The increasing ubiquity of high-resolution imagery has yielded many observations of water-filled crevasses across the surfaces of glaciers and ice sheets (e.g., Figure 1a). The subsurface character of these features, however, is not apparent in imagery, nor can it be fully elucidated even through field geophysics. Thus, what visible surface water in crevasses indicates about englacial hydrology, including whether there is a surface-to-bed connection, is currently subjective and interpreted differently by different scientists. Application of a physically based crevasse model to this problem shows that if a crevasse visibly holds water, it likely does not connect to the bed. The crevasse model incorporates depth-dependent visco-elastic deformation and refreezing to evolve the size and shape of a water-filled crevasse over hourly to decadal timescales (Figure 1b). Seasonally, visco-elastic closure tends to form a neck at the water line of most crevasses. Over a year or more, this neck can pinch off, isolating a pod of water that can extend hundreds of meters beneath the surface. The area above the neck persists as a 1–5 meter wide, 10–40 meter deep “ditch”: the surface expression of a dead crevasse that no longer receives surface melt. Accumulation of meltwater in these ditches is consistent with observations; the model results show that the ditches are not hydrologically connected to the crevasse or to the bed. These findings are consistent with recent observational work by Chudley et al. (2020), who concluded that visible water in crevasses sited in compressive stress settings was not connected to the bed. Observations of sudden drainage of these ditches show that reconnection to the englacial system, and potentially the bed, must be possible. The smooth bathymetry of the ditches, however, discourages formation of the starter crack needed to reactivate these hydrofractures. Thus, an external forcing, such as advection into a more-extensional stress setting, may be required to drain them. Overall, model results suggest that these water-filled ditches are shallow (<40 meters), overlie an englacial pod of liquid water that is in the process of refreezing, and are not connected to the bed.

Lithospheric yield stress is a key parameter in controlling tectonic processes. We calculate yield stress for a range of conditions appropriate to the Archean Earth, including hotter mantle potential temperatures and a range of Moho temperatures using 2D high resolution numerical geodynamic modelling techniques. This range of conditions are evaluated for generating felsic, tonalite-trondhjemite-granodiorite (TTG), crust with the results bench marked against the preserved rock record. The model results indicate that lithospheric yield stress slightly lower than the present-day Earth values (i.e. < 100 MPa) generates TTG melt volumes similar to those preserved in the rock record. In particular, large volumes of TTG melts form in the tails of lithospheric drips. Melting occurs profusely within the thinner portions of the drips as these regions are more ef�ciently heated by the enclosing hotter mantle. In contrast, only limited melting occurs in regions of thickened crust, in part because the weaker lithosphere cannot sustain crustal thickening for long time periods, resulting in its removal through drips. Our models highlight the dominance of non-plate tectonic mechanisms in producing TTGs under the conditions that operated on the hotter Archean Earth.

The scale and extent of the effects of COVID-19 on our lives is unmatched by any other recent natural disaster. Effective management of the spread and consequences of this pandemic can reduce the burden on health and help in managing the different costs by relaxing restrictions. Understanding this need, our interdisciplinary team of geo and health scientists at the University of Nebraska Medical Center (UNMC) developed a multi-layered interactive dashboard in March 2020. The dashboard provides an automatically updating map of COVID case numbers and their time series in Nebraska counties. Also, Nebraska’s pandemic response leaders can see each hospital and its number of beds and contact information, the location of dialysis centers, long term care facilities, and pharmacies; the name of the emergency response coordinator; and the number of electricity-dependent Medicare beneficiaries in each county. The UNMC Dashboard, has helped the emergency response and health departments of Nebraska. It has received attention from local to international level. In addition to garnering public recognition, the Dashboard established connections between our team and stakeholders in our original climate tracking projects, as well as with other groups with whom we had not previously collaborated. We have established a close connection with Nebraska Medicine, one of the top medical facilities in the region, and their demand forecasting team. Also, we have developed new connections with out of state contacts in health department, resulting into an expanded version of the dashboard. Additionally, the dashboard demonstrated our capabilities and strengthened our relationships with local health departments in Nebraska. One of our primary projects relates to public health emergency preparedness for extreme weather and climate events in Nebraska. The success of that project depends on collaboration with different health officials in the state, who are now more aware of our team and our capability to provide practical solutions and tools. We suggest that this system can adapt to different frameworks, such as the Emergency Risk Framework (ERF) by World Health Organization (WHO). Our system provides the foundation for the information sharing required by such systems -therefore helping with communication and decision making.

