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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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Journal articleArcher MO, DeWitt J, 2021,
“Thanks for helping me find my enthusiasm for physics”: the lasting impacts “research in schools” projects can have on students, teachers, and schools
, Geoscience Communication, Vol: 4, Pages: 169-188, ISSN: 2569-7110Using 6 years of evaluation data, we assess the medium- and long-term impacts upon a diverse range of students, teachers, and schools from participating in a programme of protracted university-mentored projects based on cutting-edge space science, astronomy, and particle physics research. After having completed their 6-month-long projects, the 14–18-year-old school students report having substantially increased in confidence relating to relevant scientific topics and methods as well as having developed numerous skills, outcomes which are corroborated by teachers. There is evidence that the projects helped increase students' aspirations towards physics, whereas science aspirations (generally high to begin with) were typically maintained or confirmed through their involvement. Longitudinal evaluation 3 years later has revealed that these projects have been lasting experiences for students which they have benefited from and drawn upon in their subsequent university education. Data on students' destinations suggest that their involvement in research projects has made them more likely to undertake physics and STEM degrees than would otherwise be expected. Cases of co-created novel physics research resulting from Physics Research in School Environments (PRiSE) has also seemed to have a powerful effect, not only on the student co-authors, but also participating students from other schools. Teachers have also been positively affected through participating, with the programme having influenced their own knowledge, skills, and pedagogy, as well as having advantageous effects felt across their wider schools. These impacts suggest that similar “research in schools” initiatives may have a role to play in aiding the increased uptake and diversity of physics and/or STEM in higher education as well as meaningfully enhancing the STEM environment within schools.
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Journal articleArcher MO, DeWitt J, Thorley C, et al., 2021,
Evaluating participants' experience of extended interaction with cutting-edge physics research through the PRiSE “research in schools” programme
, Geoscience Communication, Vol: 4, Pages: 147-168, ISSN: 2569-7110Physics in schools is distinctly different from, and struggles to capture the excitement of, university research-level work. Initiatives where students engage in independent research linked to cutting-edge physics within their school over several months might help mitigate this, potentially facilitating the uptake of science in higher education. However, how such initiatives are best supported remains unclear and understudied. This paper evaluates a provision framework, Physics Research in School Environments (PRiSE), using survey data from participating 14–18-year-old students and their teachers to understand their experience of the programme. The results show that PRiSE appears to provide much more positive experiences than typical university outreach initiatives due to the nature of the opportunities afforded over several months, which schools would not be able to provide without external input. The intensive support offered is deemed necessary, with all elements appearing equally important. Based on additional feedback from independent researchers and engagement professionals, we also suggest the framework could be adopted at other institutions and applied to their own areas of scientific research, something which has already started to occur.
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Journal articleTurner DL, Wilson LB, Goodrich KA, et al., 2021,
Direct multipoint observations capturing the reformation of a supercritical fast magnetosonic shock
, The Astrophysical Journal Letters, Vol: 911, Pages: 1-11, ISSN: 2041-8205Using multipoint Magnetospheric Multiscale (MMS) observations in an unusual string-of-pearls configuration, we examine in detail observations of the reformation of a fast magnetosonic shock observed on the upstream edge of a foreshock transient structure upstream of Earth's bow shock. The four MMS spacecraft were separated by several hundred kilometers, comparable to suprathermal ion gyroradius scales or several ion inertial lengths. At least half of the shock reformation cycle was observed, with a new shock ramp rising up out of the "foot" region of the original shock ramp. Using the multipoint observations, we convert the observed time-series data into distance along the shock normal in the shock's rest frame. That conversion allows for a unique study of the relative spatial scales of the shock's various features, including the shock's growth rate, and how they evolve during the reformation cycle. Analysis indicates that the growth rate increases during reformation, electron-scale physics play an important role in the shock reformation, and energy conversion processes also undergo the same cyclical periodicity as reformation. Strong, thin electron-kinetic-scale current sheets and large-amplitude electrostatic and electromagnetic waves are reported. Results highlight the critical cross-scale coupling between electron-kinetic- and ion-kinetic-scale processes and details of the nature of nonstationarity, shock-front reformation at collisionless, fast magnetosonic shocks.
