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  • Journal article
    Trotta D, Vuorinen L, Hietala H, Horbury T, Dresing N, Gieseler J, Kouloumvakos A, Price D, Valentini F, Kilpua E, Vainio Ret al., 2022,

    Single-spacecraft techniques for shock parameters estimation: a systematic approach

    , Frontiers in Astronomy and Space Sciences, Vol: 9, Pages: 1-16, ISSN: 2296-987X

    Spacecraft missions provide the unique opportunity to study the properties of collisionless shocks utilising in situ measurements. In the past years, several diagnostics have been developed to address key shock parameters using time series of magnetic field (and plasma) data collected by a single spacecraft crossing a shock front. A critical aspect of such diagnostics is the averaging process involved in the evaluation of upstream/downstream quantities. In this work, we discuss several of these techniques, with a particular focus on the shock obliquity (defined as the angle between the upstream magnetic field and the shock normal vector) estimation. We introduce a systematic variation of the upstream/downstream averaging windows, yielding to an ensemble of shock parameters, which is a useful tool to address the robustness of their estimation. This approach is first tested with a synthetic shock dataset compliant with the Rankine-Hugoniot jump conditions for a shock, including the presence of noise and disturbances. We then employ self-consistent, hybrid kinetic shock simulations to apply the diagnostics to virtual spacecraft crossing the shock front at various stages of its evolution, highlighting the role of shock-induced fluctuations in the parameters’ estimation. This approach has the strong advantage of retaining some important properties of collisionless shock (such as, for example, the shock front microstructure) while being able to set a known, nominal set of shock parameters. Finally, two recent observations of interplanetary shocks from the Solar Orbiter spacecraft are presented, to demonstrate the use of this systematic approach to real events of shock crossings. The approach is also tested on an interplanetary shock measured by the four spacecraft of the Magnetospheric Multiscale (MMS) mission. All the Python software developed and used for the diagnostics (SerPyShock) is made available for the public, including an example of parameter estimation fo
  • Journal article
    Randich S, Gilmore G, Magrini L, Sacco GG, Jackson RJ, Jeffries RD, Worley CC, Hourihane A, Gonneau A, Vazquez CV, Franciosini E, Lewis JR, Alfaro EJ, Allende Prieto C, Bensby T, Blomme R, Bragaglia A, Flaccomio E, Francois P, Irwin MJ, Koposov SE, Korn AJ, Lanzafame AC, Pancino E, Recio-Blanco A, Smiljanic R, Van Eck S, Zwitter T, Asplund M, Bonifacio P, Feltzing S, Binney J, Drew J, Ferguson AMN, Micela G, Negueruela I, Prusti T, Rix H-W, Vallenari A, Bayo A, Bergemann M, Biazzo K, Carraro G, Casey AR, Damiani F, Frasca A, Heiter U, Hill V, Jofre P, de Laverny P, Lind K, Marconi G, Martayan C, Masseron T, Monaco L, Morbidelli L, Prisinzano L, Sbordone L, Sousa SG, Zaggia S, Adibekyan V, Bonito R, Caffau E, Daflon S, Feuillet DK, Gebran M, Gonzalez Hernandez J, Guiglion G, Herrero A, Lobel A, Maiz Apellaniz J, Montes D, Morel T, Soubiran C, Spina L, Tabernero HM, Traven G, Valentini M, Van der Swaelmen M, Villanova S, Wright NJ, Abbas U, Borsen-Koch VA, Alves J, Balaguer-Nunez L, Barklem PS, Barrado D, Berlanas SR, Binks AS, Bressan A, Capuzzo-Dolcetta R, Casagrande L, Casamiquela L, Collins RS, D'Orazi V, Dantas MLL, Debattista VP, Delgado-Mena E, Di Marcantonio P, Drazdauskas A, Evans NW, Famaey B, Franchini M, Fremat Y, Friel ED, Fu X, Geisler D, Gerhard O, Solares EAG, Grebel EK, Gutierrez Albarran ML, Hatzidimitriou D, Held E, Jimenez-Esteban F, Jonsson H, Jordi C, Khachaturyants T, Kordopatis G, Kos J, Lagarde N, Mahy L, Mapelli M, Marfil E, Martell SL, Messina S, Miglio A, Minchev I, Moitinho A, Montalban J, Monteiro MJPFG, Morossi C, Mowlavi N, Mucciarelli A, Murphy DNA, Nardetto N, Ortolani S, Paletou F, Palous J, Paunzen E, Pickering JC, Quirrenbach A, Fiorentin PR, Read J, Romano D, Ryde N, Sanna N, Santos W, Seabroke GM, Spagna A, Steinmetz M, Stonkute E, Sutorius E, Thevenin F, Tosi M, Tsantaki M, Vink JS, Wright N, Wyse RFG, Zoccali M, Zorec J, Zucker DB, Walton NAet al., 2022,

