Bimodal Distribution of Area-Weighted Latitude of Sunspots And Solar North-South Asymmetry

We study the latitudinal distribution of sunspots observed from 1874 to 2009 using the center-of-latitude (COL). We calculate COL by taking the area-weighted mean latitude of sunspots for each calendar month. We then form the latitudinal distribution of COL for the sunspots appearing in the northern and southern hemispheres separately, and in both hemispheres with unsigned and signed latitudes, respectively. We repeat the analysis with subsets which are divided based on the criterion of which hemisphere is dominant for a given solar cycle. Our primary findings are as follows: (1) COL is not monotonically decreasing with time in each cycle. Small humps can be seen (or short plateaus) around every solar maxima. (2) The distribution of COL resulting from each hemisphere is bimodal, which can well be represented by the double Gaussian function. (3) As far as the primary component of the double Gaussian function is concerned, for a given data subset, the distributions due to the sunspots appearing in two different hemispheres are alike. Regardless of which hemisphere is magnetically dominant, the primary component of the double Gaussian function seems relatively unchanged. (4) When the northern (southern) hemisphere is dominant the width of the secondary component of the double Gaussian function in the northern (southern) hemisphere case is about twice as wide as that in the southern (northern) hemisphere. (5) For the distribution of the COL averaged with signed latitude, whose distribution is basically described by a single Gaussian function, it is shifted to the positive (negative) side when the northern (southern) hemisphere is dominant. Finally, we conclude by briefly discussing the implications of these findings on the variations in the solar activity.Comment: Accepted for publication in New Astronom

Possible identification of precursor ELF signals on recent EQs that occurred close to the recording station

The Lithospheric–Atmospheric–Ionospheric Coupling (LAIC) mechanism stands as the leading model for the prediction of seismic activities. It consists of a cascade of physical processes that are initiated days before a major earthquake. The onset is marked by the discharge of ionized gases, such as radon, through subterranean fissures that develop in the lead-up to the quake. This discharge augments the ionization at the lower atmospheric layers, instigating disturbances that extend from the Earth’s surface to the lower ionosphere. A critical component of the LAIC sequence involves the distinctive perturbations of Extremely Low Electromagnetic Frequencies (ELF) within the Schumann Resonances (SR) spectrum of 2 to 50 Hz, detectable days ahead of the seismic event. Our study examines 10 earthquakes that transpired over a span of 3.5 months—averaging nearly three quakes monthly—which concurrently generated 45 discernible potential precursor seismic signals. Notably, each earthquake originated in Southern Greece, within a radius of 30 to 250 km from the observatory on Mount Parnon. Our research seeks to resolve two important issues. The first concerns the association between specific ELF signals and individual earthquakes—a question of significant importance in seismogenic regions like Greece, where earthquakes occur frequently. The second inquiry concerns the parameters that determine the detectability of an earthquake by a given station, including the requisite proximity and magnitude. Initial findings suggest that SR signals can be reliably linked to a particular earthquake if the observatory is situated within the earthquake’s preparatory zone. Conversely, outside this zone, the correlation becomes indeterminate. Additionally, we observe a differentiation in SR signals based on whether the earthquake took place over land or offshore. The latter category exhibits unique signal behaviors, potentially attributable to the water layers above the epicenter acting as a barrier to the ascending gases, thereby affecting the atmospheric–ionospheric ionization process

Anthropogenic Noise and Its Footprint on ELF Schumann Resonance Recordings

A set of various short artificial disturbances from rifle firings, car engine operation, car radio, shakings of the apparatus, etc., were generated deliberately near our ELF recording stations in order to identify their footprint on the recordings of atmospheric electromagnetic radiation in the Schumann resonance (SR) band (from about 2–50 Hz). Such disturbances simulate anthropogenic noises from hunters, hikers, campers, etc., which may occur in a remote-isolated ELF recording station. We expect that our work will assist fellow scientists to differentiate between artificial signals created from anthropogenic activity and real signals attributable to geophysical phenomena

Seismicity Precursors and Their Practical Account

Earthquakes (EQs) are the most unpredictable and damaging natural disasters. Over the last hundred years, the scientific community has been engaged in an intense endeavor to attain a confident and secure method of seismic activity forecasting. So far, despite these efforts, no fully validated method for predicting EQs has been established. However, research over the last thirty years has documented a substantial number of seismic precursor phenomena, the correct evaluation and application of which may pave the way for the development of a reliable EQ prediction method in the near future. Most documented seismic precursors belong to the rapidly evolving field of electro-seismology, while a smaller subset falls within the traditional domain of classical seismology and geophysics. This article aims to compile, classify, and assess the most well-documented precursors while also proposing a preliminary framework for their more effective application

