Search or filter publications

Filter by type:

Filter by publication type

Filter by year:

to

Results

  • Showing results for:
  • Reset all filters

Search results

  • Journal article
    Nave 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 article
    Kasoar M, Hamilton D, Dalmonech D, Hantson S, Lasslop G, Voulgarakis A, Wells Cet al., 2021,

    Improved estimates of future fire emissions under CMIP6 scenarios and implications for aerosol radiative forcing

    <jats:p>&amp;lt;p&amp;gt;The CMIP6 Shared Socioeconomic Pathway (SSP) scenarios include projections of future changes in anthropogenic biomass-burning.&amp;amp;#160; Globally, they assume a decrease in total fire emissions over the next century under all scenarios.&amp;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.&amp;lt;/p&amp;gt;&amp;lt;p&amp;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;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;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.&amp;lt;/p&amp;gt;&amp;lt;p&amp;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;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;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

  • Journal article
    Millington J, Perkins O, Kasoar M, Voulgarakis Aet al., 2021,

    Advancing representation of anthropogenic fire in dynamic global vegetation models

    <jats:p>&amp;lt;div&amp;gt;&amp;lt;p&amp;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;amp;#160;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;/div&amp;gt;&amp;lt;div&amp;gt;&amp;lt;p&amp;gt;Our modelling of anthropogenic fire adopts an approach that classifies &amp;amp;#8216;agent functional types&amp;amp;#8217; (AFTs) to represent human fire activity based on land use/cover and Stephen Pyne&amp;amp;#8217;s fire development stages. For example, the &amp;amp;#8216;swidden&amp;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

  • Journal article
    Wells C, Voulgarakis A, 2021,

    The local and remote atmospheric impacts of Africa&amp;#8217;s 21st century aerosol emission trajectory

    <jats:p>&amp;lt;p&amp;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&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; concentrations, to investigate the impact of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;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;amp;#160;&amp;lt;/p&amp;gt;</jats:p>

  • Journal article
    Mansfield L, Nowack P, Voulgarakis A, 2021,

    Predicting climate model response to changing emissions

    <jats:p>&amp;lt;p&amp;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;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;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;amp;#160;&amp;lt;/p&amp;gt;</jats:p>

  • Conference paper
    Baran J, Rothkaehl H, Andre N, Auster U, Della Corte V, Edberg N, Galand M, Henri P, De Keyser J, Kolmasova I, Morawski M, Nilsson H, Prech L, Volwerk Met al., 2021,

    The challenges of&amp;#160; the Dust-Field-Plasma&amp;#160; (DFP) instrument onboard ESA &amp;#160;Comet Interceptor mission&amp;#160;

    <jats:p>&amp;lt;p&amp;gt;The&amp;amp;#160;flyby of a dynamically new comet by ESA-F1 Comet Interceptor spacecraft offers unique multi-point&amp;amp;#160;opportunities for studying the comet's dusty and ionised cometary &amp;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;amp;#160;a Plasma Package suite on the&amp;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.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The full diagnostics located on the board of the 3 spacecrafts will allow&amp;amp;#160; to modeling the comet environment and described the complex physical processes around the comet and on their surface including also the&amp;amp;#160; description of wave particle&amp;amp;#160; interaction in dusty cometary plasma.&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The full set of DFP instrument&amp;amp;#160;on &amp;amp;#160;board the Comet Interceptor &amp;amp;#160;spacecraft will allow&amp;amp;#160;to model &amp;amp;#160;the comet plasma&amp;amp;#160;environment and&amp;amp;#160;its interaction with the solar wind.&amp;amp;#160;It will also allow to&amp;amp;#160;describe&amp;amp;#160;the complex physical processes taking place including wave particle&amp;amp;#160;&amp;amp;#160;interaction in dusty cometary plasma .&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;On spacecraft A, DFP consists of a magne

  • Conference paper
    Stephenson P, Galand M, Deca J, Henri P, Carnielli Get al., 2021,

    Electron cooling at a weakly outgassing comet

    <jats:p>&amp;lt;p&amp;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 (&amp;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 &amp;lt; 10&amp;lt;sup&amp;gt;26&amp;lt;/sup&amp;gt; s&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt;), there should not be enough neutral molecules to cool the warm electrons efficiently before they ballistically escape the coma.&amp;lt;/p&amp;gt;&amp;lt;p&amp;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

  • Journal article
    Shebanits O, Hadid L, Cao H, Morooka M, Dougherty M, Wahlund J-E, Hunt G, Waite H, Müller-Wodarg Iet al., 2021,