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Journal articleHellinger P, Verdini A, Landi S, et al., 2021,
Scale dependence and cross-scale transfer of kinetic energy in compressible hydrodynamic turbulence at moderate Reynolds numbers
, PHYSICAL REVIEW FLUIDS, Vol: 6, ISSN: 2469-990XWe investigate the properties of the scale dependence and cross-scale transfer of kinetic energy in compressible three-dimensional hydrodynamic turbulence by means of two direct numerical simulations of decaying turbulence with initial Mach numbers 𝑀=1/3 and 1, and with moderate Reynolds numbers, 𝑅𝜆∼100. The turbulent dynamics is analyzed using compressible and incompressible versions of the dynamic spectral transfer (ST) and the Kármán-Howarth-Monin (KHM) equations. We find that the nonlinear coupling leads to a flux of the kinetic energy to small scales where it is dissipated; at the same time, the reversible pressure-dilatation mechanism causes oscillatory exchanges between the kinetic and internal energies with an average zero net energy transfer. While the incompressible KHM and ST equations are not generally valid in the simulations, their compressible counterparts are well satisfied and describe, in a quantitatively similar way, the decay of the kinetic energy on large scales, the cross-scale energy transfer/cascade, the pressure dilatation, and the dissipation. There exists a simple relationship between the KHM and ST results through the inverse proportionality between the wave vector 𝑘 and the spatial separation length 𝑙 as 𝑘𝑙≃√3. For a given time, the dissipation and pressure-dilatation terms are strong on large scales in the KHM approach, whereas the ST terms become dominant on small scales; this is due to the complementary cumulative behavior of the two methods. The effect of pressure dilatation is weak when averaged over a period of its oscillations and may lead to a transfer of the kinetic energy from large to small scales without a net exchange between the kinetic and internal energies. Our results suggest that for large-enough systems, there exists an inertial range for the kinetic energy cascade. This transfer is partly due to the classical, nonlinear advection-driven cascade and partly due to the pressure dilatation-
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Journal articleChandra N, Patra PK, Bisht JSH, et al., 2021,
Emissions from the Oil and Gas Sectors, Coal Mining and Ruminant Farming Drive Methane Growth over the Past Three Decades
, JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN, Vol: 99, Pages: 309-337, ISSN: 0026-1165- Author Web Link
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- Citations: 48
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Journal articleHoraites K, Andersson L, Schwartz SJ, et al., 2021,
Observations of Energized Electrons in the Martian Magnetosheath
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380- Author Web Link
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- Citations: 4
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Journal articleCattell C, Breneman A, Dombeck J, et al., 2021,
Parker Solar Probe Evidence for Scattering of Electrons in the Young Solar Wind by Narrowband Whistler-mode Waves
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 911, ISSN: 2041-8205- Author Web Link
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- Citations: 33
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Journal articleHapgood M, Angling MJ, Attrill G, et al., 2021,
Development of space weather reasonable worst‐case scenarios for the UK national risk assessment
, Space Weather, Vol: 19, Pages: 1-32, ISSN: 1542-7390Severe space weather was identified as a risk to the UK in 2010 as part of a wider review of natural hazards triggered by the societal disruption caused by the eruption of the Eyjafjallajökull volcano in April of that year. To support further risk assessment by government officials, and at their request, we developed a set of reasonable worst‐case scenarios and first published them as a technical report in 2012 (current version published in 2020). Each scenario focused on a space weather environment that could disrupt a particular national infrastructure such as electric power or satellites, thus, enabling officials to explore the resilience of that infrastructure against severe space weather through discussions with relevant experts from other parts of government and with the operators of that infrastructure. This approach also encouraged us to focus on the environmental features that are key to generating adverse impacts. In this paper, we outline the scientific evidence that we have used to develop these scenarios, and the refinements made to them as new evidence emerged. We show how these scenarios are also considered as an ensemble so that government officials can prepare for a severe space weather event, during which many or all of the different scenarios will materialize. Finally, we note that this ensemble also needs to include insights into how public behavior will play out during a severe space weather event and hence the importance of providing robust, evidence‐based information on space weather and its adverse impacts.
