Results
- Showing results for:
- Reset all filters
Search results
-
Journal articleLiggins FS, Pickering JC, Nave G, et al., 2021,
New Ritz Wavelengths and Transition Probabilities of Parity-forbidden [Mn II] Lines of Astrophysical Interest
, ASTROPHYSICAL JOURNAL, Vol: 907, ISSN: 0004-637X- Cite
- Citations: 2
-
Journal articleMadanian H, Desai M, Schwartz SJ, et al., 2021,
The Dynamics of a High Mach Number Quasi-perpendicular Shock: MMS Observations
, ASTROPHYSICAL JOURNAL, Vol: 908, ISSN: 0004-637X- Author Web Link
- Cite
- Citations: 19
-
Journal articleChoi KTH, Brindley H, 2021,
COVID-19 lockdown air quality change implications for solar energy generation over China
, Environmental Research Letters, Vol: 16, Pages: 1-10, ISSN: 1748-9326We exploit changes in air quality seen during the COVID-19 lockdown over China to show how a cleaner atmosphere has notable co-benefits for solar concentrator photovoltaic energy generation. We use satellite observations and analyses of the atmospheric state to simulate surface broadband and spectrally resolved direct normal irradiance (DNI). Over Wuhan, the first city placed under lockdown, we show how the atmospheric changes not only lead to a 19.8% increase in broadband DNI but also induce a significant blue-shift in the DNI spectrum. Feeding these changes into a solar cell simulator results in a 29.7% increase in the power output for a typical triple-junction photovoltaic cell, with around one-third of the increase arising from enhanced cell efficiency due to improved spectral matching. Our estimates imply that these increases in power and cell efficiency would have been realised over many parts of China during the lockdown period. This study thus demonstrates how a cleaner atmosphere may enable more efficient large scale solar energy generation. We conclude by setting our results in the context of future climate change mitigation and air pollution policies.
-
Journal articleToumi R, Wang S, 2021,
Recent migration of tropical cyclones toward coasts
, Science, Vol: 371, Pages: 514-517, ISSN: 0036-8075Poleward migrations of tropical cyclones have been observed globally, but their impact on coastal areas remains unclear. We investigated the change in global tropical cyclone activity in coastal regions over the period 1982–2018. We found that the distance of tropical cyclone maximum intensity to land has decreased by about 30 kilometers per decade, and that the annual frequency of global tropical cyclones increases with proximity to land by about two additional cyclones per decade. Trend analysis reveals a robust migration of tropical cyclone activity toward coasts, concurrent with poleward migration of cyclone locations as well as a statistically significant westward shift. This zonal shift of tropical cyclone tracks may be mainly driven by global zonal changes in environmental steering flow.
-
Journal articleBowen TA, Bale SD, Bandyopadhyay R, et al., 2021,
Kinetic-Scale Turbulence in the Venusian Magnetosheath
, GEOPHYSICAL RESEARCH LETTERS, Vol: 48, ISSN: 0094-8276- Cite
- Citations: 13
-
Journal articleHeiter U, Lind K, Bergemann M, et al., 2021,
Atomic data for the Gaia-ESO Survey
, ASTRONOMY & ASTROPHYSICS, Vol: 645, ISSN: 0004-6361- Cite
- Citations: 70
-
Journal articleGunell H, Goetz C, Odelstad E, et al., 2021,
Ion acoustic waves near a comet nucleus: Rosetta observations at comet 67P/Churyumov-Gerasimenko
, ANNALES GEOPHYSICAE, Vol: 39, Pages: 53-68, ISSN: 0992-7689 -
Conference paperSaboya E, Zazzeri G, Graven H, et al., 2021,
Continuous CH₄ and δ¹³CH₄ Measurements in London Demonstrate Under-Reported Natural Gas Leakage
-
Conference paperPark J, Park B, Jeon S, et al., 2021,
Seamlessly integrated multi-modal imaging system through transparent ultrasound transducer in vivo
, ISSN: 1605-7422Multi-modal imaging technique has significantly spotlighted since it can provide a variety of information by combining the complementary merits of several single-modal imaging. In particular, in order to compensate for each shortcoming and improve image quality, an integrated optical and ultrasonic imaging system is being actively researched. However, the non-transparency of the ultrasound transducer made it difficult to integrate the optical and ultrasound imaging system. In previous study, we introduced the transparent ultrasound transducer (TUT) and dual-modal photoacoustic imaging (PAI)/ultrasound imaging (USI) system using the TUT. In this study, we present the multi-modal imaging system integrated with PA, US and optical coherence tomography (OCT). OCT has the advantage of acquiring anatomical information at optical resolution under subsurface and transparent media. To explore the usefulness of the multi-modal imaging system, we have successfully performed in vivo animal experiments: 1) eye imaging experiments and 2) subcutaneous melanoma imaging. In PAI, blood vessels and melanoma are clearly visualized. In OCT, the morphological information in shallow depth are observed in detail. In USI, the melanoma boundary and surrounding tissues are clearly confirmed. These results show that TUT based multi-modal imaging system can serve as a comprehensive in various applications.
