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Journal articleQuaas J, Gryspeerdt E, Vautard R, et al., 2021,
Climate impact of aircraft-induced cirrus assessed from satellite observations before and during COVID-19
, Environmental Research Letters, Vol: 16, Pages: 1-6, ISSN: 1748-9326Aircraft produce condensation trails, which are thought to increase high-level cloudiness under certain conditions. Howeverthe magnitude of such an effect and whether this contributes substantially to the radiative forcing due to the aviation sectorremain uncertain. The very substantial, near-global reduction in air traffic in response to the COVID-19 outbreak offers anunprecedented opportunity to identify the anthropogenic contribution to the observed cirrus coverage and thickness. Here weshow, using an analysis of satellite observations for the period March-May 2020, that in the 20% of the Northern Hemispheremid-latitudes with the largest air traffic reduction, cirrus fraction was reduced by ~9 ± 1.5% on average, and cirrus emissivitywas reduced by ~2 ±5% relative to what they should have been with normal air traffic. The changes are corroborated by aconsistent estimate based on linear trends over the period 2011 – 2019. The change in cirrus translates to a global radiativeforcing of 61 ±39 mWm-2. This estimate is somewhat smaller than previous assessments.
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Journal articleCattell C, Glesener L, Leiran B, et al., 2021,
Periodicities in an active region correlated with Type Ill radio bursts observed by Parker Solar Probe
, ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361- Cite
- Citations: 9
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Journal articleStansby D, Bercic L, Matteini L, et al., 2021,
Sensitivity of solar wind mass flux to coronal temperature
, ASTRONOMY & ASTROPHYSICS, Vol: 650, ISSN: 0004-6361 -
Journal articleZhang Z, Desai R, Miyake Y, et al., 2021,
Particle-in-cell simulations of the Cassini spacecraft’s interaction with Saturn’s ionosphere during the Grand Finale
, Monthly Notices of the Royal Astronomical Society, Vol: 504, Pages: 964-973, ISSN: 0035-8711A surprising and unexpected phenomenon observed during Cassini’s Grand Finale was the spacecraft charging to positive potentials in Saturn’s ionosphere. Here, the ionospheric plasma was depleted of free electrons with negatively charged ions and dust accumulating up to over 95 per cent of the negative charge density. To further understand the spacecraft–plasma interaction, we perform a three-dimensional Particle-In-Cell study of a model Cassini spacecraft immersed in plasma representative of Saturn’s ionosphere. The simulations reveal complex interaction features such as electron wings and a highly structured wake containing spacecraft-scale vortices. The results show how a large negative ion concentration combined with a large negative to positive ion mass ratio is able to drive the spacecraft to the observed positive potentials. Despite the high electron depletions, the electron properties are found as a significant controlling factor for the spacecraft potential together with the magnetic field orientation which induces a potential gradient directed across Cassini’s asymmetric body. This study reveals the global spacecraft interaction experienced by Cassini during the Grand Finale and how this is influenced by the unexpected negative ion and dust populations.
