Plasma injection into a solar coronal loop

Context. The details of the spectral profiles of extreme UV emission lines from solar active regions contain key information to investigate the structure, dynamics, and energetics of the solar upper atmosphere. Aims. We characterize the line profiles not only through the Doppler shift and intensity of the bulk part of the profile. More importantly, we investigate the excess emission and asymmetries in the line wings to study twisting motions and helicity. Methods. WeusearasterscanoftheInterfaceRegionImagingSpectrograph(IRIS)inanactive region. We concentrate on the Si iv line at 1394 {\AA} that forms just below 0.1 MK and follow the plasma in a cool loop moving from one footpoint to the other. We apply single-Gaussian fits to the line core, determine the excess emission in the red and blue wings, and derive the red-blue line asymmetry. Results. The blue wing excess at one footpoint shows injection of plasma into the loop that is then flowing to the other side. At the same footpoint, redshifts of the line core indicate that energy is deposited at around 0.1 MK. The enhanced pressure would then push down the cool plasma and inject some plasma into the loop. In the middle part of the loop, the spectral tilts of the line profiles indicate the presence of a helical structure of the magnetic field, and the line wings are symmetrically enhanced. This is an indication that the loop is driven through the injection of helicity at the loop feet. Conclusions. Iftheloopisdriventobehelical,thenonecanexpectthatthemagneticfieldwill be in a turbulent state, as it has been shown by existing MHD models. The turbulent motions could provide an explanation of the (symmetric) line wing enhancements which have been seen also in loops at coronal temperatures, but have not been understood so far.Comment: 26 pages, 11 figures, Accepted for publication in A&

Heating and cooling of coronal loops observed by SDO

Context: One of the most prominent processes suggested to heat the corona to well above 10^6 K builds on nanoflares, short bursts of energy dissipation. Aims: We compare observations to model predictions to test the validity of the nanoflare process. Methods: Using extreme UV data from AIA/SDO and HMI/SDO line-of-sight magnetograms we study the spatial and temporal evolution of a set of loops in active region AR 11850. Results: We find a transient brightening of loops in emission from Fe xviii forming at about 7.2 MK while at the same time these loops dim in emission from lower temperatures. This points to a fast heating of the loop that goes along with evaporation of material that we observe as apparent upward motions in the image sequence. After this initial phases lasting for some 10 min, the loops brighten in a sequence of AIA channels showing cooler and cooler plasma, indicating the cooling of the loops over a time scale of about one hour. A comparison to the predictions from a 1D loop model shows that this observation supports the nanoflare process in (almost) all aspects. In addition, our observations show that the loops get broader while getting brighter, which cannot be understood in a 1D model.Comment: 9 pages, 7 figures, accepted by A&

Social Media in Dynamic Learning: Logistics and Influential Factors

Educators have been using social media to enrich learning activities and promote interactive and collaborative learning. Under the context of dynamic learning – the way that 21st century’s learners learn, the new challenges are: how educators design such a setting to effectively integrate certain social media tools to improve learning, and what the influential factors might be that educators need to focus during the design. In this article, we employ the concept “logistics” to explain and redefine dynamic design, dynamic learning, and dynamic thinking, which furthermore formulate the framework of the study. This article presents a critical content review of current literature, and an analysis of 276 cases located from the literature on seven factors (Information Logistics, Technology Logistics, Overall Design Logistics, Collaborative Learning, Active Stimulation, Motivation, and Objective-Driven Activities) regarding their influence on the success of social medial supported learning experiences. All seven factors were found to be significant and included in a static predictive model. An in-depth comprehension of this static predictive model is provided, based on which a new dynamic model is proposed

Methods to Analyze Likert-Type Data in Educational Technology Research

Likert-type items are commonly used in education and related fields to measure attitudes and opinions. Yet there is no consensus on how to analyze data collected from these items. In this paper, we first synthesized literature on strategies for analyzing Likert-type data and provided computing tools for these strategies. Secondly, to examine the use and analysis of Likert-type data in the field of educational technology, we reviewed 424 articles that were published in the journal Educational Technology Research and Development between 2016 and 2020. Our review showed that about 50% of the articles reported Likert-type data. A total of 139 articles used Likert-type data as a dependent variable, among which 86% employed parametric methods to analyze the data. In addition, less than 1% of the 139 articles used an ordered probit/ logit model, transformation, or strategy for rescaling Likert-type data to interval data to perform statistical analysis. Finally, to empower educational technology researchers to handle Likert-type data effectively, we concluded the paper with our suggestions and insight regarding alternative strategies and methods

Conducting Synchronous Assessment through Web Videoconference to Improve Online Learning: Case Outcomes with Nonparametric Analysis

Online assessment has always been a challenge to online teaching. Educators have been exploring a variety of methods to perform online assessment. However, it appears that there is not enough work in the field focusing on online synchronous assessment. This paper presents two cases that demonstrate the design and implementation of using web videoconference for synchronous assessment in an educational research methods online course and an instructional video production online course. The purpose of the two cases was to explore whether or with what methods student online learning could be improved through synchronous assessment. Case outcomes were analyzed with nonparametric methods, and the results did show students’ improvement in their learning, specifically in their understanding and mastering of factual, conceptual, procedural and metacognitive knowledge. Methods, procedures, tips and cautions of conducting such videoconference-based synchronous assessment in online courses are discussed