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Journal articleChhiber R, Matthaeus WH, Bowen TA, et al., 2021,
Subproton-scale Intermittency in Near-Sun Solar Wind Turbulence Observed by the Parker Solar Probe
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 911, ISSN: 2041-8205- Author Web Link
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- Citations: 45
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Journal articleRobertson SL, Eastwood JP, Stawarz JE, et al., 2021,
Electron trapping in magnetic mirror structures at the edge of magnetopause flux ropes
, Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-17, ISSN: 2169-9380Flux ropes are a proposed site for particle energization during magnetic reconnection, with several mechanisms proposed. Here, Magnetospheric Multiscale mission observations of magnetic mirror structures on the edge of two ion‐scale magnetopause flux ropes are presented. Donut‐shaped features in the electron pitch angle distributions provide evidence for electron trapping in the structures. Furthermore, both events show trapping with extended 3D structure along the body of the flux rope. Potential formation mechanisms, such as the magnetic mirror instability, are examined and the evolutionary states of the structures are compared. Pressure and force analysis suggest that such structures could provide an important electron acceleration mechanism for magnetopause flux ropes, and for magnetic reconnection more generally.
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Journal articleBurns JO, MacDowall R, Bale S, et al., 2021,
Low Radio Frequency Observations from the Moon Enabled by NASA Landed Payload Missions
, PLANETARY SCIENCE JOURNAL, Vol: 2- Cite
- Citations: 25
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Journal articleStaniland NR, Dougherty MK, Masters A, et al., 2021,
The cushion region and dayside magnetodisc structure at Saturn
, Geophysical Research Letters, Vol: 48, Pages: 1-9, ISSN: 0094-8276A sustained quasi‐dipolar magnetic field between the current sheet outer edge and the magnetopause, known as a cushion region, has previously been observed at Jupiter, but not yet at Saturn. Using the complete Cassini magnetometer data, the first evidence of a cushion region forming at Saturn is shown. Only five examples of a sustained cushion are found, revealing this phenomenon to be rare. Four of the cushion regions are identified at dusk and one pre‐noon. It is suggested that greater heating of plasma post‐noon coupled with the expansion of the field through the afternoon sector makes the disc more unstable in this region. These results highlight a key difference between the Saturn and Jupiter systems.
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Journal articleStephenson P, Galand M, Feldman PD, et al., 2021,
Multi-instrument analysis of far-ultraviolet aurora in the southern hemisphere of Comet 67P/Churyumov-Gerasimenko
, Astronomy and Astrophysics: a European journal, Vol: 647, Pages: 1-19, ISSN: 0004-6361Aims. We aim to determine whether dissociative excitation of cometary neutrals by electron impact is the major source of far ultraviolet (FUV) emissions at comet 67P/Churyumov-Gerasimenko in the southern hemisphere at large heliocentric distances, bothduring quiet conditions and impacts of corotating interaction regions observed in the summer of 2016.Methods. We combined multiple datasets from the Rosetta mission through a multi-instrument analysis to complete the first forwardmodelling of FUV emissions in the southern hemisphere of comet 67P and compared modelled brightnesses to observations with theAlice FUV imaging spectrograph. We modelled the brightness of OI1356, OI1304, Lyman-β, CI1657, and CII1335 emissions, whichare associated with the dissociation products of the four major neutral species in the coma: CO2, H2O, CO, and O2. The suprathermalelectron population was probed by the Ion and Electron Sensor of the Rosetta Plasma Consortium (RPC/IES) and the neutral col umn density was constrained by several instruments: the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA), theMicrowave Instrument for the Rosetta Orbiter (MIRO) and the Visual InfraRed Thermal Imaging Spectrometer (VIRTIS).Results. The modelled and observed brightnesses of the FUV emission lines agree closely when viewing nadir and dissociativeexcitation by electron impact is shown to be the dominant source of emissions away from perihelion. The CII1335 emissions areshown to be consistent with the volume mixing ratio of CO derived from ROSINA. When viewing the limb during the impactsof corotating interaction regions, the model reproduces brightnesses of OI1356 and CI1657 well, but resonance scattering in theextended coma may contribute significantly to the observed Lyman-β and OI1304 emissions. The correlation between variationsin the suprathermal electron flux and the observed FUV line brightnesses when viewing the comet’s limb suggests electrons areaccelerated on