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Journal articleDesai RT, Zhang Z, Wu X, et al., 2021,
Photodetachment and Test-particle Simulation Constraints on Negative Ions in Solar System Plasmas
, The Planetary Science Journal, Vol: 2, Pages: 99-99<jats:title>Abstract</jats:title> <jats:p>Negative ions have been detected in abundance in recent years by spacecraft across the solar system. These detections were, however, made by instruments not designed for this purpose and, as such, significant uncertainties remain regarding the prevalence of these unexpected plasma components. In this article, the phenomenon of photodetachment is examined, and experimentally and theoretically derived cross-sections are used to calculate photodetachment rates for a range of atomic and molecular negative ions subjected to the solar photon spectrum. These rates are applied to negative ions outflowing from Europa, Enceladus, Titan, Dione, and Rhea and their trajectories are traced to constrain source production rates and the extent to which negative ions are able to pervade the surrounding space environments. Predictions are also made for further negative ion populations in the outer solar system with Triton used as an illustrative example. This study demonstrates how, at increased heliocentric distances, negative ions can form stable ambient plasma populations and can be exploited by future missions to the outer solar system.</jats:p>
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Journal articleStarkey MJ, Fuselier SA, Desai MI, et al., 2021,
MMS Observations of Energized He<SUP>+</SUP> Pickup Ions at Quasiperpendicular Shocks
, ASTROPHYSICAL JOURNAL, Vol: 913, ISSN: 0004-637X- Author Web Link
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- Citations: 2
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Journal articleWeiss Z, Concepcion-Mairey F, Pickering JC, et al., 2021,
Emission spectroscopic study of an analytical glow discharge with plane and hollow cathodes: Titanium and iron in argon discharge
, SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY, Vol: 180, ISSN: 0584-8547- Cite
- Citations: 2
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Journal articleJohlander A, Battarbee M, Vaivads A, et al., 2021,
Ion Acceleration Efficiency at the Earth's Bow Shock: Observations and Simulation Results
, ASTROPHYSICAL JOURNAL, Vol: 914, ISSN: 0004-637X- Author Web Link
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- Citations: 3
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Journal articleGonzalez CA, Tenerani A, Matteini L, et al., 2021,
Proton Energization by Phase Steepening of Parallel-propagating Alfvenic Fluctuations
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 914, ISSN: 2041-8205- Cite
- Citations: 7
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Journal articleSchwartz SJ, Ergun RE, Harald K, et al., 2021,
Evaluating the de Hoffmann-Teller cross-shock potential at real collisionless shocks
<jats:p>Shock waves are common in the heliosphere and beyond. The collisionlessnature of most astrophysical plasmas allows for the energy processed byshocks to be partitioned amongst particle sub-populations andelectromagnetic fields via physical mechanisms that are not wellunderstood. The electrostatic potential across such shocks is framedependent. In a frame where the incident bulk velocity is parallel tothe magnetic field, the deHoffmann-Teller frame, the potential is linkeddirectly to the ambipolar electric field established by the electronpressure gradient. Thus measuring and understanding this potentialsolves the electron partition problem, and gives insight into othercompeting shock processes. Integrating measured electric fields is spaceis problematic since the measurements can have offsets that change withplasma conditions. The offsets, once integrated, can be as large orlarger than the shock potential. Here we exploit the high-quality fieldand plasma measurements from NASA's Magnetospheric Multiscale mission toattempt this calculation. We investigate recent adaptations of thedeHoffmann-Teller frame transformation to include time variability, andconclude that in practise these face difficulties inherent in the 3Dtime-dependent nature of real shocks by comparison to 1D simulations.Potential estimates based on electron fluid and kinetic analyses providethe most robust measures of the deHoffmann-Teller potential, but withsome care direct integration of the electric fields can be made toagree. These results suggest that it will be difficult to independentlyassess the role of other processes, such as scattering by shockturbulence, in accounting for the electron heating.</jats:p>
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Journal articleKuhn-Régnier A, Voulgarakis A, Nowack P, et al., 2020,
Supplementary material to "Quantifying the Importance of Antecedent Fuel-Related VegetationProperties for Burnt Area using Random Forests"
, Biogeosciences, ISSN: 1726-4170 -
Journal articleTelloni D, Sorriso-Valvo L, Woodham LD, et al., 2021,
Evolution of solar wind turbulence from 0.1 to 1 au during the first parker solar probe-solar orbiter radial alignment
, Letters of the Astrophysical Journal, Vol: 912, Pages: 1-8, ISSN: 2041-8205The first radial alignment between Parker Solar Probe and Solar Orbiter spacecraft is used to investigate the evolution of solar wind turbulence in the inner heliosphere. Assuming ballistic propagation, two 1.5 hr intervals are tentatively identified as providing measurements of the same plasma parcels traveling from 0.1 to 1 au. Using magnetic field measurements from both spacecraft, the properties of turbulence in the two intervals are assessed. Magnetic spectral density, flatness, and high-order moment scaling laws are calculated. The Hilbert–Huang transform is additionally used to mitigate short sample and poor stationarity effects. Results show that the plasma evolves from a highly Alfvénic, less-developed turbulence state near the Sun, to fully developed and intermittent turbulence at 1 au. These observations provide strong evidence for the radial evolution of solar wind turbulence.
