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  • Journal article
    Wilder FD, Schwartz SJ, Ergun RE, Eriksson S, Ahmadi N, Chasapis A, Newman DL, Burch JL, Torbert RB, Strangeway RJ, Giles BLet al., 2020,

    Parallel Electrostatic Waves Associated With Turbulent Plasma Mixing in the Kelvin-Helmholtz Instability

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 47, ISSN: 0094-8276
  • Journal article
    Fujita R, Morimoto S, Maksyutov S, Kim H-S, Arshinov M, Brailsford G, Aoki S, Nakazawa Tet al., 2020,

    Global and Regional CH<sub>4</sub>Emissions for 1995-2013 Derived From Atmospheric CH<sub>4</sub>, δ<SUP>13</SUP>C-CH<sub>4</sub>, and δD-CH<sub>4</sub>Observations and a Chemical Transport Model

    , JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, Vol: 125, ISSN: 2169-897X
  • Journal article
    Gibbins G, Haigh JD, 2020,

    Entropy production rates of the climate

    , Journal of the Atmospheric Sciences, ISSN: 0022-4928

    There is ongoing interest in the global entropy production rate as a climate diagnostic and predictor, but progress has been limited by ambiguities in its definition; different conceptual boundaries of the climate system give rise to different internal production rates. Three viable options are described, estimated and investigated here, two of which -- the material and the total radiative (here `planetary') entropy production rates -- are well-established and a third which has only recently been considered but appears very promising. This new option is labelled the `transfer' entropy production rate and includes all irreversible processes that transfer heat within the climate, radiative and material, but not those involved in the exchange of radiation with space. Estimates in three model climates put the material rate in the range 27-48 mW/m^2K, the transfer rate 67-76mW/m^2K, and the planetary rate 1279-1312 mW/m^2K. The climate-relevance of each rate is probed by calculating their responses to climate changes in a simple radiative-convective model. An increased greenhouse effect causes a significant increase in the material and transfer entropy production rates but has no direct impact on the planetary rate. When the same surface temperature increase is forced by changing the albedo instead, the material and transfer entropy production rates increase less dramatically and the planetary rate also registers an increase. This is pertinent to solar radiation management as it demonstrates the difficulty of reversing greenhouse gas-mediated climate changes by albedo alterations. It is argued that the transfer perspective has particular significance in the climate system and warrants increased prominence.
  • Journal article
    AkhavanTafti M, Palmroth M, Slavin JA, Battarbee M, Ganse U, Grandin M, Le G, Gershman DJ, Eastwood JP, Stawarz JEet al., 2020,

    Comparative analysis of the vlasiator simulations and MMS observations of multiple X‐line reconnection and flux transfer events

    , Journal of Geophysical Research: Space Physics, Vol: 125, Pages: 1-22, ISSN: 2169-9380

    The Vlasiator hybrid‐Vlasov code was developed to investigate global magnetospheric dynamics at ion‐kinetic scales. Here, we focus on the role of magnetic reconnection in the formation and evolution of the magnetic islands at the low‐latitude magnetopause, under southward interplanetary magnetic field (IMF) conditions. The simulation results indicate that: 1) the magnetic reconnection ion kinetics, including the Earthward‐pointing Larmor electric field on the magnetospheric‐side of an X‐point and anisotropic ion distributions, are well‐captured by Vlasiator, thus enabling the study of reconnection‐driven magnetic island evolution processes, 2) magnetic islands evolve due to continuous reconnection at adjacent X‐points, ‘coalescence’ which refers to the merging of neighboring islands to create a larger island, ‘erosion’ during which an island loses magnetic flux due to reconnection, and ‘division’ which involves the splitting of an island into smaller islands, and 3) continuous reconnection at adjacent X‐points is the dominant source of magnetic flux and plasma to the outer layers of magnetic islands resulting in cross‐sectional growth rates up to +0.3 RE2/min. The simulation results are compared to the Magnetospheric Multiscale (MMS) measurements of a chain of ion‐scale flux transfer events (FTEs) sandwiched between two dominant X‐lines. The MMS measurements similarly reveal: 1) anisotropic ion populations, and 2) normalized reconnection rate ~0.18, in agreement with theory and the Vlasiator predictions. Based on the simulation results and the MMS measurements, it is estimated that the observed ion‐scale FTEs may grow Earth‐sized within ~10 minutes, which is comparable to the average transport time for FTEs formed in the subsolar region to the high‐latitude magnetopause. Future simulations shall revisit reconnection‐driven island evolution processes with improved spatial resolutions.
  • Journal article
    Eggington JWB, Eastwood JP, Mejnertsen L, Desai RT, Chittenden JPet al., 2020,