-
Book chapterDunlop MW, Wang TY, Dong XC, et al., 2021,
Multispacecraft Measurements in the Magnetosphere
, Magnetospheres in the Solar System, Pages: 637-656This chapter covers a selection of the range of multispacecraft techniques that have been initially developed to analyze Cluster data. We begin the chapter with a short introduction, following this with an account of the methods and their application. The topics are separated into those dealing with magnetic field gradients and topology (which include the curlometer, magnetic rotation analysis, and least squares approach); magnetic field reconstruction and the analysis of magnetic field nulls (which are significant for magnetic reconnection and other geometries); time series analysis, adapted for multispacecraft data (including boundary identification, dimensional, and motion analysis); and wave vector analysis methods in the Fourier domain.
-
Journal articleStawarz JE, Matteini L, Parashar TN, et al., 2021,
Comparative analysis of the various generalized Ohm's law terms in magnetosheath turbulence as observed by magnetospheric multiscale
, Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-14, ISSN: 2169-9380Decomposing the electric field (E) into the contributions from generalized Ohm's law provides key insight into both nonlinear and dissipative dynamics across the full range of scales within a plasma. Using high‐resolution, multi‐spacecraft measurements of three intervals in Earth's magnetosheath from the Magnetospheric Multiscale mission, the influence of the magnetohydrodynamic, Hall, electron pressure, and electron inertia terms from Ohm's law, as well as the impact of a finite electron mass, on the turbulent E spectrum are examined observationally for the first time. The magnetohydrodynamic, Hall, and electron pressure terms are the dominant contributions to E over the accessible length scales, which extend to scales smaller than the electron inertial length at the greatest extent, with the Hall and electron pressure terms dominating at sub‐ion scales. The strength of the non‐ideal electron pressure contribution is stronger than expected from linear kinetic Alfvén waves and a partial anti‐alignment with the Hall electric field is present, linked to the relative importance of electron diamagnetic currents in the turbulence. The relative contribution of linear and nonlinear electric fields scale with the turbulent fluctuation amplitude, with nonlinear contributions playing the dominant role in shaping E for the intervals examined in this study. Overall, the sum of the Ohm's law terms and measured E agree to within ∼ 20% across the observable scales. These results both confirm general expectations about the behavior of E in turbulent plasmas and highlight features that should be explored further theoretically.