One possible human response to climate change and other environmental stresses is migration. However, migration is complex, multi-causal phenomenon, and the complexity of human migration poses a challenge for researchers who aim to study the effects of environmental changes on population mobility. This project aims to understand how changing environmental conditions and livelihood opportunities impact migration decisions in coastal Bangladesh. We are developing an original agent-based model (ABM) that combines stylized environmental change dynamics with livelihood to understand how these dynamics impact migration decisions as well as what feedbacks may exist between them. The ABM uses agents to represent households, which consist of individuals, within a single origin community. At each step of the model, the household assesses the expected utility of different livelihood options within the community for each of its members, including agricultural work on the household’s land (if any), seeking paid employment within the community, and pursuing non-agricultural livelihood activities. After assessing opportunities within the community, households will decide whether or not a household member should seek opportunities outside the community. The model imposes stochastic droughts that impact crop yields. We report preliminary results from this model, comparing simulated migration patterns to empirical observations. Future work will incorporate more complex and psychologically realistic decision-making heuristics, as well as diverse destination locations and the possibility of return migration.

ICESat-2, the first photon counting satellite, maps the earth’s surface with unprecedented details and accuracy. However, the resulting photon clouds, distributed as the ATL-03 geocoded photon product, are vast, unstructured, and noisy datasets. The high density and four-dimensional nature of the photon dataset (location and time), coupled with different responses over different surfaces (e.g., ice, forest cover, water), pose a unique and challenging problem regarding surface detection’s overall objective of intelligently reducing the data volume. Multiscale models uncover hidden structures in data due to their ability to analyze the underlying processes at multiple scales. Besides the traditional wisdom of using multiple scales for improving local and global approximations, in this work, we show their application as an intelligent sampling mechanism for redundant and noisy datasets. Our proposed approach’s fundamental idea is the generation of data dependent and multiscale basis functions and corresponding representative sparse representations, which retain points essential for minimizing the error of reconstruction. Thereby, points associated with rapid spatial change are chosen, while those that are easily reconstructed using the smooth basis functions are discarded. As the final output, the algorithm provides an efficient sparse representation of the data that captures all relevant features for modeling and prediction with quantified uncertainty. Our presentation includes a detailed description of the algorithm and theory as applied to process the ATL-03 geolocated photon product of the ICESat-2 mission. We will demonstrate the efficiency of our approach by examples of different ice sheet surfaces, including heavily crevassed glaciers, that pose a challenge for currently used change detection methods.

The Adler Planetarium’s Teen Programs engages hundreds of young people in authentic STEM experiences each year. Several of our programs focus on artificial light at night (ALAN), a critical environmental, health, ecological and astronomical issue. Our work in ALAN Community Advocacy and Education began in 2015 through Youth Organization for Lights Out (YOLO), a bilingual program in English and Spanish based in Chicago’s predominantly Mexican and Mexican-American Little Village neighborhood. YOLO program participants use tools to collect and analyze light pollution data, attend field trips to local and state dark sky sites, facilitate telescope viewing at the Adler and in their community, and develop prototype solutions and action plans to increase awareness of light pollution’s local effects in Chicago. Programs focused on Instrumentation and Research grew out of the Adler’s educational high-altitude ballooning program, Far Horizons. In 2018, Far Horizons astronomers and engineers began developing Mission NITELite (Night Imaging of Terrestrial Environments), a high altitude balloon-based light pollution mapping mission along with undergraduate interns. To complement NITELite, Far Horizons designed GONet (Ground Observing Network), a low-cost all-sky imaging system to measure sky quality at night as part of its Stratonauts teen program. In 2019, high school students helped design, test, and build 50 GONet units as a potential new standard for worldwide ALAN monitoring. In 2020, Adler teen interns are working with the Cook County Forest Preserves to quantify regional sky quality with GONets in support of an application for an Urban Night Sky Place designation from the International Dark-Sky Association. Reflecting the collaborative nature of science, teens in the Instrumentation and Research programs partner closely with peers in the Community Advocacy and Education programs, learning from one another’s perspective while undertaking joint projects.