    The <i>Gaia</i>-ESO Public Spectroscopic Survey: Implementation, data products, open cluster survey, science, and legacy

    , ASTRONOMY & ASTROPHYSICS, Vol: 666, ISSN: 0004-6361
  • Journal article
    Gilmore G, Randich S, Worley CC, Hourihane A, Gonneau A, Sacco GG, Lewis JR, Magrini L, Francois P, Jeffries RD, Koposov SE, Bragaglia A, Alfaro EJ, Allende Prieto C, Blomme R, Korn AJ, Lanzafame AC, Pancino E, Recio-Blanco A, Smiljanic R, Van Eck S, Zwitter T, Bensby T, Flaccomio E, Irwin MJ, Franciosini E, Morbidelli L, Damiani F, Bonito R, Friel ED, Vink JS, Prisinzano L, Abbas U, Hatzidimitriou D, Held E, Jordi C, Paunzen E, Spagna A, Jackson RJ, Maiz Apellaniz J, Asplund M, Bonifacio P, Feltzing S, Binney J, Drew J, Ferguson AMN, Micela G, Negueruela I, Prusti T, Rix H-W, Vallenari A, Bergemann M, Casey AR, de Laverny P, Frasca A, Hill V, Lind K, Sbordone L, Sousa SG, Adibekyan V, Caffau E, Daflon S, Feuillet DK, Gebran M, Gonzalez Hernandez J, Guiglion G, Herrero A, Lobel A, Montes D, Morel T, Ruchti G, Soubiran C, Tabernero HM, Tautvaisiene G, Traven G, Valentini M, Van der Swaelmen M, Villanova S, Vazquez CV, Bayo A, Biazzo K, Carraro G, Edvardsson B, Heiter U, Jofre P, Marconi G, Martayan C, Masseron T, Monaco L, Walton NA, Zaggia S, Borsen-Koch VA, Alves J, Balaguer-Nunez L, Barklem PS, Barrado D, Bellazzini M, Berlanas SR, Binks AS, Bressan A, Capuzzo-Dolcetta R, Casagrande L, Casamiquela L, Collins RS, D'Orazi V, Dantas MLL, Debattista VP, Delgado-Mena E, Di Marcantonio P, Drazdauskas A, Evans NW, Famaey B, Franchini M, Fremat Y, Fu X, Geisler D, Gerhard O, Solares EAG, Grebel EK, Gutierrez Albarran ML, Jimenez-Esteban F, Jonsson H, Khachaturyants T, Kordopatis G, Kos J, Lagarde N, Ludwig H-G, Mahy L, Mapelli M, Marfil E, Martell SL, Messina S, Miglio A, Minchev I, Moitinho A, Montalban J, Monteiro MJPFG, Morossi C, Mowlavi N, Mucciarelli A, Murphy DNA, Nardetto N, Ortolani S, Paletou F, Palous J, Pickering JC, Quirrenbach A, Fiorentin PR, Read J, Romano D, Ryde N, Sanna N, Santos W, Seabroke GM, Spina L, Steinmetz M, Stonkute E, Sutorius E, Thevenin F, Tosi M, Tsantaki M, Wright N, Wyse RFG, Zoccali M, Zorec J, Zucker DBet al., 2022,

    The <i>Gaia</i>-ESO Public Spectroscopic Survey: Motivation, implementation, GIRAFFE data processing, analysis, and final data products☆

    , ASTRONOMY & ASTROPHYSICS, Vol: 666, ISSN: 0004-6361
  • Journal article
    Sparks N, Toumi R, 2022,