-
Journal articleHanna E, Cappelen J, Fettweis X, et al., 2021,
Greenland surface air temperature changes from 1981 to 2019 and implications for ice-sheet melt and mass-balance change
, INTERNATIONAL JOURNAL OF CLIMATOLOGY, Vol: 41, Pages: E1336-E1352, ISSN: 0899-8418- Cite
- Citations: 96
-
Journal articleLiggins FS, Pickering JC, Nave G, et al., 2021,
The Spectrum and Term Analysis of Singly Ionized Manganese
, ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 252, ISSN: 0067-0049- Cite
- Citations: 5
-
Journal articleBallinger TJ, Hanna E, Hall RJ, et al., 2021,
The role of blocking circulation and emerging open water feedbacks on Greenland cold-season air temperature variability over the last century
, INTERNATIONAL JOURNAL OF CLIMATOLOGY, Vol: 41, Pages: E2778-E2800, ISSN: 0899-8418- Cite
- Citations: 8
-
Journal articleHall RJ, Hanna E, Chen L, 2021,
Winter Arctic Amplification at the synoptic timescale, 1979-2018, its regional variation and response to tropical and extratropical variability
, CLIMATE DYNAMICS, Vol: 56, Pages: 457-473, ISSN: 0930-7575- Cite
- Citations: 15
-
Book chapterSouthwood DJ, 2021,
A Brief History of the Magnetosphere
, MAGNETOSPHERES IN THE SOLAR SYSTEM, Editors: Maggiolo, Andre, Hasegawa, Welling, Zhang, Paxton, Publisher: AMER GEOPHYSICAL UNION, Pages: 3-13, ISBN: 978-1-119-50752-9 -
Book chapterNilsson H, Behar E, Burch JL, et al., 2021,
Birth of a Magnetosphere
, MAGNETOSPHERES IN THE SOLAR SYSTEM, Editors: Maggiolo, Andre, Hasegawa, Welling, Zhang, Paxton, Publisher: AMER GEOPHYSICAL UNION, Pages: 427-439, ISBN: 978-1-119-50752-9- Author Web Link
- Cite
- Citations: 2
-
Conference paperKromyda L, Malaspina DM, Ergun RE, et al., 2021,
Electrostatic Waves with Rapid Frequency Shifts in the Solar Wind from PSP observations
, United-States-National-Committee-of-URSI National Radio Science Meeting (USNC-URSI NRSM), Publisher: IEEE, Pages: 220-221 -
Book chapterKeeling RF, Graven HD, 2021,
Insights from Time Series of Atmospheric Carbon Dioxide and Related Tracers
, ANNUAL REVIEW OF ENVIRONMENT AND RESOURCES, VOL 46, 2021, Editors: Gadgil, Tomich, Publisher: ANNUAL REVIEWS, Pages: 85-110- Cite
- Citations: 12
-
Journal articleEastwood JP, Goldman M, Phan TD, et al., 2020,
Energy flux densities near the electron dissipation region in asymmetric magnetopause reconnection
, Physical Review Letters, Vol: 125, Pages: 1-6, ISSN: 0031-9007Magnetic reconnection is of fundamental importance to plasmas because of its role in releasing and repartitioning stored magnetic energy. Previous results suggest that this energy is predominantly released as ion enthalpy flux along the reconnection outflow. Using Magnetospheric Multiscale data we find the existence of very significant electron energy flux densities in the vicinity of the magnetopause electron dissipation region, orthogonal to the ion energy outflow. These may significantly impact models of electron transport, wave generation, and particle acceleration.
-
Journal articleFletcher LN, Simon AA, Hofstadter MD, et al., 2020,
Ice giant system exploration in the 2020s: an introduction
, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 378, Pages: 1-11, ISSN: 1364-503XThe international planetary science community met in London in January 2020, united in the goal of realizing the first dedicated robotic mission to the distant ice giants, Uranus and Neptune, as the only major class of solar system planet yet to be comprehensively explored. Ice-giant-sized worlds appear to be a common outcome of the planet formation process, and pose unique and extreme tests to our understanding of exotic water-rich planetary interiors, dynamic and frigid atmospheres, complex magnetospheric configurations, geologically-rich icy satellites (both natural and captured), and delicate planetary rings. This article introduces a special issue on ice giant system exploration at the start of the 2020s. We review the scientific potential and existing mission design concepts for an ambitious international partnership for exploring Uranus and/or Neptune in the coming decades.