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Journal articleGaland M, Feldman PD, Bockelee-Morvan D, et al., 2021,
Far-ultraviolet aurora identified at comet 67P/Churyumov-Gerasimenko (vol 4, pg 1084, 2020)
, NATURE ASTRONOMY, ISSN: 2397-3366 -
Journal articleCheng IK, Achilleos N, Masters A, et al., 2021,
Electron bulk heating at Saturn's magnetopause
, Journal of Geophysical Research: Space Physics, Vol: 126, ISSN: 2169-9380Magnetic reconnection at the magnetopause (MP) energizes ambient plasma via the release of magnetic energy and produces an “open” magnetosphere allowing solar wind particles to directly enter the system. At Saturn, the nature of MP reconnection remains unclear. The current study examines electron bulk heating at MP crossings, in order to probe the relationship between observed and predicted reconnection heating proposed by Phan et al. (2013, https://doi.org/10.1002/grl.50917) under open and closed MP, and how this may pertain to the position of the crossings in the Δβ‐magnetic shear parameter space. The electron heating for 70 MP crossings made by the Cassini spacecraft from April 2005 to July 2007 was found using 1d and 3d moment methods. Minimum variance analysis was used on the magnetic field data to help indicate whether the MP is open or closed. We found better agreement between observed and predicted heating for events suggestive of locally “open” MP. For events suggestive of locally “closed” MP, we observed a cluster of points consistent with no electron heating, but also numerous cases with significant heating. Examining the events in the Δβ‐magnetic shear parameter space, we find 83% of events without evidence of energization were situated in the “reconnection suppressed” regime, whilst between 43% to 68% of events with energization lie in the “reconnection possible” regime depending on the threshold used. The discrepancies could be explained by a combination of spatial and temporal variability which makes it possible to observe heated electrons with different conditions from the putative reconnection site.
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Journal articleGibbins G, Haigh JD, 2021,
Comments on "global and regional entropy production by radiation Estimated from satellite observations"
, Journal of Climate, Vol: 34, Pages: 3721-3728, ISSN: 0894-8755A recent paper by Kato and Rose reports a negative correlation between the annual mean entropy production rate of the climate and the absorption of solar radiation in the CERES SYN1deg dataset, using the simplifying assumption that the system is steady in time. It is shown here, however, that when the nonsteady interannual storage of entropy is accounted for, the dataset instead implies a positive correlation; that is, global entropy production rates increase with solar absorption. Furthermore, this increase is consistent with the response demonstrated by an energy balance model and a radiative–convective model. To motivate this updated analysis, a detailed discussion of the conceptual relationship between entropy production, entropy storage, and entropy flows is provided. The storage-corrected estimate for the mean global rate of entropy production in the CERES dataset from all irreversible transfer processes is 81.9 mW m−2 K−1 and from only nonradiative processes is 55.2 mW m−2 K−1 (observations from March 2000 to February 2018).