Simple neutral particle detectors consisting of organic scintillators, sensitive photodetectors, and readout systems have been used to great effect in space- and Earth-based science for observing gamma rays and particle radiation from solar weather, astrophysical phenomena, and even lightning storms on Earth. The calibration of simple gamma ray detectors was improved through kernel density estimation (KDE) in a user-friendly Jupyter notebook running a Python script. When calibrating organic particle detectors, a gamma ray source is applied and the distribution of raw voltages produced by the detector are represented in a histogram including a distinct Compton edge. The location of the edge in the histogram can be associated with the energy of the gamma ray source to convert the histogram of voltage measurements into a representation of the gamma ray energies interacting with the detector. The process of estimating the location of the edge on a histogram of real measurements with imperfect resolution is often done by hand or with a half gaussian fit, but we propose an alternative technique where KDE of the raw voltages replaces the histogram. Using KDE, Gaussian kernels are built up to a representation of the underlying energy distribution which can be easily numerically differentiated. The minimum of the modified distribution identifies the location of the Compton edge, regardless of the resolution of the detector. To demonstrate the technique on a model of a Compton edge, we calculated the theoretical Klein-Nashina Compton distribution of Cesium-137 gamma ray interactions, created a model of the edge with a piecewise 2nd order polynomial, and convolved the piecewise function with a Gaussian to approximate the experimental response. The response was numerically differentiated and the location of the minimum was consistent with the energy of the Compton edge, as the inflection point of the approximated Gaussian distribution occurs at the Compton edge. We also demonstrate the technique with data from a MEGAlib simulation of a simple block particle detector. For projects with repeated adjustment and testing of particle detectors, this method should improve consistency and accuracy of calibration while reducing analysis time.

The Bransfield Strait is a semi enclosed region located between the Antarctic Peninsula and the South Shetland Islands (SSI), where the Bransfield Current (BC) is a relatively warm baroclinic jet (0-250 m) flowing northeastward along the southern slope of the SSI. Recent studies have shown that the BC propagates as a buoyant gravity current, recirculating around the north-eastern tip of the islands while shedding an anticyclonic eddy. However, most previous works are based on summertime measurements and a more comprehensive spatio-temporal view of the regional circulation is still lacking. In this study we provide the first seasonal description of the BC based on an extensive dataset of direct velocity measurements. These measurements were routinely collected along ship tracks from 275 cruises between 1999 and 2014. Seasonally, the horizontal structure of the BC flowing as a coastal jet appears more prominent during spring and summer, when its pathway extends along the island slopes over 180 km at velocities up to 45 cm/s, from Deception Island towards King George Island. During these seasons, the BC is consistently narrower at the beginning of its path (15-20 km wide), and wider before starting its recirculation around the SSI (30 km wide). Through autumn, this pattern is also apparent but less intense, especially south off Livingston-Robert Islands, where subsurface velocities (150 m) are lower at about 10-15 cm/s. The scarcity of winter data confirms the existence of a relatively strong coastal jet with mean velocities about 34 cm/s at least south off Nelson Island. Vertically, the BC also displays a distinctive pattern. At the wake of the islands, the core of the current flows hugging the island slopes with velocities about 35 cm/s at 150 m. Differently, when located at channels between islands, the core of the current migrates offshore flowing at 30-45 cm/s. In terms of zonal volume transport (0-250 m), our estimates indicate that the BC transports about 0.85, 0.93, 0.90 and 1.01 Sv from spring to winter, respectively, at the location where all seasons are covered by data (south off Nelson Island). These results support the BC is a recurrent feature of the circulation in Bransfield Strait, flowing northeastward all along the southern slope of the SSI not only during summer but also during spring and autumn.