-
Journal articleMalik A, Nowack PJ, Haigh JD, et al., 2020,
Tropical Pacific climate variability under solar geoengineering: impacts on ENSO extremes
, ATMOSPHERIC CHEMISTRY AND PHYSICS, Vol: 20, Pages: 15461-15485, ISSN: 1680-7316 -
Journal articleMatteini L, Franci L, Alexandrova O, et al., 2020,
Magnetic field turbulence in the solar wind at sub-ion scales: in situ observations and numerical simulations
, Frontiers in Astronomy and Space Sciences, ISSN: 2296-987XWe investigate the transition of the solar wind turbulent cascade from MHD tosub-ion range by means of a detail comparison between in situ observations andhybrid numerical simulations. In particular we focus on the properties of themagnetic field and its component anisotropy in Cluster measurements and hybrid2D simulations. First, we address the angular distribution of wave-vectors inthe kinetic range between ion and electron scales by studying the varianceanisotropy of the magnetic field components. When taking into account thesingle-direction sampling performed by spacecraft in the solar wind, the mainproperties of the fluctuations observed in situ are also recovered in ournumerical description. This result confirms that solar wind turbulence in thesub-ion range is characterized by a quasi-2D gyrotropic distribution ofk-vectors around the mean field. We then consider the magnetic compressibilityassociated with the turbulent cascade and its evolution from large-MHD tosub-ion scales. The ratio of field-aligned to perpendicular fluctuations,typically low in the MHD inertial range, increases significantly when crossingion scales and its value in the sub-ion range is a function of the total plasmabeta only, as expected from theoretical predictions, with higher magneticcompressibility for higher beta. Moreover, we observe that this increase has agradual trend from low to high beta values in the in situ data; this behaviouris well captured by the numerical simulations. The level of magnetic fieldcompressibility that is observed in situ and in the simulations is in fairlygood agreement with theoretical predictions, especially at high beta,suggesting that in the kinetic range explored the turbulence is supported bylow-frequency and highly-oblique fluctuations in pressure balance, like kineticAlfv\'en waves or other slowly evolving coherent structures.
-
Journal articleQuaas J, Arola A, Cairns B, et al., 2020,
Constraining the Twomey effect from satellite observations: Issues and perspectives
, Atmospheric Chemistry and Physics, Vol: 20, Pages: 15079-15099, ISSN: 1680-7316The Twomey effect describes the radiative forcing associated with a change in cloud albedo due to an increase in anthropogenic aerosol emissions. It is driven by the perturbation in cloud droplet number concentration (ΔNd, ant) in liquid-water clouds and is currently understood to exert a cooling effect on climate. The Twomey effect is the key driver in the effective radiative forcing due to aerosol–cloud interactions, but rapid adjustments also contribute. These adjustments are essentially the responses of cloud fraction and liquid water path to ΔNd, ant and thus scale approximately with it. While the fundamental physics of the influence of added aerosol particles on the droplet concentration (Nd) is well described by established theory at the particle scale (micrometres), how this relationship is expressed at the large-scale (hundreds of kilometres) perturbation, ΔNd, ant, remains uncertain. The discrepancy between process understanding at particle scale and insufficient quantification at the climate-relevant large scale is caused by co-variability of aerosol particles and updraught velocity and by droplet sink processes. These operate at scales on the order of tens of metres at which only localised observations are available and at which no approach yet exists to quantify the anthropogenic perturbation. Different atmospheric models suggest diverse magnitudes of the Twomey effect even when applying the same anthropogenic aerosol emission perturbation. Thus, observational data are needed to quantify and constrain the Twomey effect. At the global scale, this means satellite data. There are four key uncertainties in determining ΔNd, ant, namely the quantification of (i) the cloud-active aerosol – the cloud condensation nuclei (CCN) concentrations at or above cloud base, (ii) Nd, (iii) the statistical approach for inferring the sensitivity of Nd to aerosol particles from the satellite data and (iv) uncert
-
Journal articleSchwartz SJ, Kucharek H, Farrugia CJ, et al., 2020,
Energy Conversion within Current Sheets in the Earth's Quasi-parallel Magnetosheath
-
Journal articlePucci F, Velli M, Shi C, et al., 2020,
Onset of fast magnetic reconnection and particle energization in laboratory and space plasmas
, JOURNAL OF PLASMA PHYSICS, Vol: 86, ISSN: 0022-3778- Cite
- Citations: 13
-
Journal articleSouthwood D, Kivelson M, 2020,
An improbable collaboration
, Journal of Geophysical Research: Space Physics, Vol: 125, ISSN: 2169-9380Fifty years of collaboration between the authors are reviewed. Common themes cover magnetospheric magnetohydrodynamic phenomena: MHD waves, wave‐particle interactions, circulation, global modes and field line resonances in the terrestrial context, and magnetosphere‐moon interactions, transport processes, instabilities and global structure in the magnetospheres of giant planets. Over the period reviewed, instrumentation has improved, particularly in particle detectors, and interpretations that seemed radical when first suggested are now supported by measurements and seem commonplace.
