Search for: All records

Solar eclipses present a rare glimpse into the impact of ionospheric electrodynamics on the magnetosphere independent of other well studied seasonal influences. Despite decades of study, we still do not have a complete description of the conditions for geomagnetic substorm onset. We present herein a mutual information based study of previously published substorm onsets and the past two decades of eclipses which indicates the likelihood of co‐occurrence is greater than random chance. A plausible interpretation for this relation suggests that the abrupt fluctuations in ionospheric conductivity during an eclipse may influence the magnetospheric preconditions of substorm initiation. While the mechanism remains unclear, this study presents strong evidence of a link between substorm onset and solar eclipses.

 

Manipulating an articulated object requires perceiving its kinematic hierarchy: its parts, how each can move, and how those motions are coupled. Previous work has explored perception for kinematics, but none infers a complete kinematic hierarchy on never-before-seen object instances, without relying on a schema or template. We present a novel perception system that achieves this goal. Our system infers the moving parts of an object and the kinematic couplings that relate them. To infer parts, it uses a point cloud instance segmentation neural network and to infer kinematic hierarchies, it uses a graph neural network to predict the existence, direction, and type of edges (i.e. joints) that relate the inferred parts. We train these networks using simulated scans of synthetic 3D models. We evaluate our system on simulated scans of 3D objects, and we demonstrate a proof-of-concept use of our system to drive real-world robotic manipulation. 

On 04 December 2021, a total solar eclipse occurred over west Antarctica. Nearly an hour beforehand, a geomagnetic substorm onset was observed in the northern hemisphere. Eclipses are suggested to influence magnetosphere‐ionosphere (MI) coupling dynamics by altering the conductivity structure of the ionosphere by reducing photoionization. This sudden and dramatic change in conductivity is not only likely to alter global MI coupling, but it may also introduce a variety of localized instabilities that appear in both hemispheres. Global navigation satellite system (GNSS) based observations of the total electron content (TEC) in the southern high latitude ionosphere during the December 2021 eclipse show signs of wave activity coincident with the eclipse peak totality. Ground magnetic observations in the same region show similar activity, and our analysis suggest that these observations are due to an “eclipse effect” rather than the prior substorm. We present the first multi‐point interhemispheric study of a total south polar eclipse with local TEC observational context in support of this conclusion.

 

The COVID-19 pandemic forced many colleges and universities to remain on a completely online or remote educational learning for more than a year; however, due to distraction, lack of motivation or engagement, and other internal/external pandemic contributing factors, learners could not pay attention 100% to the learning process. Additionally, given that transportation classes are very hands-on, students could not do the experiment from home due to limited resources available, thereby hampering all three phases of learner interactions. The limitation of the implementation of physical, hands-on laboratory exercises during the pandemic further exacerbated students’ actualization of the critical Accreditation Board for Engineering and Technology (ABET) outcomes in transportation: An ability to develop and conduct experiments or test hypotheses, analyze and interpret data and use scientific judgment to draw conclusions. Subsequently, this paper highlights the development and implementation of experiment centric pedagogy (ECP) home-based active learning experiments in three transportation courses: Introduction to Transportation Systems, Traffic Engineering, and Highway Engineering during the pandemic. Quantitative and qualitative student success key constructs data was collected in conjunction with the execution of classroom observation protocols that measure active learning in these transportation courses. The results reveal a significant difference between the pre, and post- tests of key constructs associated with student success, such as motivation, critical thinking, curiosity, collaboration, and metacognition. The results of the Classroom Observation Protocol for Undergraduate STEM (COPUS) show more active student engagement when ECP is implemented. 

We describe the use of a coplanar waveguide (CPW) whose slots are filled with a resistive film, a resistively loaded CPW (RLCPW), to measure two-dimensional electron systems (2DESs). The RLCPW applied to the sample hosting the 2DES provides a uniform metallic surface serving as a gate to control the areal charge density of the 2DES. As a demonstration of this technique, we present measurements on a Si metal–oxide–semiconductor field-effect transistor and a model that successfully converts microwave transmission coefficients into conductivity of a nearby 2DES capacitively coupled to the RLCPW. We also describe the process of fabricating the highly resistive metal film required for fabrication of the RLCPW.