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Journal articleGoodrich KA, Bonnell JW, Curry S, et al., 2021,
Evidence of Subproton-Scale Magnetic Holes in the Venusian Magnetosheath
, GEOPHYSICAL RESEARCH LETTERS, Vol: 48, ISSN: 0094-8276- Cite
- Citations: 24
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Journal articleSiddle AG, Mueller-Wodarg ICF, Bruinsma S, et al., 2021,
Density structures in the martian lower thermosphere as inferred by Trace Gas Orbiter accelerometer measurements
, ICARUS, Vol: 357, ISSN: 0019-1035- Author Web Link
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- Citations: 5
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Journal articleNave G, Clear C, 2021,
Reference wavelengths of Si ii, C ii, Fe i, and Ni ii for quasar absorption spectroscopy
, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 502, Pages: 5679-5685, ISSN: 0035-8711 -
Journal articleShebanits O, Hadid L, Cao H, et al., 2021,
The conductive dusty ionosphere of Saturn
<jats:p>&lt;p&gt;Cassini&amp;#8217;s Grand Finale orbits brought us historical first in-situ measurements of Saturn&amp;#8217;s ionosphere, showing that it contains dusty plasma in the equatorial region. We present the Pedersen and Hall conductivities of the top ionosphere (10:50 &amp;#8211; 12:17 Saturn Local Time, 10N &amp;#8211; 20S planetocentric latitude), derived from particle and magnetometer data. We constrain the Pedersen conductivities to be at least 10&lt;sup&gt;-5&lt;/sup&gt; &amp;#8211; 10&lt;sup&gt;-4&lt;/sup&gt; S/m at ionospheric peak, a factor 10-100 higher than estimated previously by remote measurements, while the Hall conductivities are very close to 0 or in fact negative. We show that this is an effect of dusty plasma. Another effect is that ionospheric dynamo region thickness is increased to 300-800 km. Furthermore, our results suggest a temporal variation (decrease) of the plasma densities, mean ion masses and consequently the conductivities over the period of one month.&lt;/p&gt;</jats:p>
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Conference paperStephenson P, Galand M, Deca J, et al., 2021,
Electron cooling at a weakly outgassing comet
<jats:p>&lt;p&gt;The Rosetta spacecraft arrived at comet 67P in August 2014 and then escorted it for 2 years along its orbit. Throughout this escort phase, two plasma instruments (Mutual Impedance Probe, MIP; and Langmuir Probe, LAP) measured a population of cold electrons (&lt; 1 eV) within the coma of 67P (Engelhardt et al., 2018; Wattieaux et al, 2020; Gilet et al., 2020). These cold electrons are understood to be formed by cooling warm electrons through collisions with the neutral gas. The warm electrons are primarily newly-born and produced at roughly 10eV within the coma through ionisation. While it was no surprise that cold electrons would form near perihelion given the high density of the neutral coma, the persistence of the cold electrons up to a heliocentric distance of 3.8 au was highly unexpected. With the low outgassing rates observed at such large heliocentric distances (Q &lt; 10&lt;sup&gt;26&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;), there should not be enough neutral molecules to cool the warm electrons efficiently before they ballistically escape the coma.&lt;/p&gt;&lt;p&gt;We use a collisional test particle model to examine the formation of the cold electron population at a weakly outgassing comet. The electrons are subject to stochastic collisions with the neutral coma which can either scatter or cool the electrons. Multiple electron neutral collision processes are included such that the electrons can undergo elastic scattering as well as collisions inducing excitation and ionisation of the neutral species. The inputted electric and magnetic fields, which act on the test particles, are taken from a 3D fully-kinetic, collisionless Particle-in-Cell (PiC) model of the solar wind and cometary ionosphere (Deca et al., 2017; 2019), with the same neutral coma as used in our model. We use a pure water coma with spherical sym