    The Dependence of Tropical Cyclone Pressure Tendency on Size

    , GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276
  • Journal article
    Bowen TA, Chandran BDG, Squire J, Bale SD, Duan D, Klein KG, Larson D, Mallet A, McManus MD, Meyrand R, Verniero JL, Woodham LDet al., 2022,

    In situ signature of cyclotron resonant heating in the solar wind

    , Physical Review Letters, Vol: 129, Pages: 1-8, ISSN: 0031-9007

    The dissipation of magnetized turbulence is an important paradigm for describing heating and energy transfer in astrophysical environments such as the solar corona and wind; however, the specific collisionless processes behind dissipation and heating remain relatively unconstrained by measurements. Remote sensing observations have suggested the presence of strong temperature anisotropy in the solar corona consistent with cyclotron resonant heating. In the solar wind, in situ magnetic field measurements reveal the presence of cyclotron waves, while measured ion velocity distribution functions have hinted at the active presence of cyclotron resonance. Here, we present Parker Solar Probe observations that connect the presence of ion-cyclotron waves directly to signatures of resonant damping in observed proton-velocity distributions using the framework of quasilinear theory. We show that the quasilinear evolution of the observed distribution functions should absorb the observed cyclotron wave population with a heating rate of 10−14  W/m3, indicating significant heating of the solar wind.
  • Journal article
    Watson-Parris D, Christensen MW, Laurenson A, Clewley D, Gryspeerdt E, Stier Pet al., 2022,

    Shipping regulations lead to large reduction in cloud perturbations.

    , Proceedings of the National Academy of Sciences of USA, Vol: 119, Pages: 1-5, ISSN: 0027-8424

    Global shipping accounts for 13% of global emissions of SO2, which, once oxidized to sulfate aerosol, acts to cool the planet both directly by scattering sunlight and indirectly by increasing the albedo of clouds. This cooling due to sulfate aerosol offsets some of the warming effect of greenhouse gasses and is the largest uncertainty in determining the change in the Earth's radiative balance by human activity. Ship tracks-the visible manifestation of the indirect of effect of ship emissions on clouds as quasi-linear features-have long provided an opportunity to quantify these effects. However, they have been arduous to catalog and typically studied only in particular regions for short periods of time. Using a machine-learning algorithm to automate their detection we catalog more than 1 million ship tracks to provide a global climatology. We use this to investigate the effect of stringent fuel regulations introduced by the International Maritime Organization in 2020 on their global prevalence since then, while accounting for the disruption in global commerce caused by COVID-19. We find a marked, but clearly nonlinear, decline in ship tracks globally: An 80% reduction in SO[Formula: see text] emissions causes only a 25% reduction in the number of tracks detected.
  • Journal article
    Kourgialas NN, Hliaoutakis A, Argyriou A, Morianou G, Voulgarakis AE, Kokinou E, Daliakopoulos IN, Kalderis D, Tzerakis K, Psarras G, Papadopoulos N, Manios T, Vafidis A, Soupios Pet al., 2022,

    A web-based GIS platform supporting innovative irrigation management techniques at farm-scale for the Mediterranean island of Crete

    , SCIENCE OF THE TOTAL ENVIRONMENT, Vol: 842, ISSN: 0048-9697
  • Journal article
    Laker R, Horbury TS, Matteini L, Bale SD, Stawarz JE, Woodham LD, Woolley Tet al., 2022,

    Switchback deflections beyond the early parker solar probe encounters

    , Monthly Notices of the Royal Astronomical Society, Vol: 517, Pages: 1001-1005, ISSN: 0035-8711