    The conductive dusty ionosphere of Saturn

    <jats:p>&amp;lt;p&amp;gt;Cassini&amp;amp;#8217;s Grand Finale orbits brought us historical first in-situ measurements of Saturn&amp;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;amp;#8211; 12:17 Saturn Local Time, 10N &amp;amp;#8211; 20S planetocentric latitude), derived from particle and magnetometer data. We constrain the Pedersen conductivities to be at least 10&amp;lt;sup&amp;gt;-5&amp;lt;/sup&amp;gt; &amp;amp;#8211; 10&amp;lt;sup&amp;gt;-4&amp;lt;/sup&amp;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.&amp;lt;/p&amp;gt;</jats:p>

  • Conference paper
    Thomas C, Voulgarakis A, Lim G, Haigh J, Nowack Pet al., 2021,

    An unsupervised learning approach to identifying blocking events: the case of European summer

    <jats:p>&amp;lt;p&amp;gt;Atmospheric blocking events are mid-latitude weather patterns, which obstruct the usual path of the polar jet stream. Several blocking indices (BIs) have been developed to study blocking patterns and their associated trends, but these show significant seasonal and regional differences. Despite being central features of mid-latitude synoptic-scale weather, there is no well-defined historical dataset of blocking events. Here, we introduce a new blocking index using self-organizing maps (SOMs), an unsupervised machine learning approach, and compare its detection skill to some of the most widely applied BIs. To enable this intercomparison, we first create a new ground truth time series classification of European blocking based on expert judgement. We then demonstrate that our method (SOM-BI) has several key advantages over previous BIs because it exploits all the spatial information provided in the input data and avoids the need for arbitrary thresholds. Using ERA5 reanalysis data (1979-2019), we find that the SOM-BI identifies blocking events with a higher precision and recall than other BIs. We present a case study of the 2003 European heat wave and highlight that well-defined groups of SOM nodes can be an effective tool to reliably and accurately diagnose such weather events. This contrasts with the way SOMs are commonly used, where an individual SOM node can be wrongly assumed to represent a weather pattern. We also evaluate the SOM-BI performance on about 100 years of climate model data from a preindustrial simulation with the new UK Earth System Model (UK-ESM1). For the model data, all blocking detection methods have lower skill than for the ERA5 reanalysis, but SOM-BI performs significantly better than the conventional indices. This shows that our method can be effectively applied to climate models to develop our understanding of how climate change will affect regional blocking characteristics. Overall, our results demonstra

  • Journal article
    Good S, Kilpua E, Ala-Lahti M, Osmane A, Bale S, Zhao Let al., 2021,

    Cross helicity of magnetic clouds observed by Parker Solar Probe

    <jats:p>&amp;lt;p&amp;gt;Magnetic clouds are large-scale transient structures in the solar wind with low plasma &amp;lt;em&amp;gt;&amp;amp;#946;&amp;lt;/em&amp;gt;, low-amplitude magnetic field fluctuations, and twisted field lines with both ends often connected to the Sun. We analyse the normalised cross helicity, &amp;lt;em&amp;gt;&amp;amp;#963;&amp;lt;/em&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;gt;, and residual energy, &amp;lt;em&amp;gt;&amp;amp;#963;&amp;lt;/em&amp;gt;&amp;lt;sub&amp;gt;r&amp;lt;/sub&amp;gt;, in magnetic clouds observed by Parker Solar Probe (PSP). In the November 2018 cloud observed at 0.25 au, a low value of &amp;lt;em&amp;gt;&amp;amp;#963;&amp;lt;/em&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;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;amp;#8217;s outer layers displayed larger amplitude Alfv&amp;amp;#233;nic fluctuations with high &amp;lt;em&amp;gt;&amp;amp;#963;&amp;lt;/em&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;gt; values and &amp;lt;em&amp;gt;&amp;amp;#963;&amp;lt;/em&amp;gt;&amp;lt;sub&amp;gt;r&amp;lt;/sub&amp;gt; ~ 0. These properties are compared and contrasted to those found in clouds observed by PSP at larger heliocentric distances. We suggest that low &amp;lt;em&amp;gt;&amp;amp;#963;&amp;lt;/em&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;gt; is likely a common feature of magnetic clouds given their typically closed field structure, in contrast to the generally higher &amp;lt;em&amp;gt;&amp;amp;#963;&amp;lt;/em&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;gt; found on the open field lines of the solar wind.&amp;lt;/p&amp