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Journal articleLai T-K, Hendricks EA, Yau MK, et al., 2021,
Roles of Barotropic Instability across the Moat in Inner Eyewall Decay and Outer Eyewall Intensification: Essential Dynamics
, JOURNAL OF THE ATMOSPHERIC SCIENCES, Vol: 78, Pages: 1411-1428, ISSN: 0022-4928 -
Journal articleHoilijoki S, Pucci F, Ergun RE, et al., 2021,
Origin of Electron-Scale Magnetic Fluctuations Close to an Electron Diffusion Region
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380 -
Journal articleMartinovic MM, Klein KG, Huang J, et al., 2021,
Multiscale Solar Wind Turbulence Properties inside and near Switchbacks Measured by the Parker Solar Probe
, ASTROPHYSICAL JOURNAL, Vol: 912, ISSN: 0004-637X- Author Web Link
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- Citations: 30
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Journal articleMa B, Chen L, Wu D, et al., 2021,
Statistics of Low Frequency Cutoffs for Type III Radio Bursts Observed by Parker Solar Probe during Its Encounters 1-5
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 913, ISSN: 2041-8205- Cite
- Citations: 6
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Journal articleDiaz-Aguado MF, Bonnell JW, Bale SD, et al., 2021,
Parker Solar Probe FIELDS Instrument Charging in the Near Sun Environment: Part 2: Comparison of In-Flight Data and Modeling Results
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380- Author Web Link
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- Citations: 3
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Journal articleDiaz-Aguado MF, Bonnell JW, Bale SD, et al., 2021,
Parker Solar Probe FIELDS Instrument Charging in the Near Sun Environment: Part 1: Computational Model
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380- Author Web Link
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- Citations: 7
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Journal articleSong S, Choi Y-S, Jeon H, et al., 2021,
Gender Perspectives on Climate Change: A Review
, Journal of Climate Change Research, Vol: 12, Pages: 121-135, ISSN: 2093-5919 -
Journal articleNair V, Heus T, van Reeuwijk M, 2021,
A Lagrangian study of interfaces at the edges of cumulus clouds
, Journal of the Atmospheric Sciences, Vol: 78, Pages: 2397-2412, ISSN: 0022-4928Interfaces at the edge of an idealised, non-precipitating, warm cloud are studied using Direct Numerical Simulation (DNS) complemented with a Lagrangian particle tracking routine. Once a shell has formed, four zones can be distinguished: the cloud core, visible shell, invisible shell and the environment. The union of the visible and invisible regions is the shell commonly referred to in literature. The boundary between the invisible shell and the environment is the Turbulent-NonTurbulent Interface (TNTI) which is typically not considered in cloud studies. Three million particles were seeded homogeneously across the domain and properties were recorded along individual trajectories. The results demonstrate that the traditional cloud boundary (separating cloudy and non-cloudy regions using thresholds applied on liquid condensate or updraft velocity) are some distance away from the TNTI. Furthermore, there is no dynamic difference between the traditional liquid-condensate boundary and the region extending to the TNTI. However, particles crossing the TNTI exhibit a sharp jump in enstrophy and a smooth increase in buoyancy. The traditional cloud boundary coincides with the location of minimum buoyancy in the shell. The shell pre-mixes the entraining and detraining air and analysis reveals a highly skewed picture of entrainment and detrainment at the traditional cloud boundary. A preferential entrainment of particles with velocity and specific humidity higher than the mean values in the shell is observed. Large-eddy simulation of a more realistic setup detects an interface with similar properties using the same thresholds as in the DNS, indicating that the DNS results extrapolate beyond their idealised conditions.
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Journal articlePulupa M, Bale SD, Curry SM, et al., 2021,
Non-Detection of Lightning During the Second Parker Solar Probe Venus Gravity Assist
, GEOPHYSICAL RESEARCH LETTERS, Vol: 48, ISSN: 0094-8276- Author Web Link
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- Citations: 4
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Journal articleGryspeerdt E, Goren T, Smith T, 2021,
Observing the timescales of aerosol-cloud interactions in snapshot satellite images
, Atmospheric Chemistry and Physics, Vol: 21, Pages: 6093-6109, ISSN: 1680-7316The response of cloud processes to an aerosol perturbation is one of the largest uncertainties in the anthropogenic forcing of the climate. It occurs at a variety of timescales, from the near-instantaneous Twomey effect to the longer timescales required for cloud adjustments. Understanding the temporal evolution of cloud properties following an aerosol perturbation is necessary to interpret the results of so-called “natural experiments” from a known aerosol source such as a ship or industrial site. This work uses reanalysis wind fields and ship emission information matched to observations of ship tracks to measure the timescales of cloud responses to aerosol in instantaneous (or“snapshot”) images taken by polar-orbiting satellites.As in previous studies, the local meteorological environment is shown to have a strong impact on the occurrence and properties of ship tracks, but there is a strong time dependence in their properties. The largest droplet number concentration (Nd) responses are found within 3 h of emission, while cloud adjustments continue to evolve over periods of 10 h or more. Cloud fraction is increased within the early life of ship tracks, with the formation of ship tracks in otherwise clear skies indicating that around 5 %–10 % of clear-sky cases in this region may be aerosol-limited.The liquid water path (LWP) enhancement and the Nd–LWP sensitivity are also time dependent and strong functions of the background cloud and meteorological state. The near-instant response of the LWP within ship tracks may be evidence of a bias in estimates of the LWP response to aerosol derived from natural experiments. These results highlight the importance of temporal development and the background cloud field for quantifying the aerosol impact on clouds, even in situations where the aerosol perturbation is clear.
