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Journal articleArcher M, Waters C, Dewan S, et al., 2022,
GC Insights: Space sector careers resources in the UK need a greater diversity of roles
, Geoscience Communication, Vol: 5, Pages: 119-123, ISSN: 2569-7110Educational research highlights that improved careers education is needed to increase participation in science, technology, engineering, and mathematics (STEM). Current UK careers resources concerning the space sector, however, are found to perhaps not best reflect the diversity of roles present and may in fact perpetuate misconceptions about the usefulness of science. We, therefore, compile a more diverse set of space-related jobs, which will be used in the development of a new space careers resource.
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Journal articleBrown ZL, Medvedev AS, Starichenko ED, et al., 2022,
Evidence for Gravity Waves in the Thermosphere of Saturn and Implications for Global Circulation
, GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276- Author Web Link
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- Citations: 4
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Journal articleSalvi P, Ceppi P, Gregory JM, 2022,
Interpreting differences in radiative feedbacks from aerosols versus greenhouse gases
, Geophysical Research Letters, Vol: 49, Pages: 1-9, ISSN: 0094-8276Experiments with seven Coupled Model Intercomparison Project phase 6 models were used to assess the climate feedback parameter for net historical, historical greenhouse gas (GHG) and anthropogenic aerosol forcings. The net radiative feedback is found to be more amplifying (higher effective climate sensitivity) for aerosol than GHG forcing, and hence also less amplifying for net historical (GHG + aerosol) than GHG only. We demonstrate that this difference is consistent with their different latitudinal distributions. Historical aerosol forcing is most pronounced in northern extratropics, where the boundary layer is decoupled from the free troposphere, so the consequent temperature change is confined to low altitude and causes low-level cloud changes. This is caused by change in stability, which also affects upper-tropospheric clear-sky emission, affecting both shortwave and longwave radiative feedbacks. This response is a feature of extratropical forcing generally, regardless of its sign or hemisphere.
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Journal articleHall RJ, Mitchell DM, Seviour WJM, et al., 2022,
How Well Are Sudden Stratospheric Warming Surface Impacts Captured in CMIP6 Climate Models?
, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, Vol: 127, ISSN: 2169-897X- Author Web Link
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- Citations: 3
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Journal articleWarwick L, Brindley H, Di Roma A, et al., 2022,
Retrieval of tropospheric water vapour from airborne far-infrared measurements: a case study
, Journal of Geophysical Research: Atmospheres, Vol: 127, ISSN: 2169-897XWe describe studies undertaken in support of the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission, ESA’s ninth Earth Explorer, designed to investigate whether airborne observations of far-infrared radiances can provide beneficial information on mid and upper tropospheric water vapour concentrations.Initially we perform a joint temperature and water vapour retrieval and show that the water vapour retrieval exploiting far-infrared measurements from the Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) shows improvement over the a-priori Unified Model global forecast when compared to in situ dropsonde measurements. For this case the improvement is particularly noticeable in the mid-upper troposphere. Equivalent retrievals using mid-infrared radiances measured by the Airborne Research Interferometer Evaluation System (ARIES) show much reduced performance, with the degrees of freedom for signal (DFS), reduced by a factor of almost 2. Further sensitivity studies show that this advantage is decreased, but still present when the spectral resolution of the TAFTS measurements is reduced to match that of ARIES.The beneficial role of the far infrared for this case is further confirmed by performing water vapour only retrievals using ARIES and TAFTS individually, and then in combination. We find that the combined retrieval has a DFS value of 6.7 for water vapour, marginally larger than that obtained for the TAFTS retrieval and almost twice as large as that obtained for ARIES.These results provide observational support of theoretical studies highlighting the potential improvement that far-infrared observations could bring for the retrieval of tropospheric water vapour.