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Conference paperBaran J, Rothkaehl H, Andre N, et al., 2021,
The challenges of&#160; the Dust-Field-Plasma&#160; (DFP) instrument onboard ESA &#160;Comet Interceptor mission&#160;
<jats:p>&lt;p&gt;The&amp;#160;flyby of a dynamically new comet by ESA-F1 Comet Interceptor spacecraft offers unique multi-point&amp;#160;opportunities for studying the comet's dusty and ionised cometary &amp;#160;environment in ways that were not possible with previous missions, including Rosetta. As Comet Interceptor is an F-class mission, the payload is limited in terms of mass, power, and heritage. Most in situ science sensors therefore have been tightly integrated into a single Dust-Field-Plasma (DFP) instrument on the main spacecraft A and on the ESA sub-spacecraft B2, while there is&amp;#160;a Plasma Package suite on the&amp;#160;JAXA second sub-spacecraft B1. The advantage of tight integration is an important reduction of mass, power, and especially complexity, by keeping the electrical and data interfaces of the sensors internal to the DFP instrument.&lt;/p&gt;&lt;p&gt;The full diagnostics located on the board of the 3 spacecrafts will allow&amp;#160; to modeling the comet environment and described the complex physical processes around the comet and on their surface including also the&amp;#160; description of wave particle&amp;#160; interaction in dusty cometary plasma.&amp;#160;&lt;/p&gt;&lt;p&gt;The full set of DFP instrument&amp;#160;on &amp;#160;board the Comet Interceptor &amp;#160;spacecraft will allow&amp;#160;to model &amp;#160;the comet plasma&amp;#160;environment and&amp;#160;its interaction with the solar wind.&amp;#160;It will also allow to&amp;#160;describe&amp;#160;the complex physical processes taking place including wave particle&amp;#160;&amp;#160;interaction in dusty cometary plasma .&amp;#160;&lt;/p&gt;&lt;p&gt;On spacecraft A, DFP consists of a magne
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Journal articleKasoar M, Hamilton D, Dalmonech D, et al., 2021,
Improved estimates of future fire emissions under CMIP6 scenarios and implications for aerosol radiative forcing
<jats:p>&lt;p&gt;The CMIP6 Shared Socioeconomic Pathway (SSP) scenarios include projections of future changes in anthropogenic biomass-burning.&amp;#160; Globally, they assume a decrease in total fire emissions over the next century under all scenarios.&amp;#160; However, fire regimes and emissions are expected to additionally change with future climate, and the methodology used to project fire emissions in the SSP scenarios is opaque.&lt;/p&gt;&lt;p&gt;We aim to provide a more traceable estimate of future fire emissions under CMIP6 scenarios and evaluate the impacts for aerosol radiative forcing. &amp;#160;We utilise interactive wildfire emissions from four independent land-surface models (CLM5, JSBACH3.2, LPJ-GUESS, and ISBA-CTRIP) used within CMIP6 ESMs, and two different machine-learning methods (a random forest, and a generalised additive model) trained on historical data, to predict year 2100 biomass-burning aerosol emissions consistent with the CMIP6-modelled climate for three different scenarios: SSP126, SSP370, and SSP585.&amp;#160; This multi-method approach provides future fire emissions integrating information from observations, projections of climate, socioeconomic parameters and changes in vegetation distribution and fuel loads.&lt;/p&gt;&lt;p&gt;Our analysis shows a robust increase in fire emissions for large areas of the extra-tropics until the end of this century for all methods.&amp;#160; Although this pattern was present to an extent in the original SSP projections, both the interactive fire models and machine-learning methods predict substantially higher increases in extra-tropical emissions in 2100 than the corresponding SSP datasets.&amp;#160; Within the tropics the signal is mixed. Increases in emissions are largely driven by the temperature changes, while in some tropical areas reductions in fire emissions are
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Journal articleMillington J, Perkins O, Kasoar M, et al., 2021,
Advancing representation of anthropogenic fire in dynamic global vegetation models