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Journal articleHeyner, Auster, Fornacon, et al., 2021,
The BepiColombo Planetary Magnetometer MPO-MAG: what can we Learn from the Hermean magnetic field?
, Space Science Reviews, Vol: 217, ISSN: 0038-6308The magnetometer instrument MPO-MAG on-board the Mercury Planetary Orbiter (MPO) of the BepiColombo mission en-route to Mercury is introduced, with its instrument design, its calibration and scientific targets. The instrument is comprised of two tri-axial fluxgate magnetometers mounted on a 2.9 m boom and are 0.8 m apart. They monitor the magnetic field with up to 128 Hz in a ±2048 nT range. The MPO will be injected into an initial 480×1500 km polar orbit (2.3 h orbital period). At Mercury, we will map the planetary magnetic field and determine the dynamo generated field and constrain the secular variation. In this paper, we also discuss the effect of the instrument calibration on the ability to improve the knowledge on the internal field. Furthermore, the study of induced magnetic fields and field-aligned currents will help to constrain the interior structure in concert with other geophysical instruments. The orbit is also well-suited to study dynamical phenomena at the Hermean magnetopause and magnetospheric cusps. Together with its sister instrument Mio-MGF on-board the second satellite of the BepiColombo mission, the magnetometers at Mercury will study the reaction of the highly dynamic magnetosphere to changes in the solar wind. In the extreme case, the solar wind might even collapse the entire dayside magnetosphere. During cruise, MPO-MAG will contribute to studies of solar wind turbulence and transient phenomena.
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Journal articleMackie A, Brindley HE, Palmer PI, 2021,
Contrasting observed atmospheric responses to tropical SST warming patterns
, Journal of Geophysical Research: Atmospheres, Vol: 126, Pages: 1-12, ISSN: 2169-897XEquilibrium climate sensitivity (ECS) is a theoretical concept which describes the change in global mean surface temperature that results from a sustained doubling of atmospheric CO2. Current ECS estimates range from ∼1.8 to 5.6 K, reflecting uncertainties in climate feedbacks. The sensitivity of the lower (1,000–700 hPa) and upper (500–200 hPa) troposphere to changes in spatial patterns of tropical sea surface temperature (SST) have been proposed by recent model studies as key feedbacks controlling climate sensitivity. We examine empirical evidence for these proposed mechanisms using 14 years of satellite data. We examine the response of temperature and humidity profiles, clouds, and top‐of‐the‐atmosphere radiation to relative warming in tropical ocean regions when there is either strong convection or subsidence. We find warmer SSTs in regions of strong subsidence are coincident with a decrease in lower tropospheric stability (−0.9 ± 0.4 KK−1) and low cloud cover (∼−6% K−1). This leads to a warming associated with the weakening in the shortwave cooling effect of clouds (4.2 ± 1.9 Wm−2K−1), broadly consistent with model calculations. In contrast, warmer SSTs in regions of strong convection are coincident with an increase in upper tropospheric humidity (3.2 ± 1.5% K−1). In this scenario, the dominant effect is the enhancement of the warming longwave cloud radiative effect (3.8 ± 3.0 Wm−2K−1) from an increase in high cloud cover (∼7% K−1), though changes in the net (longwave and shortwave) effect are not statistically significant (p < 0.003). Our observational evidence supports the existence of mechanisms linking contrasting atmospheric responses to patterns in SST, mechanisms which have been linked to climate sensitivity.