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Journal articleDimmock AP, Khotyaintsev YV, Lalti A, et al., 2022,
Analysis of multiscale structures at the quasi-perpendicular Venus bow shock Results from Solar Orbiter's first Venus flyby
, ASTRONOMY & ASTROPHYSICS, Vol: 660, ISSN: 0004-6361- Author Web Link
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- Citations: 3
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Journal articleBessho N, Chen L-J, Stawarz J, et al., 2022,
Strong reconnection electric fields in shock-driven turbulence
, Physics of Plasmas, Vol: 29, Pages: 1-23, ISSN: 1070-664XTurbulent magnetic reconnection in a quasi-parallel shock under parameters relevant to the Earth's bow shock is investigated by means of a two-dimensional particle-in-cell simulation. The addressed aspects include the reconnection electric field, the reconnection rate, and the electron and the ion outflow speeds. In the shock transition region, many current sheets are generated in shock-driven turbulence, and electron-only reconnection and reconnection where both ions and electrons are involved can occur in those current sheets. The electron outflow speed in electron-only reconnection shows a positive correlation with the theoretical speed, which is close to the local electron Alfvén speed, and a strong convection electric field is generated by the large electron outflow. As a result, the reconnection electric field becomes much larger than those in the standard magnetopause or magnetotail reconnection. In shock-driven reconnection that involves ion dynamics, both electron outflows and ion outflows can reach of the order of 10 times the Alfvén speed in the X-line rest frame, leading to a reconnection electric field the same order as that in electron-only reconnection. An electron-only reconnection event observed by the magnetospheric multiscale mission downstream of a quasi-parallel shock is qualitatively similar to those in the simulation and shows that the outflow speed reaches approximately half the local electron Alfvén speed, supporting the simulation prediction.
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Journal articleEggington J, Desai R, Mejnertsen L, et al., 2022,
Time-varying magnetopause reconnection during sudden commencement: global MHD simulations
, Journal of Geophysical Research: Space Physics, Vol: 127, ISSN: 2169-9380In response to a solar wind dynamic pressure enhancement, the compression of the magnetosphere generates strong ionospheric signatures and a sharp variation in the ground magnetic field, termed sudden commencement (SC). Whilst such compressions have also been associated with a contraction of the ionospheric polar cap due to the triggering of reconnection in the magnetotail, the effect of any changes in dayside reconnection is less clear and is a key component in fully understanding the system response. In this study we explore the time-dependent nature of dayside coupling during SC by performing global simulations using the Gorgon MHD code, and impact the magnetosphere with a series of interplanetary shocks with different parameters. We identify the location and evolu tion of the reconnection region in each case as the shock propagates through the magnetosphere, finding strong enhancement in the dayside reconnection rate and prompt expansion of the dayside polar cap prior to the eventual triggering of tail reconnection. This effect pervades for a variety of IMF orientations, and the reconnection rate is most enhanced for events with higher dynamic pressure. We explain this by repeating the simulations with a large explicit resistivity, showing that compression of the magnetosheath plasma near the propagating shock front allows for reconnection of much greater intensity and at different locations on the dayside magnetopause than during typical solar wind conditions. The results indicate that the dynamic behaviour of dayside coupling may render steady models of reconnection inaccurate during the onset of a severe space weather event.
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Journal articleRovithakis A, Grillakis MG, Seiradakis KD, et al., 2022,
Future climate change impact on wildfire danger over the Mediterranean: the case of Greece
, Environmental Research Letters, Vol: 17, ISSN: 1748-9326Recent studies have shown that temperature and precipitation in the Mediterranean are expected to change, contributing to longer and more intense summer droughts that even extend out of season. In connection to this, the frequency of forest fire occurrence and intensity will likely increase. In the present study, the changes in future fire danger conditions are assessed for the different regions of Greece using the Canadian fire weather index (FWI). Gridded future climate output as estimated from three regional climate models from the Coordinated Regional Downscaling Experiment are utilized. We use three representative concentration pathways (RCPs) consisting of an optimistic emissions scenario where emissions peak and decline beyond 2020 (RCP2.6), a middle-of-the-road scenario (RCP4.5) and a pessimistic scenario, in terms of mitigation where emissions continue to rise throughout the century (RCP8.5). Based on established critical fire FWI threshold values for Greece, the future change in days with critical fire danger were calculated for different areas of Greece domains. The results show that fire danger is expected to progressively increase in the future especially in the high-end climate change scenario with southern and eastern regions of Greece expected to have up to 40 additional days of high fire danger relative to the late 20th century, on average. Crete, the Aegean Islands, the Attica region, as well as parts of Peloponnese are predicted to experience a stronger increase in fire danger.