    Dipole tilt effect on magnetopause reconnection and the steady‐state magnetosphere‐ionosphere system: global MHD simulation

    , Journal of Geophysical Research: Space Physics, Vol: 125, Pages: 1-17, ISSN: 2169-9380

    The Earth’s dipole tilt angle changes both diurnally and seasonally and introduces numerous variabilities in the coupled magnetosphere‐ionosphere system. By altering the location and intensity of magnetic reconnection, the dipole tilt influences convection on a global scale. However, due to the nonlinear nature of the system, various other effects like dipole rotation, varying IMF orientation and non‐uniform ionospheric conductance can smear tilt effects arising purely from changes in coupling with the solar wind. To elucidate the underlying tilt angle‐dependence, we perform MHD simulations of the steady‐state magnetosphere‐ionosphere system under purely southward IMF conditions for tilt angles from 0°‐90°. We identify the location of the magnetic separator in each case, and find that an increasing tilt angle shifts the 3‐D X‐line southward on the magnetopause due to changes in magnetic shear angle. The separator is highly unsteady above 50° tilt angle, characteristic of regular FTE generation on the magnetopause. The reconnection rate drops as the tilt angle becomes large, but remains continuous across the dayside such that the magnetosphere is open even for 90°. These trends map down to the ionosphere, with the polar cap contracting as the tilt angle increases, and region‐I field‐aligned current (FAC) migrating to higher latitudes with changing morphology. The tilt introduces a north‐south asymmetry in magnetospheric convection, thus driving more FAC in the northern (sunward‐facing) hemisphere for large tilt angles than in the south independent of conductance. These results highlight the strong sensitivity to onset time in the potential impact of a severe space weather event.
  • Journal article
    Hantson S, Kelley DI, Arneth A, Harrison SP, Archibald S, Bachelet D, Forrest M, Hickler T, Lasslop G, Li F, Mangeon S, Melton JR, Nieradzik L, Rabin SS, Prentice IC, Sheehan T, Sitch S, Teckentrup L, Voulgarakis A, Yue Cet al., 2020,

    Quantitative assessment of fire and vegetation properties in simulations with fire-enabled vegetation models from the Fire Model Intercomparison Project

    , Geoscientific Model Development, Vol: 13, Pages: 3299-3318, ISSN: 1991-959X

    Global fire-vegetation models are widely used to assess impacts of environmental change on fire regimes and the carbon cycle and to infer relationships between climate, land use and fire. However, differences in model structure and parameterizations, in both the vegetation and fire components of these models, could influence overall model performance, and to date there has been limited evaluation of how well different models represent various aspects of fire regimes. The Fire Model Intercomparison Project (FireMIP) is coordinating the evaluation of state-of-the-art global fire models, in order to improve projections of fire characteristics and fire impacts on ecosystems and human societies in the context of global environmental change. Here we perform a systematic evaluation of historical simulations made by nine FireMIP models to quantify their ability to reproduce a range of fire and vegetation benchmarks. The FireMIP models simulate a wide range in global annual total burnt area (39–536 Mha) and global annual fire carbon emission (0.91–4.75 Pg C yr−1) for modern conditions (2002–2012), but most of the range in burnt area is within observational uncertainty (345–468 Mha). Benchmarking scores indicate that seven out of nine FireMIP models are able to represent the spatial pattern in burnt area. The models also reproduce the seasonality in burnt area reasonably well but struggle to simulate fire season length and are largely unable to represent interannual variations in burnt area. However, models that represent cropland fires see improved simulation of fire seasonality in the Northern Hemisphere. The three FireMIP models which explicitly simulate individual fires are able to reproduce the spatial pattern in number of fires, but fire sizes are too small in key regions, and this results in an underestimation of burnt area. The correct representation of spatial and seasonal patterns in vegetation appears
  • Journal article
    Tang T, Shindell D, Zhang Y, Voulgarakis A, Lamarque J-F, Myhre G, Stjern CW, Faluvegi G, Samset BHet al., 2020,