  • Journal article
    Woolley T, Matteini L, Horbury TS, Laker R, Woodham LD, Bale SD, Stawarz JE, Berčič L, McManus MD, Badman STet al., 2021,

    Characterisation and comparison of slow coronal hole wind intervals at 0.13au

    <jats:p>&amp;lt;p&amp;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;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.&amp;lt;/p&amp;gt;</jats:p>

  • Journal article
    Stawarz J, Matteini L, Parashar T, Franci L, Eastwood J, Gonzalez C, Gingell I, Burch J, Ergun R, Ahmadi N, Giles B, Gershman D, Le Contel O, Lindqvist P-A, Russell C, Strangeway R, Torbert Ret al., 2021,

    Comparative Analysis of the Various Generalized Ohm's Law Terms in Magnetosheath Turbulence as Observed by Magnetospheric Multiscale

    <jats:p>&amp;lt;p&amp;gt;&amp;lt;span&amp;gt;Electric fields (&amp;lt;strong&amp;gt;E&amp;lt;/strong&amp;gt;) play a fundamental role in facilitating the exchange of energy between the electromagnetic fields and the changed particles within a plasma. &amp;lt;/span&amp;gt;Decomposing &amp;lt;strong&amp;gt;E&amp;lt;/strong&amp;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;amp;#8208;resolution, multi&amp;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&amp;lt;strong&amp;gt; &amp;lt;/strong&amp;gt;spectrum are examined observationally for the first time. The magnetohydrodynamic, Hall, and electron pressure terms are the dominant contributions to &amp;lt;strong&amp;gt;E&amp;lt;/strong&amp;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;amp;#8208;ion scales. The strength of the non&amp;amp;#8208;ideal electron pressure contribution is stronger than expected from linear kinetic Alfv&amp;amp;#233;n waves and a partial anti&amp;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 &amp;lt;strong&am

  • Journal article
    Chen C, Chandran B, Woodham L, Jones S, Perez J, Bourouaine S, Bowen T, Klein K, Moncuquet M, Kasper J, Bale Set al., 2021,

    The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration

    <jats:p>&amp;lt;p&amp;gt;The fourth orbit of Parker Solar Probe (PSP) reached heliocentric distances down to 27.9 Rs, allowing solar wind turbulence and acceleration mechanisms to be studied in situ closer to the Sun than previously possible. The turbulence properties were found to be significantly different in the inbound and outbound portions of PSP's fourth solar encounter, likely due to the proximity to the heliospheric current sheet (HCS) in the outbound period. Near the HCS, in the streamer belt wind, the turbulence was found to have lower amplitudes, higher magnetic compressibility, a steeper magnetic field spectrum (with spectral index close to -5/3 rather than -3/2), a lower Alfvenicity, and a &amp;quot;1/f&amp;quot; break at much lower frequencies. These are also features of slow wind at 1 au, suggesting the near-Sun streamer belt wind to be the prototypical slow solar wind. The transition in properties occurs at a predicted angular distance of ~4 degrees from the HCS, suggesting ~8 degrees as the full-width of the streamer belt wind at these distances. While the majority of the Alfvenic turbulence energy fluxes measured by PSP are consistent with those required for reflection-driven turbulence models of solar wind acceleration, the fluxes in the streamer belt are significantly lower than the model predictions, suggesting that additional mechanisms are necessary to explain the acceleration of the streamer belt solar wind.&amp;lt;/p&amp;gt;</jats:p>

  • Journal article
    Voigt A, Albern N, Ceppi P, Grise K, Li Y, Medeiros Bet al., 2021,

    Clouds, radiation, and atmospheric circulation in the present-day climate and under climate change

    , Wiley Interdisciplinary Reviews: WIREs Climate Change, Vol: 12, Pages: 1-22, ISSN: 1757-7780