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Journal articleZhao L-L, Zank GP, Telloni D, et al., 2022,
The Turbulent Properties of the Sub-Alfvenic Solar Wind Measured by the Parker Solar Probe
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 928, ISSN: 2041-8205- Author Web Link
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- Citations: 14
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Journal articleLotekar AB, Vasko IY, Phan T, et al., 2022,
Kinetic-scale Current Sheets in Near-Sun Solar Wind: Properties, Scale-dependent Features and Reconnection Onset
, ASTROPHYSICAL JOURNAL, Vol: 929, ISSN: 0004-637X- Author Web Link
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- Citations: 5
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Journal articleGrillakis M, Voulgarakis A, Rovithakis A, et al., 2022,
Climate drivers of global wildfire burned area
, Environmental Research Letters, Vol: 17, Pages: 1-10, ISSN: 1748-9326Wildfire is an integral part of the Earth system, but at the same time it can pose serious threats to human society and to certain types of terrestrial ecosystems. Meteorological conditions are a key driver of wildfire activity and extent, which led to the emergence of the use of fire danger indices that depend solely on weather conditions. The Canadian Fire Weather Index (FWI) is a widely used fire danger index of this kind. Here, we evaluate how well the FWI, its components, and the climate variables from which it is derived, correlate with observation-based burned area (BA) for a variety of world regions. We use a novel technique, according to which monthly BA are grouped by size for each Global Fire Emissions Database (GFED) pyrographic region. We find strong correlations of BA anomalies with the FWI anomalies, as well as with the underlying deviations from their climatologies for the four climate variables from which FWI is estimated, namely, temperature, relative humidity, precipitation, and wind. We quantify the relative sensitivity of the observed BA to each of the four climate variables, finding that this relationship strongly depends on the pyrographic region and land type. Our results indicate that the BA anomalies strongly correlate with FWI anomalies at a GFED region scale, compared to the strength of the correlation with individual climate variables. Additionally, among the individual climate variables that comprise the FWI, relative humidity and temperature are the most influential factors that affect the observed BA. Our results support the use of the composite fire danger index FWI, as well as its sub-indices, the Build-Up Index (BUI) and the Initial Spread Index (ISI), comparing to single climate variables, since they are found to correlate better with the observed forest or non-forest BA, for the most regions across the globe.
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Journal articleStephenson P, Galand M, Deca J, et al., 2022,
A collisional test particle model of electrons at a comet
, Monthly Notices of the Royal Astronomical Society, Vol: 511, Pages: 4090-4108, ISSN: 0035-8711We have developed the first 3D collisional model of electrons at a comet, which we use to examine the impact of electron-neutral collisions in the weakly outgassing regime. The test-particle Monte Carlo model uses electric and magnetic fields from a fully kinetic Particle-in-Cell (PiC) model as an input. In our model, electrons originate from the solar wind or from ionization of the neutral coma, either by electron impact or absorption of an extreme ultraviolet photon. All relevant electron-neutral collision processes are included in the model including elastic scattering, excitation, and ionization. Trajectories of electrons are validated against analytically known drifts and the stochastic energy degradation used in the model is compared to the continuous slowing down approximation. Macroscopic properties of the solar wind and cometary electron populations, such as density and temperature, are validated with simple known cases and via comparison with the collisionless PiC model. We demonstrate that electrons are trapped close to the nucleus by the ambipolar electric field, causing an increase in the efficiency of electron-neutral collisions. Even at a low-outgassing rate (Q = 1026 s−1), electron-neutral collisions are shown to cause significant cooling in the coma. The model also provides a multistep numerical framework that is used to assess the influence of the electron-to-ion mass ratio, enabling access to electron dynamics with a physical electron mass.
