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&

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

Toward a Unified Explanation for the Three-part Structure of Solar Coronal Mass Ejections

Coronal mass ejections (CMEs) are associated with the eruption of magnetic flux ropes (MFRs), which usually appear as hot channels in active regions and coronal cavities in quiet-Sun regions. CMEs often exhibit the classical three-part structure in the lower corona when imaged with white-light coronagraphs, including the bright front, dark cavity, and bright core. The bright core and dark cavity have been regarded as the erupted prominence and MFR, respectively, for several decades. However, recent studies clearly demonstrated that both the prominence and hot-channel MFR can be observed as the CME core. The current research presents a three-part CME resulted from the eruption of a coronal prominence cavity on 2010 October 7 with observations from two vantage perspectives, i.e., edge-on from the Earth and face-on from the Solar Terrestrial Relations Observatory (STEREO). Our observations illustrates two important results: (1) For the first time, the erupting coronal cavity is recorded as a channel-like structure in the extreme-ultraviolet passband, analogous to the hot-channel morphology, and is dubbed as warm channel; (2) Both the prominence and warm-channel MFR (coronal cavity) in the extreme-ultraviolet passbands evolve into the CME core in the white-light coronagraphs of STEREO-A. The results support that we are walking toward a unified explanation for the three-part structure of CMEs, in which both prominences and MFRs (hot or warm channels) are responsible for the bright core.Comment: 12 pages, 5 figures, accepted by Ap