-
Journal articleGoldman MV, Newman DL, Eastwood JP, et al., 2020,
Multibeam energy moments of multibeam particle velocity distributions
, Journal of Geophysical Research: Space Physics, Vol: 125, Pages: 1-19, ISSN: 2169-9380High‐resolution electron and ion velocity distributions, f(v), which consist of N effectively disjoint beams, have been measured by NASA's Magnetospheric Multiscale Mission and in reconnection simulations. Commonly used standard velocity moments assume a single mean‐flow velocity for the entire distribution. This can lead to counterintuitive results for a multibeam f(v). An example is the standard thermal energy density moment (at a given space‐time point) of a pair of equal and opposite cold particle beams. This standard moment is nonzero even though each beam has zero thermal energy density. By contrast, a multibeam moment of two or more cold beams at a given position and time has no thermal energy. A multibeam moment is obtained by taking a standard moment of each beam and then summing over beams. In this paper we will generalize these notions, explore their consequences, and apply them to an f(v) which is a sum of tri‐Maxwellians. Both standard and multibeam energy moments have coherent and incoherent pieces. Examples of incoherent moments are the thermal energy density, the pressure, and the thermal energy flux (enthalpy flux plus heat flux). Corresponding coherent moments are the bulk kinetic energy density, the ram pressure, and the bulk kinetic energy flux. The difference between a standard incoherent moment and its multibeam counterpart will be defined as the “pseudothermal part” of the standard moment. The sum of a pair of corresponding coherent and incoherent moments is the undecomposed moment. Undecomposed standard moments are always equal to the corresponding undecomposed multibeam moments.
-
Journal articleDing M, Pickering JC, 2020,
Measurements of the hyperfine structure of atomic energy levels in Co ii
, Astrophysical Journal Supplement Series, Vol: 251, Pages: 1-7, ISSN: 0067-0049Analysis of hyperfine structure constants of singly ionized cobalt (Co II) were performed on cobalt spectra measured by Fourier transform spectrometers in the region 3000–63,000 cm−1 (33333 – 1587 Å). Fits to over 700 spectral lines led to measurements of 292 magnetic dipole hyperfine interaction A constants, with values between −32.5 mK and 59.5 mK (1 mK = 0.001 cm−1). Uncertainties of 255 A constants were between ±0.4 mK and ±3.0 mK, the remaining 37 ranged up to ±7 mK. The electric quadrupole hyperfine interaction B constant could be estimated for only one energy level. The number of Co II levels with known A values has now increased tenfold, improving and enabling the wider, more reliable, and accurate application of Co II in astronomical chemical abundance analyses.
-
Journal articlePalchetti L, Brindley H, Bantges R, et al., 2020,
FORUM: unique far-infrared satellite observations to better understand how Earth radiates energy to space
, Bulletin of the American Meteorological Society, Vol: 101, Pages: E2030-E2046, ISSN: 0003-0007The Outgoing Longwave Radiation (OLR) emitted to space is a fundamental component of the Earth’s energy budget. There are numerous, entangled physical processes that contribute to OLR and that are responsible for driving, and responding to, climate change. Spectrally-resolved observations can disentangle these processes, but technical limitations have precluded accurate space-based spectral measurements covering the far-infrared (FIR) from 100 to 667 cm−1 (wavelengths between 15 and 100 μm). The Earth’s FIR spectrum is thus essentially unmeasured even though at least half of the OLR arises from this spectral range. The region is strongly influenced by upper tropospheric/lower stratospheric water vapor, temperature lapse rate, ice cloud distribution and microphysics, all critical parameters in the climate system that are highly variable and still poorly observed and understood. To cover this uncharted territory in Earth observations, the Far-infrared Outgoing RadiationUnderstanding and Monitoring (FORUM) mission has recently been selected as ESA’s 9th Earth Explorer mission for launch in 2026. The primary goal of FORUM is to measure, with high absolute accuracy, the FIR component of the spectrally-resolved OLR for the first time with high spectral resolution and radiometric accuracy. The mission will provide a benchmark dataset of global observations which will significantly enhance our understanding of key forcing and feedback processes of the Earth’s atmosphere to enable more stringent evaluation of climate models. This paper describes the motivation for the mission, highlighting the scientific advances that are expected from the new measurements.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.