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Journal articlede Wit TD, Krasnoselskikh VV, Agapitov O, et al., 2022,
First Results From the SCM Search-Coil Magnetometer on Parker Solar Probe
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380- Author Web Link
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- Citations: 9
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Journal articleKoller F, Temmer M, Preisser L, et al., 2022,
Magnetosheath jet occurrence rate in relation to CMEs and SIRs
, Journal of Geophysical Research: Space Physics, Vol: 127, ISSN: 2169-9380Magnetosheath jets constitute a significant coupling effect between the solar wind (SW) and the magnetosphere of the Earth. In order to investigate the effects and forecasting of these jets, we present the first-ever statistical study of the jet production during large-scale SW structures like coronal mass ejections (CMEs), stream interaction regions (SIRs) and high speed streams (HSSs). Magnetosheath data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft between January 2008 and December 2020 serve as measurement source for jet detection. Two different jet definitions were used to rule out statistical biases induced by our jet detection method. For the CME and SIR + HSS lists, we used lists provided by literature and expanded on incomplete lists using OMNI data to cover the time range of May 1996 to December 2020. We find that the number and total time of observed jets decrease when CME-sheaths hit the Earth. The number of jets is lower throughout the passing of the CME-magnetic ejecta (ME) and recovers quickly afterward. On the other hand, the number of jets increases during SIR and HSS phases. We discuss a few possibilities to explain these statistical results.
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Journal articleMartinovic MM, Dordevic AR, Klein KG, et al., 2022,
Plasma Parameters From Quasi-Thermal Noise Observed by Parker Solar Probe: A New Model for the Antenna Response
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380- Author Web Link
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- Citations: 2
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Journal articleMyhre G, Samset B, Forster PM, et al., 2022,
Scientific data from precipitation driver response model intercomparison project
, Scientific Data, Vol: 9, Pages: 123-123, ISSN: 2052-4463This data descriptor reports the main scientific values from General Circulation Models (GCMs) in the Precipitation Driver and Response Model Intercomparison Project (PDRMIP). The purpose of the GCM simulations has been to enhance the scientific understanding of how changes in greenhouse gases, aerosols, and incoming solar radiation perturb the Earth's radiation balance and its climate response in terms of changes in temperature and precipitation. Here we provide global and annual mean results for a large set of coupled atmospheric-ocean GCM simulations and a description of how to easily extract files from the dataset. The simulations consist of single idealized perturbations to the climate system and have been shown to achieve important insight in complex climate simulations. We therefore expect this data set to be valuable and highly used to understand simulations from complex GCMs and Earth System Models for various phases of the Coupled Model Intercomparison Project.
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Conference paperDipu S, Schwarz M, Ekman AML, et al., 2022,
Exploring satellite-derived relationships between cloud droplet number concentration and liquid water path using large-domain large-eddy simulation
<jats:p>&lt;p&gt;Important aspects of the adjustments to aerosol-cloud interactions can be examined using the relationship between cloud droplet number concentration (N&lt;sub&gt;d&lt;/sub&gt;) and liquid water path (LWP). Specifically, this relation can constrain the role of aerosols in leading to thicker or thinner clouds in response to adjustment mechanisms. This study investigates the satellite retrieved relationship between N&lt;sub&gt;d&lt;/sub&gt; and LWP for a selected case of mid-latitude continental clouds using high-resolution Large-eddy simulations (LES) over a large domain in weather prediction mode. Since the satellite retrieval uses the adiabatic assumption to derive the N&lt;sub&gt;d&lt;/sub&gt; (N&lt;sub&gt;Ad&lt;/sub&gt;), we have also considered N&lt;sub&gt;Ad&lt;/sub&gt; from the LES model for comparison. The joint histogram analysis shows that the N&lt;sub&gt;Ad&lt;/sub&gt;-LWP relationship in the LES model and the satellite is in approximate agreement. In both cases, the peak conditional probability (CP) is confined to lower N&lt;sub&gt;Ad&lt;/sub&gt; and LWP, and the corresponding mean LWP shows a weak relation with N&lt;sub&gt;Ad&lt;/sub&gt;. In contrast, at higher N&lt;sub&gt;Ad&lt;/sub&gt; (&gt; 50 cm&lt;sup&gt;&amp;#8722;3&lt;/sup&gt; ), the CP shows a larger spread; consequently, the mean LWP increases non-monotonically with increasing N&lt;sub&gt;Ad&lt;/sub&gt; in both cases. However, the N&lt;sub&gt;Ad&lt;/sub&gt;-LWP relation lacks, in particular, the negative sensitivity at higher N&lt;sub&gt;Ad&l
