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  1. Abstract Background The Learning Assistant (LA) model with its subsequent support and training has evidenced significant gains for undergraduate STEM learning and persistence, especially in high-stakes courses like Calculus. Yet, when a swift and unexpected transition occurs from face-to-face to online, remote learning of the LA environment, it is unknown how LAs are able to maintain their motivation (competence, autonomy, and relatedness), adapt to these new challenges, and sustain their student-centered efforts. This study used Self-Determination Theory (SDT) to model theoretical aspects of LAs’ motivations (persistence and performance) both before and after changes were made in delivery of a Calculus II course at Texas Tech University due to COVID-19 interruptions. Results Analysis of weekly written reflections, a focus group session, and a post-course questionnaire of 13 Calculus II LAs throughout Spring semester of 2020 showed that LAs’ reports of competence proportionally decreased when they transitioned online, which was followed by a moderate proportional increase in reports of autonomy (actions they took to adapt to distance instruction) and a dramatic proportional increase in reports of relatedness (to build structures for maintaining communication and building community with undergraduate students). Conclusions Relatedness emerged as the most salient factor from SDT to maintain LA self-determination due to the COVID-19 facilitated interruption to course delivery in a high-stakes undergraduate STEM course. Given that online learning continues during the pandemic and is likely to continue after, this research provides an understanding to how LAs responded to this event and the mounting importance of relatedness when LAs are working with undergraduate STEM learners. Programmatic recommendations are given for enhancing LA preparation including selecting LAs for autonomy and relatedness factors (in addition to competence), modeling mentoring for remote learners, and coaching in best practices for online instruction. 
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  2. In this study, we analyze 44 terrestrial gamma-ray flashes (TGFs) detected by the Fermi Gamma-ray Burst Monitor (GBM) occurring in 2014–2016 in conjunction with data from the U.S. National Lightning Detection Network (NLDN). We examine the characteristics of magnetic field waveforms measured by NLDN sensors for 61 pulses that occurred within 5 ms of the start-time of the TGF photon flux. For 21 (out of 44) TGFs, the associated NLDN pulse occurred almost simultaneously with (that is, within 200 μs of) the TGF. One TGF had two NLDN pulses within 200 μs. The median absolute time interval between the beginning of these near-simultaneous pulses and the TGF flux start-time is 50 μs. We speculate that these RF pulses are signatures of either TGF-associated relativistic electron avalanches or currents traveling in conducting paths “preconditioned” by TGF-associated electron beams. Compared to pulses that were not simultaneous with TGFs (but within 5 ms of one), simultaneous pulses had higher median absolute peak current (26 kA versus 11 kA), longer median threshold-to-peak rise time (14 μs versus 2.8 μs), and longer median peak-to-zero time (15 μs versus 5.5 μs). A majority (77%) of our simultaneous RF pulses had NLDN-estimated peak currents less than 50 kA indicating that TGF emissions can be associated with moderate-peak-amplitude processes. The lightning flash associated with one of the TGFs in our data set was observed by a Lightning Mapping Array, which reported a relatively high-power source at an altitude of 25 km occurring 101 μs after the GBM-reported TGF discovery-bin start-time. 
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  3. Abstract

    We report on three classes of terrestrial gamma ray flashes (TGFs) from the (RHESSI) satellite. The first class drives the detectors into paralysis, being observed usually through a few counts on the rising edge and the later tail of Comptonized photons. These events—and any bright TGF—reveal their true luminosity more clearly via their Compton tail than via the main peak, since the former is unaffected by the unknown beaming pattern of the unscattered radiation, and Comptonization mostly isotropizes the flux. This technique could be applied to TGFs from any mission. The second class is more than usually bright and long in duration. When the magnetic field at the conjugate point is stronger than at the nearby footpoint, we find that 4 out of 11 such events show a significant signal at the time expected for a relativistic electron beam to make a round trip to the opposite footpoint and back. We conclude that a large fraction of TGFs lasting more than a few hundred microseconds may include counts due to the upward moving secondary particle beam ejected from the atmosphere. Finally, using a new search algorithm to find short TGFs in RHESSI, we see that these tend to occur more often over the oceans than land, relative to longer‐duration events. In the feedback model of TGF production, this suggests a higher thunderstorm potential, since more feedback per avalanche implies fewer “generations” of avalanches needed to complete the TGF discharge.

     
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  4. Abstract

    On February 8, 2019, the Atmosphere‐Space Interaction Monitor observed a terrestrial gamma‐ray flash (TGF) and an Elve from a positive intracloud (+IC) lightning during the initial breakdown stage of a lightning flash north east of Puerto Rico. A second Elve produced by the return stroke (RS) of a negative cloud‐to‐ground (−CG) lightning was observed 456 ms later about 300 km south of the first one. Radio measurements show that a short (30 μs) and large (280 kA km) energetic in‐cloud pulse (EIP) produced the electromagnetic (EM) wave for the first Elve while the RS of the −CG was the EM source for the second Elve. Assuming that the EIP and the RS were the sources of the 777 nm emissions, both the delay relative to the ultra‐violet pulse and the shape and duration of the 777 nm emissions can be explained by scattering and absorption inside the clouds. The TGF produced by the +IC lightning had the same duration as the EIP (∼30 μs). Due to the ±80 μs timing uncertainty of the TGF, we can only state that TGF was produced just before or most likely simultaneously with the EIP. The large 777 nm pulse indicates that a large part of the EIP was produced by a current flowing in a hot channel, but it is likely that the TGF current also contributed significantly to the EIP.

     
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  5. Abstract

    We present an event that was detected byFermiGamma‐ray Burst Monitor on 4 February 2014 as the spacecraft was flying over Madagascar. We interpret the three pulses during this event (herein known as 140204581) as the following: the first pulse as a terrestrial gamma‐ray flash, the second as a 2 ms long terrestrial electron beam (TEB) 0.5 ms after the terrestrial gamma‐ray flash, and the last pulse as the TEB mirror pulse 90 ms after the TEB. The nature of these events were confirmed using both the World Wide Lightning Location Network and the Earth Networks Total Lightning Network, which detected the same simultaneous sferic underneath the spacecraft and in the magnetic footprint. Several models were fit to the data, and results show that the vertical narrow beam model was found to be inconsistent with the data.

     
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