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Journal articleQu Y, Voulgarakis A, Wang T, et al., 2021,
A study of the effect of aerosols on surface ozone through meteorology feedbacks over China
, Atmospheric Chemistry and Physics, Vol: 21, Pages: 5705-5718, ISSN: 1680-7316Interactions between aerosols and gases in the atmosphere have been the focus of an increasing number of studies in recent years. Here, we focus on aerosol effects on tropospheric ozone that involve meteorological feedbacks induced by aerosol–radiation interactions. Specifically, we study the effects that involve aerosol influences on the transport of gaseous pollutants and on atmospheric moisture, both of which can impact ozone chemistry. For this purpose, we use the UK Earth System Model (UKESM1), with which we performed sensitivity simulations including and excluding the aerosol direct radiative effect (ADE) on atmospheric chemistry, and focused our analysis on an area with a high aerosol presence, namely China. By comparing the simulations, we found that ADE reduced shortwave radiation by 11 % in China and consequently led to lower turbulent kinetic energy, weaker horizontal winds and a shallower boundary layer (with a maximum of 102.28 m reduction in north China). On the one hand, the suppressed boundary layer limited the export and diffusion of pollutants and increased the concentration of CO, SO2, NO, NO2, PM2.5 and PM10 in the aerosol-rich regions. The NO/NO2 ratio generally increased and led to more ozone depletion. On the other hand, the boundary layer top acted as a barrier that trapped moisture at lower altitudes and reduced the moisture at higher altitudes (the specific humidity was reduced by 1.69 % at 1493 m on average in China). Due to reduced water vapour, fewer clouds were formed and more sunlight reached the surface, so the photolytical production of ozone increased. Under the combined effect of the two meteorology feedback methods, the annual average ozone concentration in China declined by 2.01 ppb (6.2 %), which was found to bring the model into closer agreement with surface ozone measurements from different parts of China.
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Journal articleDel Zanna G, Andretta V, Cargill PJ, et al., 2021,
High resolution soft X-ray spectroscopy and the quest for the hot (5-10 MK) plasma in solar active regions
, Frontiers in Astronomy and Space Sciences, Vol: 8, Pages: 1-19, ISSN: 2296-987XWe discuss the diagnostics available to study the 5–10 MK plasma in the solar corona, which is key to understanding the heating in the cores of solar active regions. We present several simulated spectra, and show that excellent diagnostics are available in the soft X-rays, around 100 Å, as six ionization stages of Fe can simultaneously be observed, and electron densities derived, within a narrow spectral region. As this spectral range is almost unexplored, we present an analysis of available and simulated spectra, to compare the hot emission with the cooler component. We adopt recently designed multilayers to present estimates of count rates in the hot lines, with a baseline spectrometer design. Excellent count rates are found, opening up the exciting opportunity to obtain high-resolution spectroscopy of hot plasma.
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Journal articleArcher MO, 2021,
Schools of all backgrounds can do physics research – on the accessibility and equity of the Physics Research in School Environments (PRiSE) approach to independent research projects
, Geoscience Communication, Vol: 4, Pages: 189-208, ISSN: 2569-7110Societal biases are a major issue in school students' access to and interaction with science. School engagement programmes in science from universities, like independent research projects, which could try and tackle these problems are, however, often inequitable. We evaluate these concerns applied to one such programme, Physics Research in School Environments (PRiSE), which features projects in space science, astronomy, and particle physics. Comparing the schools involved with PRiSE to those of other similar schemes and UK national statistics, we find that PRiSE has engaged a much more diverse set of schools with significantly more disadvantaged groups than is typical. While drop-off occurs within the protracted programme, we find no evidence of systematic biases present. The majority of schools that complete projects return for multiple years with the programme, with this repeated buy-in from schools again being unpatterned by typical societal inequalities. Therefore, a school's ability to succeed in independent research projects appears independent of background within the PRiSE framework. Qualitative feedback from teachers shows that the diversity and equity of the programme, which they attribute to the level of support offered through PRiSE's framework, is valued, and they have highlighted further ways of making the projects potentially even more accessible. Researcher involvement, uncommon in many other programmes, along with teacher engagement and communication are found to be key elements to success in independent research projects overall.
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