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Conference paperSourdeval O, Gryspeerdt E, Krämer M, et al., 2022,
Assessment of ice clouds - aerosol interactions in global satellite observations
<jats:p>&lt;p&gt;Interactions between aerosols and clouds, as well as their radiative consequences, have been a long-standing problem to understand cloud physics as well as anthropogenic impacts on climate. Satellite-based investigations of the direct and indirect impact of aerosols on liquid clouds have led to significant progress in the understanding during the last decade. This is partly due to the emergence of adapted cloud properties provided by satellites, such as the droplet number concentration. Ice clouds have suffered from such adapted quantity for much longer, but solutions have recently been appearing.&lt;/p&gt;&lt;p&gt;This study investigates aerosol - ice clouds interactions using ice crystal number concentration (Ni) profiles from a lidar-radar dataset (DARDAR-Nice), used cojointly with with collocated aerosol information from the Copernicus Atmospheric Monitoring Service (CAMS) reanalyses. A multitude of cloud regimes, subdivided into seasonal and regional bins, are considered in order to disentangle meteorological effects from the aci signature. First results of joint-histograms between Ni and the aerosol mass show an overall positive sensitivity of Ni to the aerosols load. This response is particularly strong towards to cloud-top and flattens towards cloud-base, consistently with expectations for homogeneous nucleation processes. The response of the ice water content, in terms of adjustment to the initial aerosol perturbation as also quantified.&lt;/p&gt;</jats:p>
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Journal articleWang S, Toumi R, 2022,
More tropical cyclones are striking coasts with major intensities at landfall
, Scientific Reports, Vol: 12, ISSN: 2045-2322In this study we show that the number of annual global tropical cyclone (TC) landfalls with major landfall intensity (LI≥50 m s-1) has nearly doubled from 1982 to 2020. The lifetime maximum intensity (LMI) of global major landfalling TCs has been increasing by 0.8 m s-1 per decade (p<0.05), but this significance of intensity change disappears at landfall (0.3 m s-1 per decade, p=0.69). The lack of a significant LI trend is caused by the much larger variance of LI than that of LMI in all basins and explains why a significant count change of TCs with major intensity at landfall has only now emerged. Basin-wide TC trends of intensity and spatial distribution have been reported, but this long-term major TC landfall count change may be the most socio-economic significant.
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Conference paperGryspeerdt E, Louro Coelho M, Smith T, et al., 2022,
Measuring cloud sensitivity to aerosols at a global scale using isolated aerosol sources
<jats:p>&lt;p&gt;The sensitivity of clouds to anthropogenic aerosol perturbations remains one of the largest uncertainties in the human forcing of the climate system. A key difficulty is in isolating the impact of aerosols from large-scale covariability of aerosol and cloud properties. Natural experiments, where aerosol is produced independently of the cloud and meteorological properties, provide a pathway to address this issue. These aerosol sources often modify cloud properties, leaving linear cloud features known as shiptracks (when formed by a ship) or pollution tracks (more generally).&lt;/p&gt;&lt;p&gt;In this work, we use a database of point sources of aerosol over both land and ocean to identify clouds that are sensitive to aerosol and to measure their response. Using a neural network to identify when a point source is modifying the cloud, we are able to measure the sensitivity of individual clouds to aerosol at a global scale, looking at over 400 million cases.&lt;/p&gt;&lt;p&gt;We find the probability of track formation is strongly dependent on the background cloud and meteorological state, similar to previous regional studies. With our global database, we identify regions that are strongly susceptible to aerosol perturbations, even where aerosol sources are rare. We find that there are several regions that are highly susceptible to aerosol, but that have been previously overlooked due to a low frequency of pollution tracks. &amp;#160; &amp;#160;&lt;/p&gt;</jats:p>