    By interacting with radiation, clouds modulate the flow of energy through the Earth system, the circulation of the atmosphere, and regional climate. We review the impact of cloud‐radiation interactions for the atmospheric circulation in the present‐day climate, its internal variability and its response to climate change. After summarizing cloud‐controlling factors and cloud‐radiative effects, we clarify the scope and limits of the Clouds On‐Off Klimate Model Intercomparison Experiment (COOKIE) and cloud‐locking modeling methods. COOKIE showed that the presence of cloud‐radiative effects shapes the circulation in the present‐day climate in many important ways, including the width of the tropical rain belts and the position of the extratropical storm tracks. Cloud locking, in contrast, identified how clouds affect internal variability and the circulation response to global warming. This includes strong, but model‐dependent, shortwave and longwave cloud impacts on the El‐Nino Southern Oscillation, and the finding that most of the poleward circulation expansion in response to global warming can be attributed to radiative changes in clouds. We highlight the circulation impact of shortwave changes from low‐level clouds and longwave changes from rising high‐level clouds, and the contribution of these cloud changes to model differences in the circulation response to global warming. The review in particular draws attention to the role of cloud‐radiative heating within the atmosphere. We close by raising some open questions which, among others, concern the need for studying the cloud impact on regional scales and opportunities created by the next generation of global storm‐resolving models.

  • Journal article
    Morimoto S, Goto D, Murayama S, Fujita R, Tohjima Y, Ishidoya S, Machida T, Inai Y, Patra PK, Maksyutov S, Ito A, Aoki Set al., 2021,

    Spatio-temporal variations of the atmospheric greenhouse gases and their sources and sinks in the Arctic region

    , POLAR SCIENCE, Vol: 27, ISSN: 1873-9652
  • Journal article
    Wang L, Zong Q, Shi Q, Wimmer-Schweingruber RF, Bale SDet al., 2021,

    Solar Energetic Electrons Entering the Earth's Cusp/Lobe

    , ASTROPHYSICAL JOURNAL, Vol: 910, ISSN: 0004-637X
  • Journal article
    Xu S, Schwartz SJ, Mitchell DL, Horaites K, Andersson L, Halekas J, Mazelle C, Gruesbeck JRet al., 2021,

    Cross-Shock Electrostatic Potentials at Mars Inferred From MAVEN Measurements

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380
  • Journal article
    Provan G, Bradley TJ, Bunce EJ, Cowley SWH, Cao H, Dougherty M, Hunt GJ, Roussos E, Staniland NR, Tao Cet al., 2021,

    Saturn's Nightside Ring Current During Cassini's Grand Finale

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380
  • Journal article
    Klein KG, Verniero JL, Alterman B, Bale S, Case A, Kasper JC, Korreck K, Larson D, Lichko E, Livi R, McManus M, Martinovic M, Rahmati A, Stevens M, Whittlesey Pet al., 2021,

    Inferred Linear Stability of Parker Solar Probe Observations Using One- and Two-component Proton Distributions

    , ASTROPHYSICAL JOURNAL, Vol: 909, ISSN: 0004-637X
  • Journal article
    He J, Cui B, Yang L, Hou C, Zhang L, Ip W-H, Jia Y-D, Dong C, Duan D, Zong Q, Bale SD, Pulupa M, Bonnell JW, Dudok De Wit T, Goetz K, Harvey PR, MacDowall RJ, Malaspina DMet al., 2021,

    The Encounter of the Parker Solar Probe and a Comet-like Object Near the Sun: Model Predictions and Measurements

    , ASTROPHYSICAL JOURNAL, Vol: 910, ISSN: 0004-637X
  • Journal article
    Huang SY, Sahraoui F, Andres N, Hadid LZ, Yuan ZG, He JS, Zhao JS, Galtier S, Zhang J, Deng XH, Jiang K, Yu L, Xu SB, Xiong QY, Wei YY, Dudok de Wit T, Bale SD, Kasper JCet al., 2021,

    The Ion Transition Range of Solar Wind Turbulence in the Inner Heliosphere: Parker Solar Probe Observations

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 909, ISSN: 2041-8205
  • Journal article
    Schwartz SJ, Kucharek H, Farrugia CJ, Trattner K, Gingell I, Ergun RE, Strangeway R, Gershman Det al., 2021,

    Energy Conversion Within Current Sheets in the Earth's Quasi-Parallel Magnetosheath

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 48, ISSN: 0094-8276
  • Journal article
    Heyns MJ, Lotz SI, Gaunt CT, 2021,

