for the diffusive and decay terms. In like fashion, differences in the behaviours of different solar cycles lead to contrasts in parameters defining the meridional flow and initial field strength.
In this paper we address a discrepancy between the surface flux evolution in a 3D kinematic dynamo model and a 2D surface flux transport model that has been closely calibrated to the real Sun. We ...demonstrate that the difference is due to the connectivity of active regions to the toroidal field at the base of the convection zone, which is not accounted for in the surface-only model. Initially, we consider the decay of a single active region, firstly in a simplified Cartesian 2D model and subsequently the full 3D model. By varying the turbulent diffusivity profile in the convection zone, we find that increasing the diffusivity – so that active regions are more rapidly disconnected from the base of the convection zone – improves the evolution of the surface field. However, if we simulate a full solar cycle, we find that the dynamo is unable to sustain itself under such an enhanced diffusivity. This suggests that in order to accurately model the solar cycle, we must find an alternative way to disconnect emerging active regions, whilst conserving magnetic flux.
Abstract
A sunspot observation program was started at the end of the 19th century at the Stonyhurst College Observatory (hereafter SCO) by Father Perry, director of the observatory at that time. A ...digitization of the daily sunspot area series recorded in this observatory from 1886 to 1940 (with a gap between 1889 and 1897) is provided in this work. This depicts one of the oldest sunspot area series available. A comparison of this series with contemporary area series made in other observatories shows that SCO generally recorded larger areas than those in some of the observatories of that time such as, for example, the Royal Greenwich Observatory (RGO). Furthermore, SCO published a sunspot group catalog for the period 1921–1935. We provide a machine-readable version of this catalog. We compared the SCO group number series with other sunspot data obtained from other observatories. In this case, for example, the RGO systematically recorded more groups than the SCO. We compared SCO and RGO area distribution functions obtaining the calibration constant between both data sets. We also obtained the butterfly diagram from the group latitudes recorded by SCO and compared the percentages of group types computed from the SCO catalog with those from Valencia Observatory (following the Cortie morphological classification of sunspot groups), identifying their similarities and differences.
The study assessed microhardness, microleakage of Class I, and the degree of conversion of composite resins preheated at 55 °C. This in vitro study evaluated two nanofilled composite resins (NCR), ...Filtek™ P60 and Filtek™ Z350 XT, used in the restorations. The degree of conversion (DC) was determined by Raman spectroscopy; the study compared the vibrational bands of the residual unpolymerized methacrylate C=C stretching band at 1640 cm
−1
to the aromatic C–C stretching band at 1610 cm
−1
, used as an internal standard. Microleakage tests considered standard Class 1 cavities prepared on human premolars randomly divided. Preheating Filtek™ P60 and Filtek™ Z350 XT increased significantly VMH values (
p
= 0.0001). The highest microleakage occurred in preheated Filtek™ Z350 XT, while the lowest was in unheated Filtek™ P60. Unheated Filtek™ Z350 XT showed a significant increase of microleakage than unheated Filtek™ P60. (
p
= 0.024). Preheating of composite resins improved mechanical properties increasing DC and VMH. However, it also increases microleakage promoting bacterial penetration, secondary caries, marginal discoloration and hypersensitivity.
The research aims to evaluate short- and medium-term outcomes of patients treated using autologous matrix-induced chondrogenesis (AMIC) with a hyaluronic acid scaffold (Hyalofast, Anika Therapeutics, ...MA, USA) in grade IV chondral lesions according to the Outerbridge classification in the knee.
This is a multicentre, non-randomized, retrospective study conducted between 2017 and 2022. To determine the clinical outcome of the patients, the follow-up was done with the subjective International Knee Documentation Committee (IKDC) score, pre-surgery, and with a follow-up at 12, 24, and 32 months.
Fifty patients (28 female) with a mean age of 45.9 ± 12.7 years were recruited. The mean size of the lesion was 3.5 cm2, and the injuries located in the patella (30%) and trochlear groove (24%) were the most frequent. The total IKDC clinical score significantly increased from baseline to the 32 months of follow-up with a mean difference of 36.4 (95% CI, 29.1–43.7, p < 0.001). Besides, there was a statistically significant improvement in all categories of the IKDC (symptoms, sports activities, function, and activity of daily living) compared between pre-surgery and 24 and 32 months of follow-up. The patients younger than 45 years presented better clinical outcomes than older ones with a difference between medians of 10.40 (95% CI, 1.10–11.50, p = 0.0247), and a negative correlation was found between the 32-month IKDC score and the age. In addition, no statistically significant difference was found when comparing the last results of the IKDC between patients with and without associated surgical procedures or between patients with single and several lesions, neither nor between men and women. The level of satisfaction with the procedure of all the patients, on a score of 1–10, was on average 8 ± 1.5.
Results of this study indicate that patients who underwent the AMIC procedure with hyaluronic acid scaffold for the treatment of grade IV chondral lesions in the knee presented satisfactory results throughout the follow-up.
Level IV
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