    Response of surface shortwave cloud radiative effect to greenhouse gases and aerosols and its impact on summer maximum temperature

    , Atmospheric Chemistry and Physics, Vol: 20, Pages: 8251-8266, ISSN: 1680-7316

    Shortwave cloud radiative effects (SWCREs), defined as the difference of the shortwave radiative flux between all-sky and clear-sky conditions at the surface, have been reported to play an important role in influencing the Earth's energy budget and temperature extremes. In this study, we employed a set of global climate models to examine the SWCRE responses to CO2, black carbon (BC) aerosols, and sulfate aerosols in boreal summer over the Northern Hemisphere. We found that CO2 causes positive SWCRE changes over most of the NH, and BC causes similar positive responses over North America, Europe, and eastern China but negative SWCRE over India and tropical Africa. When normalized by effective radiative forcing, the SWCRE from BC is roughly 3–5 times larger than that from CO2. SWCRE change is mainly due to cloud cover changes resulting from changes in relative humidity (RH) and, to a lesser extent, changes in cloud liquid water, circulation, dynamics, and stability. The SWCRE response to sulfate aerosols, however, is negligible compared to that for CO2 and BC because part of the radiation scattered by clouds under all-sky conditions will also be scattered by aerosols under clear-sky conditions. Using a multilinear regression model, it is found that mean daily maximum temperature (Tmax) increases by 0.15 and 0.13 K per watt per square meter (W m−2) increase in local SWCRE under the CO2 and BC experiment, respectively. When domain-averaged, the contribution of SWCRE change to summer mean Tmax changes was 10 %–30 % under CO2 forcing and 30 %–50 % under BC forcing, varying by region, which can have important implications for extreme climatic events and socioeconomic activities.
  • Journal article
    Saunois M, Stavert AR, Poulter B, Bousquet P, Canadell JG, Jackson RB, Raymond PA, Dlugokencky EJ, Houweling S, Patra PK, Ciais P, Arora VK, Bastviken D, Bergamaschi P, Blake DR, Brailsford G, Bruhwiler L, Carlson KM, Carrol M, Castaldi S, Chandra N, Crevoisier C, Crill PM, Covey K, Curry CL, Etiope G, Frankenberg C, Gedney N, Hegglin M, Hoglund-Isaksson L, Hugelius G, Ishizawa M, Ito A, Janssens-Maenhout G, Jensen KM, Joos F, Kleinen T, Krummel PB, Langenfelds RL, Laruelle GG, Liu L, Machida T, Maksyutov S, McDonald KC, McNorton J, Miller PA, Melton JR, Morino I, Muller J, Murguia-Flores F, Naik V, Niwa Y, Noce S, Doherty SO, Parker RJ, Peng C, Peng S, Peters GP, Prigent C, Prinn R, Ramonet M, Regnier P, Riley WJ, Rosentreter JA, Segers A, Simpson IJ, Shi H, Smith SJ, Steele LP, Thornton BF, Tian H, Tohjima Y, Tubiello FN, Tsuruta A, Viovy N, Voulgarakis A, Weber TS, van Weele M, van der Werf GR, Weiss RF, Worthy D, Wunch D, Yin Y, Yoshida Y, Zhang W, Zhang Z, Zhao Y, Zheng B, Zhu Q, Zhu Q, Zhuang Qet al., 2020,

