M-Class Solar Flares in Solar Cycles 23 and 24: Properties and Space Weather Relevance

A comprehensive statistical analysis on the properties and accompanied phenomena of all M-class solar flares (as measured in soft X-rays) in the last two solar cycles (1996–2019) is presented here with a focus on their space weather potential. The information about the parent active region and the underlying sunspot (Hale) type is collected for each case, where possible, in order to identify photospheric precondition as precursors for the solar flare eruption or confinement. Associations with coronal mass ejections, solar energetic particles, and interplanetary radio emissions are also evaluated and discussed as possible proxies for flare eruption and subsequent space weather relevance. The results show that the majority (∼80%) of the analyzed M-class flares are of β, β-γ, and β-γ-δ magnetic field configuration. The M-class population of flares is accompanied by CMEs in 41% of the cases and about half of the flare sample has been associated with radio emission from electron beams. A much lower association (≲10%) is obtained with shock wave radio signatures and energetic particles. Furthermore, a parametric scheme is proposed in terms of occurrence rates between M-class flares and a variety of accompanied solar phenomena as a function of flare sub-classes or magnetic type. This study confirms the well-known reduced but inevitable space weather importance of M-class flares.

Mössbauer Studies of Narrow Fractions of Fly Ash Formed after Combustion of Ekibastuz Coal

Nuclear gamma-resonance spectroscopy on 57Fe nuclei, X-ray diffraction, and scanning electron microscopy have been used to study the narrow fractions of fly ash formed after combustion of the Ekibastuz coal. Two groups of samples of magnetic (ferrospheres) and non-magnetic type have been separated by granulometric and magnetic separation. A number of regularities associated with the granules size of fly ash have been established. According to the data of Mössbauer spectroscopy, a decrease in the magnetically ordered contribution has been identified with the growth of the particle size. After magnetic separation, iron in ferrospheres was found mainly in the structure of Fe3O4/γ-Fe2O3 and α-Fe2O3. The dominant phase was Fe3O4 (60–77%), the amount of which decreases with the growth of the grain size. With the growth of the particle size, the ratio of [Fe]tetra/[Fe]octa positions occupancy in Fe3O4 approaches 0.5; the structure of magnetite tends to the stoichiometric composition. α-Fe was found in the composition of ferrospheres, and a mechanism of its formation was proposed. The main components of the non-magnetic fractions of fly ash are mullite, hercynite, and silicate glass.

Multiple CNN Variants and Ensemble Learning for Sunspot Group Classification by Magnetic Type

A solar active region is a source of disturbance for the Sun–terrestrial space environment and usually causes extreme space weather, such as geomagnetic storms. The main indicator of an active region is sunspots. Certain types of sunspots are related to extreme space weather caused by eruptive events such as coronal mass ejections or solar flares. Thus, the automatic classification of sunspot groups is helpful to predict solar activity quickly and accurately. This paper completed the automatic classification of a sunspot group data set based on the Mount Wilson classification scheme, which contains continuum and magnetogram images provided by the Solar Dynamics Observatory’s Helioseismic and Magnetic Imager SHARP data from 2010 May 1 to 2017 December 12. After applying some data preprocessing steps such as image cropping and data standardization, the features of magnetic type in the data are more obvious, and the amount of data is increased. The processed data are spliced into two frames of single-channel data for the neural network to perform 3D convolution operations. This paper constructs a variety of convolutional neural networks with different structures and numbers of layers, selects 10 models as representatives, and chooses XGBoost, which is commonly used in ensemble-learning algorithms, to fuse the results of independent classification models. We found that XGBoost is an effective way to fuse models, which is proved by the relatively balanced high scores in the three magnetic types. The accuracy of the ensemble model is above 92%. The F1 scores of the magnetic types of Alpha, Beta, and Beta-x reached 0.95, 0.91, and 0.82 respectively.

Dual fields of massive/massless gravitons in IR/UV completions

In the holographic picture, the Brout-Englert-Higgs (BEH) mechanism in [Formula: see text]-dimensional Yang–Mills theories is conjectured to provide a Higgs-like mechanism for gravity in [Formula: see text] dimensions, resulting in massive (or massless) gravitons in IR (or UV) completions. Accordingly, one could imagine dual (magnetic-type) fields of massive gravitons in the IR (low-energy) limit that are coupled to the curl of their own energy–momentum, as well as to the rotation of matter fields on large scales. This hypothesis, which might solve cosmological issues currently ascribed to dark matter and dark energy, needs to be examined by the future Laser Interferometer Space Antenna mission using observations of gravitational waves emitted from extragalactic sources.

ENERGY LOSSES OF A POINT MAGNETIC DIPOLE DUE TO INTERACTION WITH A MAGNETIZED PLASMA CYLINDER

In this work, the excitation problem of bulk-surface helicons by a point magnetic dipole moving in a vacuum parallel to the element of magnetized solid-state plasma cylinder is theoretically studied. The external magnetic field is directed parallel to the cylinder axis. The problem is solved in the magnetostatic approximation. It is shown that hybrid modes of the magnetic type with large values of the azimuthal mode index and one field variation along the radius are most efficiently excited at nonrelativistic velocities of magnetic dipole.

Exploring Consumer Reviews for Men’s Fashion Accessories in Online Purchase Platforms Using Sentiment Analysis

The recent trend in the Indian menswear market has witnessed the infusion of western styles. Result of this is a promising market in India for men’s fashion accessories like caps, sunglasses, bracelets, rings etc. One among the accessories is earrings for man. This product category has got line extensions like studs, hoops, non-piercing magnetic type and piercing studs etc. Keeping in consideration the whooping growth of the men’s earrings market in the online purchase platforms, this study is done with an objective to explore the reviews for this product category to arrive at some insights. For this study descriptive research design has been adopted. Using the scraper tool in Python software, the data (user’s reviews for men’s earrings) was collected from the top two online vendors in India (Amazon and Flipkart). Sentiment analysis is done with R software using the text analytical package “sentiment”. Then the sentiment scores was deployed in ANOVA to test for any significant differences in star ratings and the product variant purchased by the customer taking the Comment Sentiment Scores and Title Sentiment Score. The results have shown that there is a significant difference between the star ratings and Comment Sentiment Scores, Title Sentiment Score. Bivariate correlation is applied to test the relationship between Comment Sentiment Score, Title Sentiment Score and star ratings. The result revealed that star ratings, Comment Sentiment Scores and Title Sentiment Score have a significant relationship with each other.

Mathematical Model of the Process of Pallet Movement Along the Magnetic Type Centrifugal Brake Roller

One of the main elements of safe operation of gravity flow racks used in pallet racks is a brake roller. The most promising design is a centrifugal brake roller of magnetic (eddy current) type. The principle of operation of such rollers is based on the laws of electromagnetic induction and involves the deceleration of a conductor moving in a magnetic field, due to the interaction of eddy currents (or Foucault currents) arising in the volume of the conductor, with an external magnetic field. The mathematical model of the process of pallet movement along a centrifugal brake roller of magnetic type is developed in the article. The equation of the speed of movement of the pallet along the centrifugal brake roller of magnetic type is obtained. Comparative analysis of the speed of movement of a pallet along centrifugal and disc brake rollers of magnetic type is carried out.