Latitudinal and solar-cycle dependence of the interplanetary magnetic field predominant polarity

A study of the predominant interplanetary magnetic field (IMF) polarity is made, for the time period 1957-1977. The examination of the mean positive and negative sector width for time periods (semesters) for which the Earth was in northern and southern heliolatitudes shows that the predominant polarity for every semester follows, up to a certain extent, the Rosenberg-Coleman effect. However, the statistical support is not satisfactory. The same conclusion was pointed out by a similar study of data grouped over various phases of the solar cycle. Additionally the relative frequency of positive (negative) IMF polarity days, appeared over a mean solar rotation, shows that the general pattern of the mean IMF has a tendency to reoccur in the homologous (corresponding) phases of different solar cycles. © 1982 D. Reidel Publishing Company

Προσδιορισμός ποιοτικών χαρακτηριστικών σε δείγματα ελαιόλαδου βάσει του ευρωπαϊκού κανονισμού 2568/91

Σκοπός της εργασίας είναι ο προσδιορισμός της ποσοστιαίας αναλογίας των λιπαρών οξέων σε δείγματα ελαιόλαδου με χρήση αέριας χρωματογραφίας με ανιχνευτή ιονισμού φλόγας (GC-FID) και στη συνέχεια η σύγκριση των αποτελεσμάτων και αντιστοίχιση τους με τα ποιοτικά χαρακτηριστικά του ελαιόλαδου, όπως και η αντιστοίχιση του προφίλ των λιπαρών οξέων με την κατηγορία του δείγματος. Τα εκατό δείγματα που χρησιμοποιήθηκαν για τη μελέτη αυτή προέρχονται από διάφορες ελαιοπαραγωγικές περιοχές της Ελλάδας και εξετάστηκαν αρχικά ως προς τις βασικές ποιοτικές παραμέτρους τους, όπως ο βαθμός οξύτητας, ο αριθμός υπεροξειδίων και τα οργανοληπτικά χαρακτηριστικά. Έπειτα εξετάστηκε στα δείγματα αυτά, η ποσοστιαία αναλογία των λιπαρών οξέων με χρήση αέριας χρωματογραφίας με ανιχνευτή ιονισμού φλόγας (GC-FID). Στη συνέχεια έγινε στατιστική ανάλυση των αποτελεσμάτων και συσχέτιση του προφίλ των λιπαρών οξέων με το βαθμό οξύτητας, τον αριθμό υπεροξειδίων, τα οργανοληπτικά χαρακτηριστικά, την ποικιλία της ελιάς, την περιοχή καλλιέργειας, την υψομετρική θέση, το σύστημα εκχύλισης στο ελαιοτριβείο, τον τύπο καλλιέργειας καθώς και το χρονικό διάστημα που μεσολάβησε από τη συγκομιδή του καρπού ως την ελαιοποίηση. Τέλος, προτάθηκαν τρεις λόγοι λιπαρών οξέων, ένας για κάθε ποικιλία, που μπορούν να χρησιμοποιηθούν για την αναγνώριση δειγμάτων με βάση το προφίλ λιπαρών οξέων.The purpose of this study is to determine the percentages fatty acids in olive oil samples using gas chromatography with flame-ionization detector (GC-FID) and then to compare the results and match them with the quality characteristics of olive oil, as well as to match the fatty acids profile with the samples category. The one hundred samples used for this study came from various oil-producing regions of Greece and were initially examined for their basic quality parameters, such as degree of free acidity, peroxides and organoleptic characteristics. The percentages of fatty acids were then examined in these samples using gas chromatography with flame-ionization detector (GC-FID). Then the statistical analysis of the results was performed, so was the correlation of the fatty acids profile with the degree of acidity, the peroxides, the organoleptic characteristics, the olive tree variety, the cultivation area, the altitude, the extraction system in the mill, the type of cultivation as well and the time interval between the harvest of the fruit and the extraction. Finally, three fatty acid ratios were proposed, one for each variety, that can be used to identify samples based on fatty acids profil