Electron density measurements from the Floating Potential Measurement Unit (FPMU) onboard the International Space Station allow us to observe the structure of the equatorial ionosphere. During two geomagnetically quiet time periods, we examined the equatorial F‐region structure at night using FPMU electron density measurements along with Swarm spacecraft electron density measurements and Total Electron Content from ground‐based Global Navigation Satellite System receivers for comparison. During these time periods, the equatorial ionization anomaly (EIA) extended to local times late as post‐midnight in some cases. The EIA occurrences at night showed a longitudinal dependence. The mean density of the EIA peaks exhibited a 3‐wave pattern in longitude likely due to lower atmospheric planetary wave activity, similar to the longitudinal dependence previously observed in the EIA.
We present a concept for a high-precision optical atomic clock (OAC) operating on an Earth-orbiting space station. This pathfinder science mission will compare the space-based OAC with one or more ultra-stable terrestrial OACs to search for space-time-dependent signatures of dark scalar fields that manifest as anomalies in the relative frequencies of station-based and ground-based clocks. This opens the possibility of probing models of new physics that are inaccessible to purely ground-based OAC experiments where a dark scalar field may potentially be strongly screened near Earth’s surface. This unique enhancement of sensitivity to potential dark matter candidates harnesses the potential of space-based OACs.
more » « less- Award ID(s):
- 2143870
- NSF-PAR ID:
- 10380932
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Quantum Science and Technology
- Volume:
- 8
- Issue:
- 1
- ISSN:
- 2058-9565
- Page Range / eLocation ID:
- Article No. 014003
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract Accurate measurements of global lightning are essential for understanding present and future atmospheric electricity, composition, and climate. The latest space‐based lightning detector, the Geostationary Lightning Mapper (GLM), was the first to be placed in geostationary orbit, with a continuous view of most of the American continents. Prior to the GLM, the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) satellite collected lightning measurements from which numerous lightning climatologies have been developed, including those used in global models. However, this study finds that both the GLM and a second, similar LIS placed on the International Space Station (ISS) in 2017 detect lightning at similar rates and are undercounting lightning compared to ground‐based Lightning Mapping Arrays (LMAs). The GLM undercounts lightning by an average factor of 7.0, reaching a maximum over 120 as a function of satellite zenith angle, radar reflectivity at a height where the temperature is −10°C, flash height, and thunderstorm polarity. The LIS is estimated to undercount lightning by an average factor of 5.6, reaching a maximum of 75.0 as a function of radar reflectivity at the −10°C level, flash height, and thunderstorm polarity. Preliminary predictive equations for the GLM and LIS lightning undercount factor, or scaling factor (SF), use ice‐water content, equilibrium level, flash height, and satellite zenith angle, all of which can be derived in models. These equations are developed to encourage updating lightning parameterizations within global models and will likely increase modeled lightning's effects on atmospheric electrical circuits, composition, chemistry, and climate change.
-
Abstract Vera C. Rubin Observatory is a ground-based astronomical facility under construction, a joint project of the National Science Foundation and the U.S. Department of Energy, designed to conduct a multipurpose 10 yr optical survey of the Southern Hemisphere sky: the Legacy Survey of Space and Time. Significant flexibility in survey strategy remains within the constraints imposed by the core science goals of probing dark energy and dark matter, cataloging the solar system, exploring the transient optical sky, and mapping the Milky Way. The survey’s massive data throughput will be transformational for many other astrophysics domains and Rubin’s data access policy sets the stage for a huge community of potential users. To ensure that the survey science potential is maximized while serving as broad a community as possible, Rubin Observatory has involved the scientific community at large in the process of setting and refining the details of the observing strategy. The motivation, history, and decision-making process of this strategy optimization are detailed in this paper, giving context to the science-driven proposals and recommendations for the survey strategy included in this Focus Issue.more » « less
-
more » « less
Abstract Fluid interfaces significantly influence the dynamics of protein solutions, effects that can be isolated by performing experiments in microgravity, greatly reducing the amount of solid boundaries present, allowing air-liquid interfaces to become dominant. This investigation examined the effects of protein concentration on interfacial shear-induced fibrillization of insulin in microgravity within a containerless biochemical reactor, the ring-sheared drop (RSD), aboard the international space station (ISS). Human insulin was used as a model amyloidogenic protein for studying protein kinetics with applications to in situ pharmaceutical production, tissue engineering, and diseases such as Alzheimer’s, Parkinson’s, infectious prions, and type 2 diabetes. Experiments investigated three main stages of amyloidogenesis: nucleation studied by seeding native solutions with fibril aggregates, fibrillization quantified using intrinsic fibrillization rate after fitting measured solution intensity to a sigmoidal function, and gelation observed by detection of solidification fronts. Results demonstrated that in surface-dominated amyloidogenic protein solutions: seeding with fibrils induces fibrillization of native protein, intrinsic fibrillization rate is independent of concentration, and that there is a minimum fibril concentration for gelation with gelation rate and rapidity of onset increasing monotonically with increasing protein concentration. These findings matched well with results of previous studies within ground-based analogs.
-
more » « less
Abstract. A comparison of polar stratospheric cloud (PSC) occurrence from 2006 to2010 is presented, as observed from the ground-based lidar station at McMurdo(Antarctica) and by the satellite-borne CALIOP lidar (Cloud-Aerosol Lidarwith Orthogonal Polarization) measuring over McMurdo. McMurdo (Antarctica) isone of the primary lidar stations for aerosol measurements of the NDACC (Network forDetection of Atmospheric Climate Change). The ground-based observations havebeen classified with an algorithm derived from the recent v2 detection andclassification scheme, used to classify PSCs observed by CALIOP.
A statistical approach has been used to compare ground-based and satellite-based observations, since point-to-point comparison is often troublesome dueto the intrinsic differences in the observation geometries and the imperfectoverlap of the observed areas.
A comparison of space-borne lidar observations and a selection of simulationsobtained from chemistry–climate models (CCMs) has been made by using a series ofquantitative diagnostics based on the statistical occurrence of different PSCtypes. The distribution of PSCs over Antarctica, calculated by severalCCMVal-2 and CCMI chemistry–climate models has been compared with the PSCcoverage observed by the satellite-borne CALIOP lidar. The use of severaldiagnostic tools, including the temperature dependence of the PSCoccurrences, evidences the merits and flaws of the different models. Thediagnostic methods have been defined to overcome (at least partially) thepossible differences due to the resolution of the models and to identifydifferences due to microphysics (e.g., the dependence of PSC occurrence onT−TNAT).
A significant temperature bias of most models has been observed, as well as alimited ability to reproduce the longitudinal variations in PSC occurrencesobserved by CALIOP. In particular, a strong temperature bias has been observedin CCMVal-2 models with a strong impact on PSC formation. The WACCM-CCMI(Whole Atmosphere Community Climate Model – Chemistry-Climate ModelInitiative) model compares rather well with the CALIOP observations, althougha temperature bias is still present.
