A Comparison of Sparse and Non-sparse Techniques for Electric-Field Inversion from Normal-Component Magnetograms

An important element of 3D data-driven simulations of solar magnetic fields is the determination of the horizontal electric field at the solar photosphere. This electric field is used to drive the 3D simulations and inject energy and helicity into the solar corona. One outstanding problem is the localisation of the horizontal electric field such that it is consistent with Ohm’s law. Yeates (Astrophys. J.836(1), 131, 2017) put forward a new “sparse” technique for computing the horizontal electric field from normal-component magnetograms that minimises the number of non-zero values. This aims to produce a better representation of Ohm’s law compared to previously used “non-sparse” techniques. To test this new approach we apply it to active region (AR) 10977, along with the previously developed non-sparse technique of Mackay, Green, and van Ballegooijen (Astrophys. J.729(2), 97, 2011). A detailed comparison of the two techniques with coronal observations is used to determine which is the most successful. Results show that the non-sparse technique of Mackay, Green, and van Ballegooijen (2011) produces the best representation for the formation and structure of the sigmoid above AR 10977. In contrast, the Yeates (2017) approach injects strong horizontal fields between spatially separated, evolving magnetic polarities. This injection produces highly twisted unphysical field lines with significantly higher magnetic energy and helicity. It is also demonstrated that the Yeates (2017) approach produces significantly different results that can be inconsistent with the observations depending on whether the horizontal electric field is solved directly or indirectly through the magnetic vector potential. In contrast, the Mackay, Green, and van Ballegooijen (2011) method produces consistent results using either approach. The sparse technique of Yeates (2017) has significant pitfalls when applied to spatially resolved solar data, where future studies need to investigate why these problems arise.

Analysis of the livewire software application on students’ learning understanding and motivation on ohm’s law concepts

The study aimed to analyze the conceptual understanding and motivation to learning physics in schools with the help of livewire software. An experimental method with a post-test-only nonequivalent control group design was used to examine Ohm’s Law. The sample for the study consisted of a control class with 36 students and an experimental group comprising 37 learners drawn from a population of 145 through random sampling. Data collection tools used were tests and questionnaires to collect data, which was analyzed using the non-parametric statistics technique. The results showed that the livewire software made students’ understanding of Ohm’s Law concepts better compared to learning without the help of the software. Livewire software can motivate students to study Ohm’s Law.

Use of filtration and electricity analogy in simulation of underflooding protection in urban construction

Introduction. The fight against underflooding remains an urgent problem. The application of the analogy between water filtration and electric current has the goal of protecting the environment, built-up areas and, in particular, highways in cities from underflooding. Writing Ohm’s law similarly to Darcy’s filtration law, we achieve a better match to their analogy. This, in turn, makes it possible to develop new technologies for protection against underflooding in urban construction, for example, electroosmotic dewatering and its modeling. Such technologies make it possible to drain clayey soils.Methods and materials. Darcy’s law, Ohm’s law and the law of electroosmotic filtration are considered together. A methodology for modelling construction dewatering is given, taking into account the combined effect of the two physical laws of water filtration and electroosmosis, optimally combining the high-altitude geometric arrangement of drainage bases and contact electrodes. The options for draining clay soil under the action of an electric field are presented. With the combined use of gravitational forces and electric direct current forces in the drained soil, the total filtration rate is the sum of the Darcy’s law component and another component of the water velocity – electroosmotic filtration. An additional feature of joint modelling in a porous medium of water filtration and electroosmosis is that the mass of the water-resistant part of the soil and its part related to the dielectric may not coincide. This complexity of the model is overcome by dividing it into modules, which can then be combined in compliance with the balance principle, stitching modules along the boundaries. To continue the scientific discussion, a short but informative overview of international publications on the topic under consideration is given.Discussion. The methodology for complex calculation and modelling of the joint processes of water filtration in soils, the flow of electric current and electroosmotic filtration can find useful application in the development of effective protection against underflooding in urban construction. a sequence of algorithmic modelling steps is recommended. initially, it is recommended to run rough spreadsheet simulations on personal computers and mobile phones. next, a different modelling approach should be applied. based on the initial rough models of the previous step, it is necessary to write the algorithms in the programming language. the compiled model of the investigated filtration and electroosmosis processes will significantly increase the reliability of the design of protection against underflooding.conclusion. a comparison is made of the joint use of construction dewatering means of different physical essence, with simultaneous processes of gravitational filtration of underground water and passing a direct electric current through the drained soil, which causes an additional effect of electroosmosis. it is proposed to apply in a new way the analogy of water filtration and electric current in order to achieve more effective results of engineering activities by modeling protection against underflooding of building areas, ensuring the safety of urban construction when the level of groundwater rises.