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Journal articleArcher M, Waters C, Dewan S, et al., 2022,
Developing a new space sector careers resource based on educational research recommendations
<jats:p>&lt;p&gt;Educational research shows participation issues across Science Technology Engineering and Mathematics (STEM) are due to whether students see these fields and their potential career opportunities as for &amp;#8220;people like me&amp;#8221;. These perceptions form early and remain relatively stable with age, which has led to recommendations for increased provision and quality of careers education/engagement at both primary and secondary levels. Space-related roles should be rife for inclusion in careers education resources. However, we find that current UK careers resources concerning the space sector do not perhaps best reflect the diversity of roles present and may in fact perpetuate misconceptions about the usefulness of science. We present the development process of a new space careers resource, detailing how we have attempted to improve the diversity of space-related careers highlighted as well as addressing the key issues and recommendations raised by recent educational research.&lt;/p&gt;</jats:p>
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Conference paperGoren T, Feingold G, Gryspeerdt E, et al., 2022,
Exploring the Effect of Aerosol on Marine Cloud Cover Using a Counterfactual Approach
<jats:p>&lt;p&gt;Aerosol&amp;#8211;cloud interactions in marine stratocumulus clouds (Sc) are among the most challenging frontiers in cloud&amp;#8211;climate research.&amp;#160;In particular, the cloud cover susceptibility to droplet concentration remained under-represented in the literature.&amp;#160;We developed methodologies to estimate what&amp;#160;would have been the cloud cover and&amp;#160;the associated&amp;#160;radiative&amp;#160;&lt;span&gt;effect&lt;/span&gt; of currently observed Sc, but in a hypothetical cleaner world. The first methodology uses a realistic Lagrangian large eddy simulation coupled with satellite observations and provides a process-oriented analysis. The other uses a &lt;span&gt;simple&lt;/span&gt; model and provides a global estimate of the radiative impact. We found that overcast Sc decks would have broken up sooner had they not been influenced by anthropogenic aerosol, thereby causing a significant effective radiative forcing.&lt;/p&gt;</jats:p>
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Journal articleSoljento J, Good S, Osmane A, et al., 2022,
Turbulence modified by velocity shear in coronal mass ejection sheaths
<jats:p>&lt;p&gt;Fast coronal mass ejections (CMEs) drive shock waves ahead of them. The turbulent sheath region between the shock and the CME itself contains magnetic field and velocity fluctuations on a broad spectrum of frequencies. In this work we aim to characterise the direction and source of solar wind fluctuations at MHD fluid scales in CME-driven sheaths near Earth. One possible source for these fluctuations is velocity shear, which are common occurrences in CME-driven sheaths. Here we first identify velocity shear as it occurs and then relate that to signatures of new fluctuations being created locally in the sheath. Turbulence parameters such as cross helicity, residual energy, Elsasser ratio, and Alfv&amp;#233;n ratio are calculated, and they are correlated against large-scale signatures of velocity shear. Findings indicate a clear association between velocity shear and locally generated fluctuations, as well as a balance in the directionality of these new fluctuations, i.e., they tend to propagate equally towards and away from the Sun. In contrast, most solar wind is typically dominated by anti-sunward fluctuations.&lt;/p&gt;</jats:p>
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Journal articleGood S, Hatakka L, Ala-Lahti M, et al., 2022,
Cross helicity of interplanetary coronal mass ejections