<jats:p>&lt;div&gt;&lt;p&gt;It is now commonly-understood that improved understanding of global fire regimes demands better representation of anthropogenic fire in dynamic global vegetation models (DGVMs). However, currently there is no clear agreement on how human activity should be incorporated into fire-enabled DGVMs and existing models exhibit large differences in the sensitivities of socio-economic variables. Furthermore, existing approaches are limited to empirical statistical relations between fire regime variables and globally available socio-economic indicators such as population density or GDP. Although there has been some limited representation in global models of the contrasting ways in which different classes of actors use or manage fires, we argue that fruitful progress in advancing representation of anthropogenic fire in DGVMs will come by building on agent-based modelling approaches. Here, we report on our progress developing a global agent-based representation of anthropogenic fire and its coupling with the JULES-INFERNO fire-enabled DGVM.&amp;#160;&amp;#160;&lt;/p&gt;&lt;/div&gt;&lt;div&gt;&lt;p&gt;Our modelling of anthropogenic fire adopts an approach that classifies &amp;#8216;agent functional types&amp;#8217; (AFTs) to represent human fire activity based on land use/cover and Stephen Pyne&amp;#8217;s fire development stages. For example, the &amp;#8216;swidden&amp;#8217; AFT represents shifting cultivation farmers managing cropland and secondary vegetation in a pre-industrial development setting. This approach is based on the assumption that anthropogenic fire use and management is primarily a function of land use but influenced by socio-economic context, leading different AFTs to produce qualitatively distinct fire regimes. The literature empirically supports this assumption, however data
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Journal articleWells C, Voulgarakis A, 2021,
The local and remote atmospheric impacts of Africa&#8217;s 21st century aerosol emission trajectory
<jats:p>&lt;p&gt;Aerosols are a major climate forcer, but their historical effect has the largest uncertainty of any forcing; their mechanisms and impacts are not well understood. Due to their short lifetime, aerosols have large impacts near their emission region, but they also have effects on the climate in remote locations. In recent years, studies have investigated the influences of regional aerosols on global and regional climate, and the mechanisms that lead to remote responses to their inhomogeneous forcing. Using the Shared Socioeconomic Pathway scenarios (SSPs), transient future experiments were performed in UKESM1, testing the effect of African emissions following the SSP3-RCP7.0 scenario as the rest of the world follows SSP1-RCP1.9, relative to a global SSP1-RCP1.9 control. SSP3 sees higher direct anthropogenic aerosol emissions, but lower biomass burning emissions, over Africa. Experiments were performed changing each of these sets of emissions, and both. A further set of experiments additionally accounted for changing future CO&lt;sub&gt;2&lt;/sub&gt; concentrations, to investigate the impact of CO&lt;sub&gt;2&lt;/sub&gt; on the responses to aerosol perturbations. Impacts on radiation fluxes, temperature, circulation and precipitation are investigated, both over the emission region (Africa), where microphysical effects dominate, and remotely, where dynamical influences become more relevant.&amp;#160;&lt;/p&gt;</jats:p>
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Journal articleMansfield L, Nowack P, Voulgarakis A, 2021,
Predicting climate model response to changing emissions
<jats:p>&lt;p&gt;In order to make predictions on how the climate would respond to changes in global and regional emissions, we typically run simulations on Global Climate Models (GCMs) with perturbed emissions or concentration fields. These simulations are highly expensive and often require the availability of high-performance computers. Machine Learning (ML) can provide an alternative approach to estimating climate response to various emissions quickly and cheaply.&amp;#160;&lt;/p&gt;&lt;p&gt;We will present a Gaussian process emulator capable of predicting the global map of temperature response to different types of emissions (both greenhouse gases and aerosol pollutants), trained on a carefully designed set of simulations from a GCM. This particular work involves making short-term predictions on 5 year timescales but can be linked to an emulator from previous work that predicts on decadal timescales. We can also examine uncertainties associated with predictions to find out where where the method could benefit from increased training data. This is a particularly useful asset when constructing emulators for complex models, such as GCMs, where obtaining training runs is costly.&amp;#160;&lt;/p&gt;</jats:p>
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Journal articleStawarz J, Matteini L, Parashar T, et al., 2021,