    The global methane budget 2000-2017

    , Earth System Science Data, Vol: 12, Pages: 1561-1623, ISSN: 1866-3508

    Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 continue to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). The relative importance of CH4 compared to CO2 depends on its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in reducing uncertainties in the atmospheric growth rate arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations).For the 2008–2017 decade, global methane emissions are estimated by atmospheric inversions (a top-down approach) to be 576 Tg CH4 yr−1 (range 550–594, corresponding to the minimum and maximum estimates of the model ensemble). Of this total, 359 Tg CH4 yr−1 or ∼ 60 % is attributed to anthropogenic sources, that is emissions caused by direct human activity (i.e. anthropogenic emissions; range 336–376 Tg CH4 yr−1 or
  • Journal article
    Milillo, Fujimoto, Murakami, Benkhoff, Zender, Aizawa, Dósa, Griton, Heyner, Ho, Imber, Jia, Karlsson, Killen, Laurenza, Lindsay, McKenna-Lawlor, Mura, Raines, Rothery, André, Baumjohann, Berezhnoy, Bourdin, Bunce, Califano, Deca, de la Fuente, Dong, Grava, Fatemi, Henri, Ivanovski, Jackson, James, Kallio, Kasaba, Kilpua, Kobayashi, Langlais, Leblanc, Lhotka, Mangano, Martindale, Massetti, Masters A, Morooka, Narita, Oliveira, Odstrcil, Orsini, Pelizzo, Plainaki, Plaschke, Sahraoui, Seki, Slavin, Vainio, Wurz, Barabash, Carr C, Delcourt, Glassmeier, Grande, Hirahara, Huovelin, Korablev, Kojima, Lichtenegger, Livi, Matsuoka, Moissl, Moncuquet, Muinonen, Quèmerais, Saito, Yagitani, Yoshikawa, Wahlundet al., 2020,

    Investigating Mercury’s environment with the two-spacecraft BepiColombo mission

    , Space Science Reviews, Vol: 216, Pages: 1-78, ISSN: 0038-6308

    The ESA-JAXA BepiColombo mission will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric dynamics at Mercury as well as their interactions with the solar wind, radiation, and interplanetary dust. Many scientific instruments onboard the two spacecraft will be completely, or partially devoted to study the near-space environment of Mercury as well as the complex processes that govern it. Many issues remain unsolved even after the MESSENGER mission that ended in 2015. The specific orbits of the two spacecraft, MPO and Mio, and the comprehensive scientific payload allow a wider range of scientific questions to be addressed than those that could be achieved by the individual instruments acting alone, or by previous missions. These joint observations are of key importance because many phenomena in Mercury’s environment are highly temporally and spatially variable. Examples of possible coordinated observations are described in this article, analysing the required geometrical conditions, pointing, resolutions and operation timing of different BepiColombo instruments sensors.
  • Journal article
    Stawarz JE, Matteini L, Parashar TN, Franci L, Eastwood JP, Gonzalez CA, Gingell I, Burch JL, Ergun RE, Ahmadi N, Giles BL, Gershman DJ, Le Contel O, Lindqvist P-A, Russell CT, Strangeway RJ, Torbert RBet al., 2020,

    Generalized Ohm's Law Decomposition of the Electric Field in Magnetosheath Turbulence: Magnetospheric Multiscale Observations
  • Journal article
    Liu TZ, Hietala H, Angelopoulos V, Vainio R, Omelchenko Yet al., 2020,

    Electron acceleration by magnetosheath jet‐driven bow waves

    , Journal of Geophysical Research: Space Physics, Vol: 125, Pages: 1-13, ISSN: 2169-9380