 

We must be able to predict and mitigate against geomagnetically induced current (GIC) effects to minimize socio‐economic impacts. This study employs the space weather modeling framework (SWMF) to model the geomagnetic response over Fennoscandia to the September 7–8, 2017 event. Of key importance to this study is the effects of spatial resolution in terms of regional forecasts and improved GIC modeling results. Therefore, we ran the model at comparatively low, medium, and high spatial resolutions. The virtual magnetometers from each model run are compared with observations from the IMAGE magnetometer network across various latitudes and over regional‐scales. The virtual magnetometer data from the SWMF are coupled with a local ground conductivity model which is used to calculate the geoelectric field and estimate GICs in a Finnish natural gas pipeline. This investigation has lead to several important results in which higher resolution yielded: (1) more realistic amplitudes and timings of GICs, (2) higher amplitude geomagnetic disturbances across latitudes, and (3) increased regional variations in terms of differences between stations. Despite this, substorms remain a significant challenge to surface magnetic field prediction from global magnetohydrodynamic modeling. For example, in the presence of multiple large substorms, the associated large‐amplitude depressions were not captured, which caused the largest model‐data deviations. The results from this work are of key importance to both modelers and space weather operators. Particularly when the goal is to obtain improved regional forecasts of geomagnetic disturbances and/or more realistic estimates of the geoelectric field.

 

We show that a white‐light all‐sky imager can estimate Pedersen conductance with an uncertainty of 3 mho or 40%. Using a series of case studies over a wide range of geomagnetic activity, we compare estimates of Pedersen conductance from the backscatter spectrum of the Poker Flat Incoherent Scatter Radar with auroral intensities. We limit this comparison to an area bounding the radar measurements and within a limited area close to (but off) imager zenith. We confirm a linear relationship between conductance and the square root of auroral intensity predicted from a simple theoretical approximation. Hence, we extend a previous empirical result found for green‐line emissions to the case of white‐light off‐zenith emissions. The difference between the radar conductance and the best‐fit relationship has a mean of −0.76 ± 4.8 mho and a relative mean difference of 21% ± 78%. The uncertainties are reduced to −0.72 ± 3.3 mho and 0% ± 40% by averaging conductance over 10 min, which we attribute to the time that auroral features take to move across the imager field being greater than the 1‐min resolution of the radar data. Our results demonstrate and calibrate the use of Time History of Events and Macroscale Interactions during Substorms all‐sky imagers for estimating Pedersen conductance. This technique allows the extension of estimates of Pedersen conductance from Incoherent Scatter Radars to derive continental‐scale estimates on scales of ~1–10 min and ~100 km². It thus complements estimates from low‐altitude satellites, satellite auroral imagers, and ground‐based magnetometers.

 

Substorms are a highly variable process, which can occur as an isolated event or as part of a sequence of multiple substorms (compound substorms). In this study we identify how the low‐energy population of the ring current and subsequent energization varies for isolated substorms compared to the first substorm of a compound event. Using observations of H⁺and O⁺ions (1 eV to 50 keV) from the Helium Oxygen Proton Electron instrument onboard Van Allen Probe A, we determine the energy content of the ring current in L‐MLT space. We observe that the ring current energy content is significantly enhanced during compound substorms as compared to isolated substorms by ∼20–30%. Furthermore, we observe a significantly larger magnitude of energization (by ∼40–50%) following the onset of compound substorms relative to isolated substorms. Analysis suggests that the differences predominantly arise due to a sustained enhancement in dayside driving associated with compound substorms compared to isolated substorms. The strong solar wind driving prior to onset results in important differences in the time history of the magnetosphere, generating significantly different ring current conditions and responses to substorms. The observations reveal information about the substorm injected population and the transport of the plasma in the inner magnetosphere.