    Switchbacks are Aflvénic fluctuations in the solar wind, which exhibit large rotations in the magnetic field direction. Observations from Parker Solar Probe’s (PSP’s) first two solar encounters have formed the basis for many of the described switchback properties and generation mechanisms. However, this early data may not be representative of the typical near-Sun solar wind, biasing our current understanding of these phenomena. One defining switchback property is the magnetic deflection direction. During the first solar encounter, this was primarily in the tangential direction for the longest switchbacks, which has since been discussed as evidence, and a testable prediction, of several switchback generation methods. In this study, we re-examine the deflection direction of switchbacks during the first eight PSP encounters to confirm the existence of a systematic deflection direction. We first identify switchbacks exceeding a threshold deflection in the magnetic field and confirm a previous finding that they are arc-polarized. In agreement with earlier results from PSP’s first encounter, we find that groups of longer switchbacks tend to deflect in the same direction for several hours. However, in contrast to earlier studies, we find that there is no unique direction for these deflections, although several solar encounters showed a non-uniform distribution in deflection direction with a slight preference for the tangential direction. This result suggests a systematic magnetic configuration for switchback generation, which is consistent with interchange reconnection as a source mechanism, although this new evidence does not rule out other mechanisms, such as the expansion of wave modes.
  • Journal article
    Telloni D, Adhikari L, Zank GP, Hadid LZ, Sanchez-Cano B, Sorriso-Valvo L, Zhao L, Panasenco O, Shi C, Velli M, Susino R, Verscharen D, Milillo A, Alberti T, Narita Y, Verdini A, Grimani C, Bruno R, D'Amicis R, Perrone D, Marino R, Carbone F, Califano F, Malara F, Stawarz JE, Laker R, Liberatore A, Bale SD, Kasper JC, Heyner D, de Wit TD, Goetz K, Harvey PR, MacDowall RJ, Malaspina DM, Pulupa M, Case AW, Korreck KE, Larson D, Livi R, Stevens ML, Whittlesey P, Auster H-U, Richter Iet al., 2022,

    Observation and Modeling of the Solar Wind Turbulence Evolution in the Sub-Mercury Inner Heliosphere

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 938, ISSN: 2041-8205
  • Journal article
    Montagud-Camps V, Hellinger P, Verdini A, Papini E, Franci L, Landi Set al., 2022,

    Quantification of the Cross-helicity Turbulent Cascade in Compressible MHD Simulations

    , ASTROPHYSICAL JOURNAL, Vol: 938, ISSN: 0004-637X
  • Journal article
    Badman ST, Carley E, Canizares LA, Dresing N, Jian LK, Lario D, Gallagher PT, Martinez Oliveros JC, Pulupa M, Bale SDet al., 2022,

    Tracking a Beam of Electrons from the Low Solar Corona into Interplanetary Space with the Low Frequency Array, Parker Solar Probe, and 1 au Spacecraft

    , ASTROPHYSICAL JOURNAL, Vol: 938, ISSN: 0004-637X
  • Journal article
    Sparks N, Toumi R, 2022,

    A physical model of tropical cyclone central pressure filling at landfall

    , Journal of the Atmospheric Sciences, Vol: 79, Pages: 2585-2599, ISSN: 0022-4928

    We derive a simple physically based analytic model which describes the pressure filling of a tropical cyclone (TC) over land. Starting from the axisymmetric mass continuity equation in cylindrical coordinates we derive that the half-life decay of the pressure deficit between the environmentand TC centre is proportional to the initial radius of maximum surface wind speed. The initial pressure deficit and column-mean radial inflow speed into the core are the other key variables. The assumptions made in deriving the model are validated against idealised numerical simulations of TC decay over land. Decay half-lives predicted from a range of initial TC states are tested against the idealized simulations and are in good agreement. Dry idealised TC decay simulations show that without latent convective heating, the boundary layer decouples from the vortex above leading to a fast decay of surface winds while a mid-level vortex persists.
  • Journal article
    Zhao J, Malaspina DM, de Wit TD, Pierrard V, Voitenko Y, Lapenta G, Poedts S, Bale SD, Kasper JC, Larson D, Livi R, Whittlesey Pet al., 2022,

    Broadband Electrostatic Waves near the Lower-hybrid Frequency in the Near-Sun Solar Wind Observed by the Parker Solar Probe

    , ASTROPHYSICAL JOURNAL LETTERS, Vol: 938, ISSN: 2041-8205
  • Journal article
    Owen CJ, Abraham JB, Nicolaou G, Verscharen D, Louarn P, Horbury TSet al., 2022,

    Solar Orbiter SWA Observations of Electron Strahl Properties Inside 1 AU

    , UNIVERSE, Vol: 8
  • Journal article
    Schwartz SJ, Goodrich KA, Wilson LB, Turner DL, Trattner KJ, Kucharek H, Gingell I, Fuselier SA, Cohen IJ, Madanian H, Ergun RE, Gershman DJ, Strangeway RJet al., 2022,