    Magnetosheath jets are localized fast flows with enhanced dynamic pressure. When they supermagnetosonically compress the ambient magnetosheath plasma, a bow wave or shock can form ahead of them. Such a bow wave was recently observed to accelerate ions and possibly electrons. The ion acceleration process was previously analyzed, but the electron acceleration process remains largely unexplored. Here we use multi‐point observations by Time History of Events and Macroscale during Substorms from three events to determine whether and how magnetosheath jet‐driven bow waves can accelerate electrons. We show that when suprathermal electrons in the ambient magnetosheath convect towards a bow wave, some electrons are shock‐drift accelerated and reflected towards the ambient magnetosheath and others continue moving downstream of the bow wave resulting in bi‐directional motion. Our study indicates that magnetosheath jet‐driven bow waves can result in additional energization of suprathermal electrons in the magnetosheath. It implies that magnetosheath jets can increase the efficiency of electron acceleration at planetary bow shocks or other similar astrophysical environments.
  • Journal article
    Liu TZ, Hietala H, Angelopoulos V, Omelchenko Y, Vainio R, Plaschke Fet al., 2020,

    Statistical study of magnetosheath jet‐driven bow waves

    , Journal of Geophysical Research: Space Physics, Vol: 125, Pages: 1-14, ISSN: 2169-9380

    When a magnetosheath jet (localized dynamic pressure enhancements) compresses ambient magnetosheath at a (relative) speed faster than the local magnetosonic speed, a bow wave or shock can form ahead of the jet. Such bow waves or shocks were recently observed to accelerate particles, thus contributing to magnetosheath heating and particle acceleration in the extended environment of Earth’s bow shock. To further understand the characteristics of jet‐driven bow waves, we perform a statistical study to examine which solar wind conditions favor their formation and whether it is common for them to accelerate particles. We identified 364 out of 2859 (~13%) magnetosheath jets to have a bow wave or shock ahead of them with Mach number typically larger than 1.1. We show that large solar wind plasma beta, weak interplanetary magnetic field (IMF) strength, large solar wind Alfvén Mach number, and strong solar wind dynamic pressure present favorable conditions for their formation. We also show that magnetosheath jets with bow waves or shocks are more frequently associated with higher maximum ion and electron energies than those without them, confirming that it is common for these structures to accelerate particles. In particular, magnetosheath jets with bow waves have electron energy flux enhanced on average by a factor of 2 compared to both those without bow waves and the ambient magnetosheath. Our study implies that magnetosheath jets can contribute to shock acceleration of particles especially for high Mach number shocks. Therefore, shock models should be generalized to include magnetosheath jets and concomitant particle acceleration.
  • Journal article
    Bowen TA, Mallet A, Bale SD, Bonnell JW, Case AW, Chandran BDG, Chasapis A, Chen CHK, Duan D, de Wit TD, Goetz K, Halekas JS, Harvey PR, Kasper JC, Korreck KE, Larson D, Livi R, MacDowall RJ, Malaspina DM, McManus MD, Pulupa M, Stevens M, Whittlesey Pet al., 2020,

    Constraining Ion-Scale Heating and Spectral Energy Transfer in Observations of Plasma Turbulence

    , PHYSICAL REVIEW LETTERS, Vol: 125, ISSN: 0031-9007
  • Journal article
    Cao H, Dougherty MK, Hunt GJ, Provan G, Cowley SWH, Bunce EJ, Kellock S, Stevenson DJet al., 2020,

    The landscape of Saturn's internal magnetic field from the Cassini Grand Finale

    , ICARUS, Vol: 344, ISSN: 0019-1035
  • Journal article
    Diaz-Aguado MF, Bonnell JW, Bale SD, Christensen J, Lundgreen P, Lee J, Dennison JR, Wood B, Gruntman Met al., 2020,

    Experimental Investigation of the Secondary and Backscatter Electron Emission from Spacecraft Materials

    , JOURNAL OF SPACECRAFT AND ROCKETS, Vol: 57, Pages: 793-808, ISSN: 0022-4650
  • Journal article
    Martin CJ, Ray LC, Constable DA, Southwood DJ, Lorch CTS, Felici Met al., 2020,

    Evaluating the ionospheric mass source for Jupiter's magnetosphere: An ionospheric outflow model for the auroral regions