<jats:p>&lt;p&gt;Like the solar wind in general, interplanetary coronal mass ejections (ICMEs) display magnetic field and velocity fluctuations across a wide range of scales. These fluctuations may be interpreted as Alfv&amp;#233;nic wave packets propagating parallel or anti-parallel to the local magnetic field direction, with cross helicity, &amp;#963;&lt;sub&gt;c&lt;/sub&gt;, quantifying the difference in power between the counter-propagating fluxes. We have determined &amp;#963;&lt;sub&gt;c&lt;/sub&gt; at inertial range frequencies in a large sample of ICME flux ropes and sheaths observed by the Wind spacecraft at 1 au. The mean &amp;#963;&lt;sub&gt;c&lt;/sub&gt; value was low for both the flux ropes and sheaths, with the balance tipped towards the positive, anti-sunward direction. The low values indicate that Alfv&amp;#233;nic fluxes are more balanced in ICMEs than in the solar wind at 1 au, where &amp;#963;&lt;sub&gt;c&lt;/sub&gt; tends to be larger and anti-sunward fluctuations show a greater predominance. Superposed epoch profiles show &amp;#963;&lt;sub&gt;c&lt;/sub&gt; falling sharply in the upstream sheath and being typically close to balance inside the flux rope near the leading edge. More imbalanced, solar wind-like &amp;#963;&lt;sub&gt;c&lt;/sub&gt; values are found towards the trailing edge and further from the rope axis. The presence or absence of an upstream shock also has a significant effect on &amp;#963;&lt;sub&gt;c&lt;/sub&gt;. Coronal and interplanetary origins of low &amp;#963;&lt;sub&gt;c&lt;/sub&gt; in ICMEs are discussed.&lt;/p&gt;</jats:p>
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Journal articleFranci L, Papini E, Micera A, et al., 2022,
Fully kinetic simulations of the near-Sun solar wind plasma: turbulence, reconnection, and particle heating
<jats:p>&lt;p&gt;We model the development of plasma turbulence in the near-Sun solar wind with high-resolution fully-kinetic particle-in-cell (PIC) simulations, initialised with plasma conditions measured by Parker Solar Probe during its first solar encounter (ion and electron plasma beta &amp;#8804; 1 and a large amplitude of the turbulent fluctuations). The power spectra of the plasma and electromagnetic fluctuations are characterized by multiple power-law intervals, with a transition and a considerable steepening in correspondence of the electron scales. In the same range of scales, the kurtosis of the magnetic fluctuations is observed to further increase, hinting at a higher level of intermittency. We observe a number of electron-only reconnection events, which are responsible for an increase of the electron temperature in the direction parallel to the ambient field. The total electron temperature, however, exhibits only a small increase due to the cooling of electrons in the perpendicular direction, leading to a strong temperature anisotropy. We also analyse the power spectra of the different terms of the electric field in the generalised Ohm&amp;#8217;s law, their linear and nonlinear components, and their alignment, to get a deeper insight on the nature of the turbulent cascade. Finally, we compare our results with those from hybrid simulations with the same parameters, as well as with spacecraft observations.&lt;/p&gt;</jats:p>
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Journal articlePyakurel P, Phan T, Shay M, et al., 2022,
On the short-scale spatial variability of electron inflows in electron-only magnetic reconnection in the turbulent magnetosheath observed by MMS
<jats:p>&lt;p&gt;In the Earth&amp;#8217;s turbulent magnetosheath downstream of the quasiparallel bow shock region, magnetic reconnection without ion coupling was observed with bi-directional super-Alfv&amp;#233;nic electron jets. The lack of ion coupling was attributed to the small-scale sizes of the current sheets. In an electron-only reconnection event that occurred on 26 December 2016, we examine the detailed properties of electron inflows observed by all 4 MMS spacecraft. Even though the farthest MMS probe in the outflow direction from the X-line was no more than 8 electron skin depth, the electron inflows have significant asymmetry and highly variable amplitudes. We compare MMS observations with 2D-kinetic PIC simulation and find that the asymmetry in the inflow stems directly from the tilt of the out-of-plane (guide) magnetic field structure in the reconnection plane, with inflow asymmetry enhanced in the downstream region.&lt;/p&gt;</jats:p>
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Journal articleAdhikari S, Shay MA, Parashar TN, et al., 2022,
Reconnection and Turbulence: A Qualitative Approach to their Relationship