The extent to which terrestrial weather below 30 km in altitude can influence the dynamics and mean state of the thermosphere (ca., 100-500 km) is a fascinating discovery of the last two decades or so. Waves that are excited by deep convection in the tropical troposphere and propagate vertically into the thermosphere are responsible for much of this influence. Tropospheric convection associated with the Madden JulianOscillation(MJO), the dominant mode of intra-seasonal variability in tropical convection and circulation, has been known to modulate the intensity of upward propagating gravity waves and Kelvin waves. An MJO impact on tides was already proposed over two decades ago, but only recent gains in satellite observational capabilities allows one to quantify their effect from observations. Previous work by Gasperini et al. [2017a] demonstrate that a 90-day oscillation in tropospheric convection during 2009-2010 is imprinted on both thermospheric mean winds and the eastward propagating wavenumber 3 diurnal (DE3) tidal amplitudes observed by the GOCE and CHAMP satellites and modeled with the TIME-GCM. In a follow-on modeling-based study, Gasperini at al. [2020] present statistical evidence for a strong connection (+/-12%) between the phase of the tropospheric MJO and the amplitudes of the thermospheric DE3 and 3-day ultra-fast Kelvin wave (UFKW), two of the most prominent and well-established waves from the tropical wave spectrum that preferentially propagate into the thermosphere. These recent studies demonstrate that strong coupling between the troposphere and the thermosphere occurs on intra-seasonal timescales, raising important questions that have implications for the whole atmosphere system. In this work, we present evidence for a strong quasi-60 day oscillation in GOLD column-integrated O/N2 and Swarm-C total mass density during 2018-2019. A similar and concurrent oscillation is observed in the DE3 and SE2 tidal amplitudes derived from SD/WACCM-X. Spectral analysis of OLR reveals a similar oscillation in tropical tropospheric convection that is shown to be eastward propagating with s=-1 and is thus consistent with an MJO event.

The Brine Availability Test in Salt (BATS) is a field heater test being conducted in the bedded salt formation at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM. BATS is focused on exploring brine availability as part of a wider investigation into the disposal of heat-generating radioactive waste in salt. Brine has the potential to transport radionuclides, corrode waste forms and packages, reduce criticality, and pressurize porosity to resist closure through salt creep. In BATS, two identical arrays of horizontal boreholes were constructed in an experimental drift, 650 m below ground at WIPP. In each array, 13 observational boreholes were installed around a central borehole. One of the two array was heated, and the other array was left at ambient temperature. During the first heating phase (January to March 2020), the 750 W heater ran for 4 weeks. The central boreholes included dry nitrogen gas circulation behind a packer. The gas stream removed moisture which flowed into the boreholes. The gas stream was analyzed in-drift for stable water isotopes using a cavity ringdown spectrometer and gas composition using a quadrupole mass spectrometer. The satellite boreholes in each array included numerous thermocouples, electrical resistivity tomography (ERT) electrodes, acoustic emissions (AE) piezoelectric transducers, distributed temperature and strain fiber optics, and a cement seal exposure tests (both sorel and fly-ash base concretes). Cores from the boreholes were X-ray CT imaged for mineralogical and fracture distribution. We present an overview of the first phase of the test, and illustrate key data collected during the first heating cycle. Follow-on tests in the same boreholes will include gas and liquid tracer tests and additional packer-based gas permeability testing. New boreholes for the next round of BATS in 2021 are being planned.

Peatlands are becoming recognized as important carbon sequestration centers where, through restoration projects, peatlands may stop being considered as carbon sources and become carbon neutral or possibly carbon negative. Restoration projects require a knowledge of intra-peat variation across these, sometimes, vast areas. The integration of multidimensional geophysical tools, digital elevation models and satellite remote sensing products combined with modern data analytic techniques may provide a rapid means of accessing variations over broad spatial scale. In this study an airborne radiometric survey, being flown nationally over the Republic of Ireland, is shown to be able to delineate potential management zones within an industrial raised peat bog. Radiometric data is particularly suited to peat studies as they are sensitive to water content. Peat, as a mostly organic material, acts as a low signal environment where variations in the signal are linked to intra-peat variation of either depth or water content. This study uses an unsupervised, self-organizing map clustering methodology to group the radiometric signal into three zones interpreted as 1) the edge of the bog where peat layer is thinning and there is influence on the radiometric signal from non-peat soils outside of the bog, 2) the normal peat conditions where depth and saturation appear as a relative constant in the radiometric response and 3) areas where the peat is either thinner, drier, or potentially somewhat mineralised. The addition of other data layers such as elevation, slope and satellite imagery may help better define these zones and a ground geophysical survey is planned to test the results of this study. The definition of such potential management zones could aid any restoration project in the initial stages or act as a baseline study to monitor changes to the peatland during and after a restoration project is complete.