    , Journal of Geophysical Research: Space Physics, Vol: 125, ISSN: 2169-9380

    Ionospheric outflow is the flow of plasma initiated by a loss of equilibrium along a magnetic field line which induces an ambipolar electric field due to the separation of electrons and ions in a gravitational field and other mass dependant sources. We have developed an ionospheric outflow model using the transport equations to determine the number of particles that flow into the outer magnetosphere of Jupiter. The model ranges from 1400 km in altitude above the 1 bar level to 2.5 RJ along the magnetic field line and considers H+ and H3+ as the main ion constituents. Previously, only pressure gradients and gravitational forces were considered in modelling polar wind. However, at Jupiter we need to evaluate the affect of field‐aligned currents present in the auroral regions due to the breakdown of corotation in the magnetosphere, along with the centrifugal force exerted on the particles due to the fast planetary rotation rate. The total number flux from both hemispheres is found to be 1.3‐1.8 x 1028 s‐1 comparable in total number flux to the Io plasma source. The mass flux is lower due to the difference in ion species. This influx of protons from the ionosphere into the inner and middle magnetosphere needs to be included in future assessments of global flux tube dynamics and composition of the magnetosphere system.
  • Journal article
    Oliveros JCM, Diaz Castillo SM, Krupar V, Pulupa M, Bale SD, Calvo-Mozo Bet al., 2020,

    An In Situ Interplanetary "U-burst": Observation and Results

    , ASTROPHYSICAL JOURNAL, Vol: 897, ISSN: 0004-637X
  • Journal article
    Starkey M, Fuselier SA, Desai MI, Schwartz SJ, Gomez RG, Mukherjee J, Cohen IJ, Russell CTet al., 2020,

    MMS Observations of Accelerated Interstellar Pickup He<SUP>+</SUP>Ions at an Interplanetary Shock

    , ASTROPHYSICAL JOURNAL, Vol: 897, ISSN: 0004-637X
  • Journal article
    Huang SY, Zhang J, Sahraoui F, He JS, Yuan ZG, Andres N, Hadid LZ, Deng XH, Jiang K, Yu L, Xiong QY, Wei YY, Xu SB, Bale SD, Kasper JCet al., 2020,

    Kinetic Scale Slow Solar Wind Turbulence in the Inner Heliosphere: Coexistence of Kinetic Alfven Waves and Alfven Ion Cyclotron Waves

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 897, ISSN: 2041-8205
  • Journal article
    Oleynik P, Vainio R, Punkkinen A, Dudnik O, Gieseler J, Hedman H-P, Hietala H, Hæggström E, Niemelä P, Peltonen J, Praks J, Punkkinen R, Säntti T, Valtonen Eet al., 2020,

    Calibration of RADMON radiation monitor onboard Aalto-1 CubeSat

    , Advances in Space Research, Vol: 66, Pages: 42-51, ISSN: 0273-1177
  • Journal article
    Gieseler J, Oleynik P, Hietala H, Vainio R, Hedman H-P, Peltonen J, Punkkinen A, Punkkinen R, Säntti T, Hæggström E, Praks J, Niemelä P, Riwanto B, Jovanovic N, Mughal MRet al., 2020,

    Radiation monitor RADMON aboard Aalto-1 CubeSat: First results

    , Advances in Space Research, Vol: 66, Pages: 52-65, ISSN: 0273-1177
  • Journal article
    Magurno D, Cossich W, Maestri T, Bantges R, Brindley H, Fox S, Harlow C, Murray J, Pickering J, Warwick L, Oetjen Het al., 2020,