    Energy Partition at Collisionless Supercritical Quasi-Perpendicular Shocks

    , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380
  • Journal article
    Brandt PC, Provornikova EA, Cocoros A, Turner D, DeMajistre R, Runyon K, Lisse CM, Bale S, Kurth WS, Galli A, Wurz P, McNutt RL, Wimmer-Schweingruber R, Linsky J, Redfield S, Kollmann P, Mandt KE, Rymer AM, Roelof EC, Kinnison J, Opher M, Hill ME, Paul Met al., 2022,

    Interstellar Probe: Humanity?s exploration of the Galaxy Begins

    , ACTA ASTRONAUTICA, Vol: 199, Pages: 364-373, ISSN: 0094-5765
  • Journal article
    Wells CD, Kasoar M, Bellouin N, Voulgarakis Aet al., 2022,

    Supplementary material to "Local and remote climate impacts of future African aerosol emissions"
  • Journal article
    Agiwal O, Moore L, Martinis C, Mueller-Wodarg I, Huba Jet al., 2022,

    First Steps Towards a New Saturn Ionosphere Model Including Ring-Planet Coupling and Electrodynamics

    <jats:p>&amp;lt;div&amp;gt;&amp;lt;div&amp;gt;&amp;lt;div&amp;gt;&amp;lt;div&amp;gt;The Cassini Grand Finale revealed that there is still much that we do not understand about Saturn&amp;amp;#8217;s upper atmosphere. In-situ observations reveal highly complex coupling between the planetary atmosphere and rings and inter-hemispheric electrodynamic coupling at latitudes that are magnetically connected to the intra D-ring region in the magnetosphere. Current Saturn models are ill-suited to treating electrodynamics and ring-planet interactions at Saturn. Thus, we adapt SAMI, a well-known terrestrial ionosphere model that is flux-tube based and already includes electrodynamics, to Saturn, with the aim of using it in conjunction with existing Saturn models such as the STIM-GCM (Saturn Thermosphere Ionosphere Model) to decipher the long-standing unexplained morphologies in Saturn&amp;amp;#8217;s ionosphere and investigate the ring-atmosphere coupling and electrodynamics revealed by the Cassini end-of-mission data. We will present initial results having adapted SAMI to Saturn, showing the full extent of the atmospheric chemistry and model capabilities at present. We will discuss future directions of development towards the construction of the new model capable of resolving the complex ring-atmosphere coupling and electrodynamics, and the possibility of adapting this model to other planets.&amp;lt;/div&amp;gt;&amp;lt;/div&amp;gt;&amp;lt;/div&amp;gt;&amp;lt;/div&amp;gt;</jats:p>
  • Journal article
    Kaweeyanun N, Masters A, 2022,

    Can Ganymede's magnetopause help us probe its subsurface ocean?
  • Journal article
    Grant S, Jones G, Owen C, Matteini Let al., 2022,

    The Prediction of, and Results from Solar Orbiter's encounter with Comet C/2021 A1 (Leonard).

    <jats:p>&amp;lt;p&amp;gt;As the solar wind encounters a comet, ionized gas released from the nucleus propagates away from the Sun with the wind, forming the ion tail of the comet that can stretch for multiple astronomical units. The transport of cometary material antisunward of the comet provides opportunities to measure the cometary composition and plasma interactions at a significant distance from a comet&amp;amp;#8217;s nucleus. Serendipitous crossings by spacecraft of comets&amp;amp;#8217; ion tails is a surprisingly commonplace occurrence, but can go unnoticed, as any measured plasma fluctuations can be small.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Using the measured flow of the solar wind at the spacecraft, we can estimate the motion of the solar plasma upstream of the spacecraft, and compare this trajectory with the locations of known comets. This method can uncover previously unnoticed ion tail encounters and predict future encounters.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;In December 2021, while comet C/2021 A1 (Leonard) traversed the ecliptic plane, sunward of the spacecraft Solar Orbiter, the spacecraft was immersed in the comet&amp;amp;#8217;s ion tail. This encounter was predicted using a range of estimated solar wind velocities to estimate the motion of solar wind plasma to the spacecraft. A wealth of data was collected during the encounter, including results from multiple instruments that support the prediction. We present data returned from the SWA and magnetometer instruments, providing information on the structure of the induced magnetotail. Additionally, images of comet Leonard&amp;amp;#8217;s ion tail from other spacecraft during the encounter provide a uniquely complete picture of the tail crossing.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;em&amp;gt;Fig: Orbital configuration of comet Leonard and Sola
  • Conference paper
    Stephenson P, Galand M, Deca J, Henri Pet al., 2022,