Comparative Analysis of the Various Generalized Ohm's Law Terms in Magnetosheath Turbulence as Observed by Magnetospheric Multiscale
<jats:p>&lt;p&gt;&lt;span&gt;Electric fields (&lt;strong&gt;E&lt;/strong&gt;) play a fundamental role in facilitating the exchange of energy between the electromagnetic fields and the changed particles within a plasma. &lt;/span&gt;Decomposing &lt;strong&gt;E&lt;/strong&gt; into the contributions from the different terms in generalized Ohm's law, therefore, provides key insight into both the nonlinear and dissipative dynamics across the full range of scales within a plasma. Using the unique, high&amp;#8208;resolution, multi&amp;#8208;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 electric field&lt;strong&gt; &lt;/strong&gt;spectrum are examined observationally for the first time. The magnetohydrodynamic, Hall, and electron pressure terms are the dominant contributions to &lt;strong&gt;E&lt;/strong&gt; over the accessible length scales, which extend to scales smaller than the electron gyroradius at the greatest extent, with the Hall and electron pressure terms dominating at sub&amp;#8208;ion scales. The strength of the non&amp;#8208;ideal electron pressure contribution is stronger than expected from linear kinetic Alfv&amp;#233;n waves and a partial anti&amp;#8208;alignment with the Hall electric field is present, linked to the relative importance of electron diamagnetic currents within the turbulence. The relative contributions of linear and nonlinear electric fields scale with the turbulent fluctuation amplitude, with nonlinear contributions playing the dominant role in shaping &lt;strong&am
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Journal articleWoolley T, Matteini L, Horbury TS, et al., 2021,
Characterisation and comparison of slow coronal hole wind intervals at 0.13au
<jats:p>&lt;p&gt;The slow solar wind is thought to consist of a component originating close to the Heliospheric Current Sheet (HCS) in the streamer belt and a component from over-expanded coronal hole boundaries. In order to understand the roles of these contributions with different origin, it is important to separate and characterise them. By exploiting the fact that Parker Solar Probe&amp;#8217;s fourth and fifth orbits were the same and the solar conditions were similar, we identify intervals of slow polar coronal hole wind sampled at approximately the same heliocentric distance and latitude. Here, solar wind properties are compared, highlighting typical conditions of the slow coronal hole wind closer to the Sun than ever before. We explore different properties of the plasma, including composition, spectra and microphysics, and discuss possible origins for the features that are observed.&lt;/p&gt;</jats:p>
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Journal articleGood S, Kilpua E, Ala-Lahti M, et al., 2021,
Cross helicity of magnetic clouds observed by Parker Solar Probe
<jats:p>&lt;p&gt;Magnetic clouds are large-scale transient structures in the solar wind with low plasma &lt;em&gt;&amp;#946;&lt;/em&gt;, low-amplitude magnetic field fluctuations, and twisted field lines with both ends often connected to the Sun. We analyse the normalised cross helicity, &lt;em&gt;&amp;#963;&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt;, and residual energy, &lt;em&gt;&amp;#963;&lt;/em&gt;&lt;sub&gt;r&lt;/sub&gt;, in magnetic clouds observed by Parker Solar Probe (PSP). In the November 2018 cloud observed at 0.25 au, a low value of &lt;em&gt;&amp;#963;&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt; was present in the cloud core, indicating that wave power parallel and anti-parallel to the mean field was approximately balanced, while the cloud&amp;#8217;s outer layers displayed larger amplitude Alfv&amp;#233;nic fluctuations with high &lt;em&gt;&amp;#963;&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt; values and &lt;em&gt;&amp;#963;&lt;/em&gt;&lt;sub&gt;r&lt;/sub&gt; ~ 0. These properties are compared and contrasted to those found in clouds observed by PSP at larger heliocentric distances. We suggest that low &lt;em&gt;&amp;#963;&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt; is likely a common feature of magnetic clouds given their typically closed field structure, in contrast to the generally higher &lt;em&gt;&amp;#963;&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt; found on the open field lines of the solar wind.&lt;/p&
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