    Cirrus cloud identification from airborne far-infrared and mid-infrared spectra

    , Remote Sensing, Vol: 12, Pages: 1-19, ISSN: 2072-4292

    Airborne interferometric data, obtained from the Cirrus Coupled Cloud-Radiation Experiment (CIRCCREX) and from the PiknMix-F field campaign, are used to test the ability of a machine learning cloud identification and classification algorithm (CIC). Data comprise a set of spectral radiances measured by the Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) and the Airborne Research Interferometer Evaluation System (ARIES). Co-located measurements of the two sensors allow observations of the upwelling radiance for clear and cloudy conditions across the far- and mid-infrared part of the spectrum. Theoretical sensitivity studies show that the performance of the CIC algorithm improves with cloud altitude. These tests also suggest that, for conditions encompassing those sampled by the flight campaigns, the additional information contained within the far-infrared improves the algorithm’s performance compared to using mid-infrared data only. When the CIC is applied to the airborne radiance measurements, the classification performance of the algorithm is very high. However, in this case, the limited temporal and spatial variability in the measured spectra results in a less obvious advantage being apparent when using both mid- and far-infrared radiances compared to using mid-infrared information only. These results suggest that the CIC algorithm will be a useful addition to existing cloud classification tools but that further analyses of nadir radiance observations spanning the infrared and sampling a wider range of atmospheric and cloud conditions are required to fully probe its capabilities. This will be realised with the launch of the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission, ESA’s 9th Earth Explorer.
  • Journal article
    Kollmann, Cohen, Allen, Clark, Roussos, Vines, Dietrich, Wicht, de Pater, Runyon, Cartwright, Masters A, Brain, Hibbits, Mauk, Gkioulidou, Rymer, McNutt, Hue, Stanley, Brandtet al., 2020,

    Magnetospheric studies: a requirement for addressing interdisciplinary mysteries in the Ice Giant systems

    , Space Science Reviews, Vol: 216, ISSN: 0038-6308

    Uranus and Neptune are the least-explored planets in our Solar System. This paper summarizesmysteries about these incredibly intriguing planets and their environments spurred by our limitedobservations from Voyager 2 and Earth-based systems. Several of these observations are eitherinconsistent with our current understanding built from exploring other planetary systems, orindicate such unique characteristics of these Ice Giants that they leave us with more questions thananswers. This paper specifically focuses on the value of all aspects of magnetosphericmeasurements, from the radiation belt structure to plasma dynamics to coupling to the solar wind,through a future mission to either of these planets. Such measurements have large interdisciplinaryvalue, as demonstrated by the large number of mysteries discussed in this paper that cover othernon-magnetospheric disciplines, including planetary interiors, atmospheres, rings, and moons.
  • Journal article
    Wang S, Rashid T, Thorp H, Toumi Ret al., 2020,

    A shortening of the life-cycle of major tropical cyclones

    , Geophysical Research Letters, Vol: 47, Pages: 28 Jul 2020-28 Jul 2020, ISSN: 0094-8276

    In this study a comprehensive picture of the changing intensity life cycle of major (Category 3 and higher) tropical cyclones (TCs) is presented. Over the past decades, the lifetime maximum intensity has increased, but there has also been a significant decrease in duration of time spent at intensities greater than Category 1. These compensating effects have maintained a stable global mean‐accumulated cyclone energy of individual major TCs. The global mean duration of major TCs has shortened by about 1 day from 1982 to 2018. There has been both faster intensification (Categories 1 to 3) and weakening (Categories 3 to 1) by about 40%. The probabilities of rapid intensification and rapid weakening have both risen in the period 2000–2018 compared to 1982–1999. A statistically significant anticorrelation is found between the lifetime maximum intensity and the following duration of the final weakening. This suggests an element of self‐regulation of TC life cycles.
  • Journal article
    Archer MO, 2020,

    Space Sound Effects Short Film Festival: using the film festival model to inspire creative art–science and reach new audiences

    , Geoscience Communication, Vol: 3, Pages: 147-166, ISSN: 2569-7110

    The ultra-low frequency analogues of sound waves in Earth'smagnetosphere play a crucial role in space weather; however, the publicis largely unaware of this risk to our everyday lives and technology.As a way of potentially reaching new audiences, SSFX (Space Sound Effects) made 8 yearsof satellite wave recordings audible to the human ear with the aimof using it to create art. Partnering with film industry professionals,the standard processes of international film festivals were adoptedby the project in order to challenge independent filmmakers to incorporatethese sounds into short films in creative ways. Seven films coveringa wide array of topics and genres (despite coming from the same sounds)were selected for screening at a special film festival out of 22 submissions.The works have subsequently been shown at numerous established filmfestivals and screenings internationally. These events have attracteddiverse non-science audiences resulting in several unanticipated impacts on them, thereby demonstrating how working with the art world canopen up dialogues with both artists and audiences who would not ordinarily engage with science.
  • Journal article
    Madanian H, Schwartz SJ, Halekas JS, Wilson LBet al., 2020,