<jats:p>&lt;p&gt;Over the past few decades, the relationship between turbulence and reconnection has emerged as a subject of interest. For example, various properties of reconnection have been studied in different turbulent environments using plasma simulations. In other approaches, reconnection is studied as a subsidiary process occurring in turbulence. Turbulent features are also studied as consequences of instabilities associated with large scale reconnection. Only recently, we have attempted to answer some of the fundamental questions such as: &amp;#8220;What are the turbulent-like features of laminar magnetic reconnection?&amp;#8221;, &quot;Is magnetic reconnection fundamentally an energy cascade?&quot; both related to the interplay between reconnection and turbulence. Using 2.5D particle in cell simulations, we have found that laminar magnetic reconnection in a quasi-steady phase exhibits a Kolmogorov-like power spectrum. Most notably, the energy transfer process in magnetic reconnection is also found to be similar to that of a turbulent system suggesting that reconnection involves an energy cascade. The reconnection rate is correlated to both the magnetic energy spectrum in the ion-scales and the cascade of energy. Further, similarities between reconnection and turbulence in terms of the electric field spectrum, their components, and pressure-strain interaction will be highlighted.&lt;/p&gt;</jats:p>
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Journal articleRobertson S, Eastwood J, Stawarz J, et al., 2022,
Survey of EDR-associated Magnetopause Flux Ropes with MMS
<jats:p>&lt;p&gt;Flux ropes are twisted magnetic field structures produced during magnetic reconnection. They are thought to be important for energy transport and particle acceleration and are commonly observed throughout space plasma environments, including at the Earth&amp;#8217;s magnetopause. Flux Transfer Events (FTEs), which typically contain flux ropes, have been observed to grow in size and flux content as they are convected over the magnetopause and into the magnetotail, contributing to flux transport in the Dungey cycle. More recently, small-scale flux ropes have been observed inside the Electron Diffusion Region (EDR) during magnetopause reconnection.&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;br&gt;In this study, we investigate the link between the EDR and flux ropes, presenting a survey of 245 flux ropes observed by the Magnetospheric Multiscale (MMS) mission on days during which the spacecraft also encountered the EDR. MMS measures the thermal electron and ion 3D distributions at 30 msec and 150 msec time resolution, respectively, and at spacecraft separations down to a few kilometres allowing the study of such electron-scale phenomena. We find that flux ropes are more likely to be observed closer to the EDR, and that flux ropes observed closer to the EDR tend to have greater axial magnetic field strength and therefore greater flux content. We suggest that we could be sampling a subset of flux ropes that are recently formed by the EDR and discuss how this impacts current theories for flux rope evolution on the magnetopause.&lt;/p&gt;</jats:p>
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Journal articleStawarz JE, Eastwood JP, Phan T, et al., 2022,
Turbulence-driven magnetic reconnection and the magnetic correlation length in collisionless plasma turbulence
<jats:p>&lt;p&gt;&lt;span&gt;Observations of Earth&amp;#8217;s magnetosheath from the Magnetospheric Multiscale (MMS) mission have provided an unprecedented opportunity to examine the detailed structure of the multitude of thin current sheets that are generated by plasma turbulence, revealing that a novel form of magnetic reconnection, which has come to be known as electron-only reconnection, can occur within magnetosheath turbulence. These electron-only reconnection events occur at thin electron-scale current sheets and have super-Alfv&amp;#233;nic electron jets that can approach the electron Alfv&amp;#233;n speed; however, they do not appear to have signatures of ion jets. It is thought that electron-only reconnection can occur when the length of the reconnecting current sheets along the outflow direction is short enough that the ions cannot fully couple to the newly reconnected magnetic field lines before they fully relax. In this work, we examine how the correlation length of the magnetic fluctuations in a turbulent plasma, which constrains the length of the current sheets that can be formed by the turbulence, impacts the nature of turbulence-driven magnetic reconnection. Using observations from MMS, we systematically examine 60 intervals of magnetosheath turbulence &amp;#8211; identifying 256 small-scale reconnection events, both with and without ion jets. We demonstrate that the properties of the reconnection events transition to become more consistent with electron-only reconnection when the magnetic correlation length of the turbulence is below ~20 ion inertial lengths. We further discuss the implications of the results in the context of other turbulent plasmas by considering observations of turbulent fluctuations in the solar wind. &lt;br&gt;&lt;/span&gt;&lt;/p&gt;</jats:p>
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