Being at the interface of the geosphere, the biosphere, and the atmosphere makes the soil a particularly challenging object. Nevertheless, its importance in ecological and environmental domains should encourage researchers to make use of new technologies, like 3D printing, to improve their comprehension of soils. With 3D printing we can build up objects by adding materials layer-by-layer based on a three-dimensional model, producing almost any geometrically complex shape or feature in a wide range of materials. Here we present the major challenges and opportunities of 3D printing for its application into soil science. We show that despite the remarkable achievements in 3D printing development during the past few years, it is still under-used in the field of soil science. Besides the 3D printing technology uses considering the soil as a source of mineral raw materials, or as the basis for the development of technical infrastructure, new researches highlight the functioning of the soil itself as an ecological compartment. Indeed, one of the most important challenges for the application of 3D printing in this area is the accurate modeling and replication of the soil structure and composition. This would require 3D-printed objects to be made of biocompatible yet chemically and mechanically stable materials manufactured under controlled conditions, which can mimic the many interactions occurring at this scale. Having 3D-printed objects with strict and controlled composition and structure could help academics and researchers to conduct reproducible experiments and gain a better understanding of the parameters controlling soil ecology and functioning. This opens a new way to broader utilization of 3D printing in soil science in the near future.

Urban expansion is a global trend primarily determined by overpopulation, particularly in developing countries like India. The pattern and boundary of urban expansion could be observed and modelled on a Spatio-temporal dimension in the Asan watershed, situated in western Doon Valley, Uttarakhand, India. The specific objectives of the present study are: 1) Monitoring Land Use Land Cover (LULC) change detection and its impact on the hydrological regime of the watershed, 2) Generation of urban growth pattern map to identify the urban expansion along with the directions and distance from the watershed centroid. To achieve the objectives, the four LULC maps of different years are generated through Landsat and LISS-IV dataset from 1980 to 2016. The eight classified classes of LULC includes: build-up (urban and rural), cropland, fallow land, plantation, evergreen needle leaf forest, deciduous broadleaf forest, mixed forest, and water bodies. The LULC change analysis concludes that the built-up area continuously expanding at an alarming rate, nearly four folds in the last 36 years. The major areal portion of cropland and plantation are converted into build-up at a faster rate after 1995 whereas the areal extent of water bodies are also reduced. Based on monitoring of urban growth, the wind rose tool revealed that the southwest direction is the dominant direction of the urban expansion till 1980 and 1980-1995 which contribute 48% and 47.61% respectively of the total urban area of the watershed. However, in the period 1995-2008 and 2008-2016, the eastern direction is predominant, which contribute 36.44% and 35.27% respectively from the total urban areal expansion. This reflects a situation where the eastern direction is expected to dominate in the next years. Consequences of urban expansion create pressure on the into the watershed which leads to degradation of natural resources, forest environment and hydrological elements of the watershed.