    Nonstationary Quasiperpendicular Shock and Ion Reflection at Mars

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 47, ISSN: 0094-8276
  • Journal article
    Vasko IY, Wang R, Mozer FS, Bale SD, Artemyev AVet al., 2020,

    On the Nature and Origin of Bipolar Electrostatic Structures in the Earth's Bow Shock

    , FRONTIERS IN PHYSICS, Vol: 8, ISSN: 2296-424X
  • Journal article
    Bandyopadhyay R, Sorriso-Valvo L, Chasapis A, Hellinger P, Matthaeus WH, Verdini A, Landi S, Franci L, Matteini L, Giles BL, Gershman DJ, Moore TE, Pollock CJ, Russell CT, Strangeway RJ, Torbert RB, Burch JLet al., 2020,

    In situ observation of hall magnetohydrodynamic cascade in space plasma

    , Physical Review Letters, Vol: 124, Pages: 225101 – 1-225101 – 7, ISSN: 0031-9007

    We present estimates of the turbulent energy-cascade rate derived from a Hall-magnetohydrodynamic (MHD) third-order law. We compute the contribution from the Hall term and the MHD term to the energy flux. Magnetospheric Multiscale (MMS) data accumulated in the magnetosheath and the solar wind are compared with previously established simulation results. Consistent with the simulations, we find that at large (MHD) scales, the MMS observations exhibit a clear inertial range dominated by the MHD flux. In the subion range, the cascade continues at a diminished level via the Hall term, and the change becomes more pronounced as the plasma beta increases. Additionally, the MHD contribution to interscale energy transfer remains important at smaller scales than previously thought. Possible reasons are offered for this unanticipated result.
  • Journal article
    Carnielli G, Galand M, Leblanc F, Modolo R, Beth A, Jia Xet al., 2020,

    Constraining Ganymede's neutral and plasma environments through simulations of its ionosphere and Galileo observations

    , Icarus, Vol: 343, Pages: 1-11, ISSN: 0019-1035

    Ganymede's neutral and plasma environments are poorly constrained by observations. Carnielli et al. (2019) developed the first 3D ionospheric model aimed at understanding the dynamics of the present ion species and at quantifying the presence of each component in the moon's magnetosphere. The model outputs were compared with Galileo measurements of the ion energy flux, ion bulk velocity and electron number density made during the G2 flyby. A good agreement was found in terms of ion energy distribution and bulk velocity, but not in terms of electron number density. In this work, we present some improvements to our model Carnielli et al. (2019) and quantitatively address the possible sources of the discrepancy found in the electron number density between the Galileo observations and our ionospheric model. We have improved the ion model by developing a collision scheme to simulate the charge-exchange interaction between the exosphere and the ionosphere. We have simulated the energetic component of the O$_2$ population, which is missing in the exospheric model of Leblanc et al. (2017) and added it to the original distribution, hence improving its description at high altitudes. These improvements are found to be insufficient to explain the discrepancy in the electron number density. We provide arguments that the input O$_2$ exosphere is underestimated and that the plasma production acts asymmetrically between the Jovian and anti-Jovian hemispheres. In particular, we estimate that the O$_2$ column density should be greater than $10^{15}$~cm$^{-2}$, i.e., higher than previously derived upper limits (and a factor 10 higher than the values from Leblanc et al. (2017)), and that the ionization frequency from electron impact must be higher in the anti-Jovian hemisphere for the G2 flyby conditions.
  • Journal article
    Yang L, Wang L, Zhao L, Tao J, Li G, Wimmer-Schweingruber RF, He J, Tian H, Bale SDet al., 2020,

    Quiet-time Solar Wind Suprathermal Electrons of Different Solar Origins

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 896, ISSN: 2041-8205

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