    Geomagnetic Pulsations Driving Geomagnetically Induced Currents

    , Space Weather, Vol: 19, ISSN: 1542-7390

    <jats:title>Abstract</jats:title> <jats:p> Geomagnetically induced currents (GICs) are driven by the geoelectric field induced by fluctuations of Earth's magnetic field. Drivers of intense GICs are often associated with large impulsive events such as coronal mass ejections. To a lesser extent fluctuations from regular oscillations of the geomagnetic field, or geomagnetic pulsations, have also been identified as possible drivers of GICs. In this work we show that these low‐frequency pulsations are directly observed in measured GIC data from power networks. Due to the low‐pass nature of GICs, Pc5 and lower‐frequency pulsations drive significant GICs for an extended duration even at midlatitudes. Longer‐period Ps6‐type disturbances apparently not typical of midlatitudes are seen with GIC amplitudes comparable to the peak GIC at storm sudden commencement. The quasi‐ac (alternating current) nature of the sustained pulsation driving affects the power system response and cannot be properly modeled using only direct current (dc) models. A further consideration is that the often used <jats:styled-content> <jats:italic>d</jats:italic> <jats:italic>B</jats:italic> / <jats:italic>d</jats:italic> <jats:italic>t</jats:italic> </jats:styled-content> GIC proxy is biased to the sampling rate of the geomagnetic field measurements used. The <jats:styled-content> <jats:italic>d</jats:italic> <jats:italic>B</jats:italic> / <jats:italic>d</jats:italic> <jats:italic>t</jats:italic> </jats:styled-content>

  • Journal article
    Archer MO, Day N, Barnes S, 2021,

    Demonstrating change from a drop-in space soundscape exhibit by using graffiti walls both before and after

    , Geoscience Communication, Vol: 4, Pages: 57-67, ISSN: 2569-7110

    Impact evaluation in public engagement necessarily requires measuring change. However, this is extremely challenging for drop-in activities due to their very nature. We present a novel method of impact evaluation which integrates graffiti walls into the experience both before and after the main drop-in activity. The activity in question was a soundscape exhibit, where young families experienced the usually inaudible sounds of near-Earth space in an immersive and accessible way. We apply two analysis techniques to the captured before and after data – quantitative linguistics and thematic analysis. These analyses reveal significant changes in participants' responses after the activity compared to before, namely an increased diversity in language used to describe space and altered conceptions of what space is like. The results demonstrate that the soundscape was surprisingly effective at innately communicating key aspects of the underlying science simply through the act of listening. The impacts also highlight the power of sonification in stimulating public engagement, which, through reflection, can lead to altered associations, perceptions, and understanding. Therefore, we show that this novel approach to drop-in activity evaluation, using graffiti walls both before and after the activity and applying rigorous analysis to this data, has the power to capture change and, thus, have a short-term impact. We suggest that commonly used evaluation tools suitable for drop-in activities, such as graffiti walls, should be integrated both before and after the main activity in general, rather than only using them afterwards as is typically the case.

  • Journal article
    Allen RC, Ho GC, Mason GM, Li G, Jian LK, Vines SK, Schwadron NA, Joyce CJ, Bale SD, Bonnell JW, Case AW, Christian ER, Cohen CMS, Desai M, Filwett R, Goetz K, Harvey PR, Hill ME, Kasper JC, Korreck KE, Lario D, Larson D, Livi R, MacDowall RJ, Malaspina DM, McComas DJ, McNutt R, Mitchell DG, Paulson KW, Pulupa M, Raouafi N, Stevens ML, Whittlesey PL, Wiedenbeck Met al., 2021,

    Radial Evolution of a CIR: Observations From a Nearly Radially Aligned Event Between Parker Solar Probe and STEREO-A

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 48, ISSN: 0094-8276
  • Journal article
    Archer M, DeWitt J, Davenport C, Keenan O, Coghill L, Christodoulou A, Durbin S, Campbell H, Hou Let al., 2021,

    Going beyond the one-off: How can STEM engagement programmes with young people have real lasting impact?

    , Research for All, Vol: 5, Pages: 67-85, ISSN: 2399-8121

    A major focus in the STEM public engagement sector concerns engaging withyoung people, typically through schools. The aims of these interventions areoften to positively affect students' aspirations towards continuing STEMeducation and ultimately into STEM-related careers. Most schools engagementactivities take the form of short one-off interventions that, while able toachieve positive outcomes, are limited in the extent to which they can havelasting impacts on aspirations. In this paper we discuss various differentemerging programmes of repeated interventions with young people, assessing whatimpacts can realistically be expected. Short series of interventions appearalso to suffer some limitations in the types of impacts achievable. However,deeper programmes that interact with both young people and those that influencethem over significant periods of time (months to years) seem to be moreeffective in influencing aspirations. We discuss how developing a Theory ofChange and considering young people's wider learning ecologies are required inenabling lasting impacts in a range of areas. Finally, we raise severalsector-wide challenges to implementing and evaluating these emergingapproaches.