SIHLA (Spatial/Spectral Imaging of Heliospheric Lyman Alpha pronounced as ‘Scylla’ [e.g. Homer, Odyssey, ~675-725 BCE] investigates fundamental physical processes that determine the interaction of the Sun with the interstellar medium (ISM); the Sun with the Earth; and the Sun with comets and their subsequent evolution. To accomplish these goals, SIHLA studies the shape of the heliosphere and maps the solar wind in 3D; characterizes changes in Earth’s extended upper atmosphere (the hydrogen ‘geocorona’); discovers new comets and tracks the composition changes of new and known ones as they pass near the Sun. SIHLA is a NASA Mission of Opportunity that has just completed its Phase A study (the Concept Study Report or CSR). At the time of the writing of this abstract NASA has not decided whether to fly this small satellite mission or its competitor (GLIDE: PI Prof. Lara Waldrop). SIHLA observes the ion-neutral interactions of hydrogen, the universe’s most abundant element, from the edge of the solar system to the Earth, to understand the fundamental properties that shaped our own home planet Earth and the heliosphere. From its L1 vantage point, well outside the Earth’s obscuring geocoronal hydrogen cloud, SIHLA maps the entire sky using a flight-proven, compact, far ultraviolet (FUV) hyperspectral imager with a Hydrogen Absorption Cell (HAC). The hyperspectral scanning imaging spectrograph (SIS) in combination with the spacecraft roll, creates 4 maps >87% of the sky each day, at essentially monochromatic lines over the entire FUV band (115 to 180nm) at every point in the scan. During half of these daily sky maps, the hydrogen absorption cell (HAC) provides a 0.001nm notch rejection filter for the H Lyman a. Using the HAC, SIHLA builds up the lineshape profile of the H Lyman a emissions over the course of a year. SIHLA’s SIS/HAC combination enables us to image the result of the ion-neutral interactions in the heliosheath, 100 AU away, in the lowest energy, highest density, part of the neutral atom spectrum – H atoms with energies below 10eV. The novel aspects of SIHLA are the scope of the science done within a MoO budget. The SIHLA projected costs were below the $75M cap with a 31.3% reserve for Phase B-D. The re-purposing of a spectrographic that was part of the DMSP SSUSI line (a copy was flown and NASA TIMED/GUVI and as NASA NEAR/NIS). Risk is extremely low in this Class-D mission with all major elements at least at TRL6 at this time. SIHLA has a high potential for discovery. We expect that we will 1) First detection of the hot H atoms produced directly from the ion-neutral interactions at the heliopause; 2) First detection of structures in Interplanetary Medium H emission, 3) First detection of response of the Earth’s extended (out to lunar orbit) geocorona to solar/geomagnetic drivers, 4) New UV-bright comets as they enter the inner solar system. SIHLA is a hyperspectral imager; at every point in the sky SIHLA obtains the entire FUV spectrum.

Tectonic information available from remote seismometers is compromised by uncertainties in epicenter and depth, which often prevent earthquakes being associated with faults observable in morphologic data. Here we show that careful study of regional recordings can achieve reasonable position and, for the larger events, also depth estimates. We illustrate this with swarms totallying 90 earthquakes of 3.6 mb to 5.5 Mw recorded at coastal stations of the Brazilian Seismographic Network, GSN, GEOSCOPE and Cape Verdes. Seismicity occured in 4 swarms, firstly in 2012 with 7 events in the valley floor and eastern wall near the ridge-transform intersection (4.05º-4.2ºN). Next, five events occurred in 2014, with three in the inner floor (4.8º-4.9ºN) and two under the valley wall (4.7º-4.8ºN). A 70-earthquake swarm in 2016 occurred in the 4.4º-4.8ºN valley floor, in both walls and floor, involving slip on different faults. The last 8 events in 2019 were located outside the median valley near a volcanic seamount. We estimated focal depths of the strongest events with Mw > 5.4 using waveform modeling and focal mechanims reported by the Global Centroid-Moment-Tensor Project. Our best estimated hypocenters lie 5-8 km beneath the seafloor, in keeping with maximum depths typically found with OBSs on the MAR. In contrast, deeper events (10 km) have been found in an OBS experiment around an active detachment fault elsewhere. Multibeam sonar data from the area do reveal a detachment fault surface (“megamullion”), but it ends 10-15 km from the median valley floor, suggesting that it is probably inactive. Although our uncertainties still do not allow the event depths to be discriminated from 10 km, our best estimates are more compatible with shallower normal faulting. Over time, repeating this exercise with many such datasets and comparing with morphologic data should help to resolve the incidence of deeper ruptures associated with detachment faults.

