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.
A new software (Soonspot) for the determination of the heliographic coordinates and areas of sunspots from solar images is presented. This program is very user-friendly and the accuracy of its ...results has been checked by using solar images provided by the Debrecen Photoheliographic Data (DPD). Due to its applicability in the studies of historical solar observations, the program has been used to analyze the solar drawings carried out by Hevelius in the 17th century.
A new normalized sunspot-area series has been reconstructed from the series obtained by the Royal Greenwich Observatory and other contemporary institutions for the period 1874 – 2008 and the area ...series compiled by De la Rue, Stewart, and Loewy from 1832 to 1868. Since the two sets of series do not overlap in time, we used the new version of sunspot index number (Version 2) published by Sunspot Index and Long-term Solar Observations (SILSO) as a link between them. We also present a spectral analysis of the normalized-area series in search of periodicities beyond the well-known solar cycle of 11 years and a study of the Waldmeier effect in the new version of sunspot number and the sunspot-area series presented in this study. We conclude that while this effect is significant in the new series of sunspot number, it has a weak relationship with the sunspot-area series.
In this paper we analyze a small collection of sunspot drawings made at the Astronomical Observatory of the Spanish Navy in the period from April 1, 1884 to August 18, 1884. We calculate the area and ...the heliographic coordinates of the observed sunspots. From these coordinates, we obtain the solar rotation rate in this period. Finally, we compare our results with the data recorded by the Royal Greenwich Observatory.
Solar rotation rate has been measured using the sunspot positions recorded by W.C. Bond during the period 1847 – 1849 at the Harvard College Observatory. From the drawings carried out by Bond we have ...selected the sunspots and groups of sunspots with more reliable positions presented in three or more drawings on successive days. We have calculated from the positions of the selected sunspots (41 in total) a synodic rotation rate of
ω
=(12.92±0.08)−(1.5±1.0)sin
2
φ
degrees/day, where
φ
is the heliographic latitude. This rate, although slightly lower, is similar to the actual solar rotation rate, confirming no important changes in the solar rotation during the last 160 years.
A modified application of the variance method, using the pseudo‐Voigt function as a good approximation to the X‐ray diffraction profiles, is proposed in order to obtain microstructural quantities ...such as the mean crystallite size and root‐mean‐square (r.m.s.) strain. Whereas the variance method in its original form is applicable only to well separated reflections, this technique can be employed in the cases where there is line‐profile overlap. Determination of the mean crystallite size and r.m.s. strain for several crystallographic directions in a nanocrystalline cubic sample of 9‐YSZ (yttria‐stabilized zirconia) has been performed by means of this procedure.
Valuable information about the evolution of solar activity is recorded in early sunspot drawings, especially during 17th–19th centuries. In this context, we have developed a computer program to ...analyze historical drawings showing the trajectories of sunspots across the solar disk. As an example, we have analysed the drawings published in the book
De heliometri structura et usu by
Zucconi (1760). These drawings span the period from April 1754 to June 1760. We present the Butterfly diagram for those years. The ending of solar cycle 0 and the beginning of solar cycle 1 are clearly noted in this diagram.
An analytical model for the determination of crystallite size and crystal lattice microstrain distributions in nanocrystalline (nc) materials by X-ray diffractometry (XRD) is presented. It entails ...generalizing the variance method to establish analytically the connection between the variance coefficients of the physically broadened XRD peaks and the characteristic parameters of explicit distributions of crystallite sizes and crystal lattice microstrains, which results in a more detailed characterization of the nc-materials. The proposed model is generic in nature and has the potential to be used under the assumption of different mathematical functions for the two distributions, which suggests that it may have an important role to play in the characterization of nc-materials. Nevertheless, the specialization to the case of nc-materials with log-normal crystallite size distribution and three typical types of lattice microstrains is used as an illustration and to formulate explicit analytical expressions of interest. Finally, the usefulness of the proposed model is demonstrated on standard XRD profiles.
We have developed a novel, analytical model for the determination of grain size distributions in nanocrystalline (nc) materials with low internal stresses by X-ray diffractometry (XRD). The model ...assumes explicitly that the XRD peaks are pseudo-Voigtian and that the grain size distributions are lognormal, both of which are assumptions amply supported by the experimental evidence. It was found analytically that the grain size dispersion depends on the shape of the XRD peaks only, whereas the grain size median depends on both the shape and width of the XRD peaks. In addition, the theoretical predictions resulting from the model were validated using standard XRD peaks obtained by computer simulation from first principles. Particular emphasis is given to the discussion of the validity limits of the model, and to the analysis of the influence of the characteristics of the grain size distributions on the nature of the XRD peaks. We then show how to calculate the average and apparent grain sizes from the grain size distribution determined with the model, and how this compares with the Scherrer method. Implications for the characterization of (undistorted and distorted) nc-materials are indicated, and a case study of an nc-powder of cubic ZrO
2 is presented. The application of the model itself is simple, involving only the fit of a pseudo-Voigt function to a single XRD peak followed by the use of two equations. This suggests that the model may have an important role to play in the characterization of nc-materials.
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