  • Journal article
    Liou K, Paranicas C, Vines S, Kollmann P, Allen R, Clark G, Mitchell D, Jackman C, Masters A, Achilleos N, Roussos E, Krupp Net al., 2021,

    Dawn-dusk asymmetry in energetic (>20 keV) particles adjacent to Saturn's magnetopause

    , Journal of Geophysical Research: Space Physics, Vol: 126, ISSN: 2169-9380

    Energetic particles (>∼25 keV) have been observed routinely in the terrestrial magnetosheath, but have not been well studied at the magnetosheaths of the outer planets. Here we analyze energetic electrons and ions (mostly protons) in the vicinity (±1 RS) of Saturn's magnetopause, using particle data acquired with the low‐energy magnetosphere measurements system, one of the three sensors of the magnetosphere imaging instrument on board the Cassini spacecraft, during a period of ∼14 years (2004–2017). It is found that energetic particles, especially ions, are also common in Saturn's magnetosheath. A clear inward (toward Saturn) gradient in the electron differential flux is identified, suggestive of magnetospheric sources. Such an inward gradient does not appear in some of the ion channels. We conclude that Saturn's magnetopause acts as a porous barrier for energetic electrons and, to a lesser extent, for energetic ions. A dawn‐dusk asymmetry in the gradient of particle flux across the magnetopause is also identified, with a gradual decrease at the dawn and a sharp decrease at the dusk magnetopause. It is also found that magnetic reconnection enhanced flux levels just outside of the magnetopause, with evidence suggesting that these particles are from magnetospheric sources. These findings strongly suggest that Saturn's magnetosphere is most likely the main source of energetic particles in Saturn's magnetosheath and magnetosphere leakage is an important process responsible for the presence of the energetic particles in Saturn's magnetosheath.

  • Journal article
    Zappa G, Ceppi P, Shepherd TG, 2021,

    Eurasian cooling in response to Arctic sea-ice loss is not proved by maximum covariance analysis

    , Nature Climate Change, Vol: 11, Pages: 106-108, ISSN: 1758-678X
  • Journal article
    Sparks N, Toumi R, 2021,

    On the seasonal and sub-seasonal factors influencing East China tropical cyclone landfall

    , Atmospheric Science Letters, Vol: 22, Pages: 1-8, ISSN: 1530-261X

    To date it has proved difficult to make seasonal forecasts of tropical cyclones, particularly for landfall and in East China specifically. This study examines sources of predictability for the number of landfalling typhoons in East China on seasonal (June–October) and sub‐seasonal time scales. East China landfall count is shown to be independent of basin‐scale properties of TC tracks, such the genesis location, duration, basin track direction and length, and basin total count. Large‐scale environmental climate indices which are potential basin scale drivers are also shown to be largely uncorrelated with landfall prior to and throughout the season. The most important factor is the steering in the final stages to landfall. The seasonal landfall is strongly anti‐correlated with the more local zonal mid‐tropospheric wind field over the East China sea (r = −.61, p < .001). It is proposed that geopotential height anomalies over Korea/Japan cause anomalous easterly winds in the East China Sea and enhance landfall rates by steering typhoons onto the coast. Early, peak, and late sub‐seasonal landfall counts are shown to be independent of each other yet share this predictor. This local feature may be dynamically predictable allowing a potential hybrid dynamical‐statistical seasonal forecast of landfall.

  • Journal article
    Southwood DJ, Cao H, Shebanits O, Elsden T, Hunt GJ, Dougherty MKet al., 2021,

    Discovery of Alfven waves planetward of Saturn's rings

    , Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-18, ISSN: 2169-9380

    Between April and September 2017 in the final stages of the Cassini Saturn Orbiter mission the spacecraft executed 22 orbits passing planetward of the innermost ring, the D-ring. During all periapsis passes oscillations were detected in the azimuthal magnetic field components on typical time scales of a few minutes. We argue that these time-varying magnetic signals detected on the spacecraft are also primarily time-varying in the plasma frame. Furthermore, we show that nearly all signals exhibit a spatial feature, namely a magnetic node near the effective field line equator. We propose that the oscillations are associated with Alfvén waves excited in local field line resonances, most likely driven from global sources.

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://www.imperial.ac.uk:80/respub/WEB-INF/jsp/search-t4-html.jsp Request URI: /respub/WEB-INF/jsp/search-t4-html.jsp Query String: id=214&limit=30&page=29&respub-action=search.html Current Millis: 1771194986949 Current Time: Sun Feb 15 22:36:26 GMT 2026