Abstract In order to decipher complex subsurface structures, various seismic imaging techniques have been developed. Full Waveform Inversion (FWI) is one of the most sophisticated approaches in the new generation of seismic imaging algorithms for 2D/3D Earth modeling. An effective implementation of FWI requires a good initial model and intensive computations, among other challenges. To address these challenges, we developed a new FWI scheme, where we perform just a few local inversions under the assumption that the layers present only small lateral variations. We then upscale the local inversions to reconstruct 3D media. This approach also includes Source Signature inversion and does not require an initial model. The algorithm is based on the exact analytical solution of the Navier-Lame equation for a visco-elastic multi-layer model. This solution is represented in the form of Fourier-Bessel integrals, and performs forward modeling calculations about 106 – 107 times faster than conventional finite differences (FD) algorithms. It is free from various numerical artifacts inherent to FD methods, and allows modeling of all known types of seismic waves. The solution also indicates numerous unknown waves in various layered systems (some of the waves are practically impossible to reproduce numerically for the thin layers, using the grids, typical for 3D modeling). The comparison of the exact solution with 3D FDTD results shows excellent agreement. Here we applied this approach to stratified media with small lateral variations (the Earth, consisting of the inclined multi-layer structures). The feasibility of the method was analyzed using traces from synthetic seismograms for the Marmousi model, which were simulated by the 3D elastic SW4 code. A few sources with surrounding geophones were chosen. At the first stage we invert the traces from each geophone to the local stratum under the source, deciphering thicknesses, densities and P,S-wave velocities for each layer. At the second stage we identify the layer boundaries’ slopes and reconstruct the full 3D model. For the Marmousi model we obtained an accurate image down to 2.3 km deep, after which lateral variations were excessive. This result demonstrates that a new FWI scheme exploiting separate inversions, can be applied successfully to the reconstruction of 3D media.

The 2020 COVID-19 pandemic provided a unique opportunity to sample atmospheric gases during a period of very low industrial/human activity. Over 1000 Whole Air Samples were collected in over 30 cities and towns across the United States from April through July 2020 as part of the NASA Student Airborne Research Program (SARP). Sample locations leveraged the geographic distribution across the United States of the undergraduate and graduate students, faculty, and NASA personnel associated with the internship program (44 people total). Each person collected approximately 24 air samples in their city/town with the goal of characterizing local emissions with time during the pandemic. Samples were collected in 2-Liter stainless steel evacuated canisters at approximately 2 meters above ground level. The canisters were shipped to the Rowland/Blake Laboratory at the University of California Irvine and analyzed for methane, carbon dioxide, carbon monoxide, non-methane hydrocarbons, and halocarbons using the gas chromatographic system described in Colman et al. (2001) and Barletta et al. (2002). Initial samples collected in April coincided with the peak of stay-at-home/social distancing orders across most of the United States while samples collected later in the spring and early summer reflect the easing of these measures in most locations. Overall trends in emissions with time across the United States during the pandemic (in several large metro areas as well as rural locations) will be discussed.

In the last few years, the relationship between reconnection and turbulence has received significant attention. A surprising recent result is that laminar reconnection has been shown to exhibit a power law spectrum consistent with the Kolmogorov law of turbulence1. However, there still exists an unanswered question: “Is magnetic reconnection fundamentally an energy cascade?”. The energy cascade can be measured directly as a function of spatial scale length using the generalized von-Karman Howarth equation based on the framework of incompressible Hall MHD2. In this study, we apply this technique to 2.5D kinetic particle-in-cell (PIC) simulations of strong turbulence and laminar reconnection, comparing the two to study the flow of energy across spatial scales (lags). Both the turbulence and reconnection simulations show similar behavior, implying that reconnection fundamentally involves an energy cascade. The largest lags are dominated by a steady decrease in energy (second order structure functions) which drives the global system dynamics. At smaller lags, a relatively constant flow (cascade) of energy occurs from large to small scales which can be associated with an MHD inertial range. At still smaller lags, the rate of energy flow decreases considerably, and this energy flux is dominated by Hall physics. In the reconnection simulation, the cascade of energy is strongly correlated with the reconnection rate, with both shutting off at similar times. References: Adhikari et al., Phys. Plasmas 27, 042305 (2020); https://doi.org/10.1063/1.5128376 Hellinger et al., ApJ Letters 857, L19 (2018); http://doi.org/10.3847/2041-8213/aabc06