    Cold electrons at a weakly outgassing comet

    , Europlanet Science Congress 2022, Publisher: Copernicus GmbH
  • Journal article
    Dipu S, Schwarz M, Ekman AML, Gryspeerdt E, Goren T, Sourdeval O, Mulmenstadt J, Quaas Jet al., 2022,

    Exploring satellite-derived relationships between cloud droplet number concentration and liquid water path using a large- domain large-eddy simulation

    , Tellus Series B: Chemical and Physical Meteorology, Vol: 74, Pages: 176-188, ISSN: 0280-6509

    Important aspects of the adjustments to aerosol-cloud interactions can be examined using the relationship between cloud droplet number concentration (Nd) 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 Nd 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 Nd, we have also considered adiabatic Nd (NAd) from the LES model for comparison. The joint histogram analysis shows that the NAd-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 NAd and LWP; the corresponding mean LWP (LWP) shows a weak relation with NAd. The CP shows a larger spread at higher NAd (>50 cm–3), and the LWP increases non-monotonically with increasing NAd in both cases. Nevertheless, both lack the negative NAd-LWP relationship at higher NAd, the entrainment effect on cloud droplets. In contrast, the model simulated Nd-LWP clearly illustrates a much more nonlinear (an increase in LWP with increasing Nd and a decrease in LWP at higher Nd) relationship, which clearly depicts the cloud lifetime and the entrainment effect. Additionally, our analysis demonstrates a regime dependency (marine and continental) in the NAd-LWP relation from the satellite retrievals. Comparing local vs large-scale statistics from satellite data shows that continental clouds exhibit only a weak nonlinear NAd-LWP relationship. Hence a regime-based Nd-LWP analysis is even more relevant when it comes to warm continental clouds and their comparison to satellite retrievals.
  • Journal article
    Buitrago-Casas JC, Glesener L, Christe S, Krucker S, Vievering J, Athiray PS, Musset S, Davis L, Courtade S, Dalton G, Turin P, Turin Z, Ramsey B, Bongiorno S, Ryan D, Takahashi T, Furukawa K, Watanabe S, Narukage N, Ishikawa S-N, Mitsuishi I, Hagino K, Van S, Duncan J, Zhang Y, Bale SDet al., 2022,

    The faintest solar coronal hard X-rays observed with FOXSI

    , ASTRONOMY & ASTROPHYSICS, Vol: 665, ISSN: 0004-6361
  • Journal article
    Gryspeerdt E, Glassmeier F, Feingold G, Hoffmann F, Murray-Watson Ret al., 2022,

    Observing short timescale cloud development to constrain aerosol-cloud interactions

    , Atmospheric Chemistry and Physics, Vol: 22, Pages: 11727-11738, ISSN: 1680-7316

    The aerosol impact on liquid water path (LWP) is a key uncertainty in the overall climate impact of aerosol. However, despite a significant effort in this area, the size of the effect remains poorly constrained, and even the sign is unclear. Recent studies have shown that the relationship between droplet number concentration (Nd ) and LWP is an unreliable measure of theimpact of Nd variations on LWP due to the difficulty in establishing causality. In this work, we use satellite observations of the short-term development of clouds to examine the role of Nd perturbations in LWP variations. Similar to previous studies, an increase followed by a general decrease in LWP with increasing Nd is observed, suggesting an overall negative LWP response to Nd and a warming LWP adjustment to aerosol. However, the Nd also responds to the local environment, with aerosol production, entrainment from the free troposphere and wet scavenging all acting to modify the Nd . Many of these effects act to further steepen the Nd -LWP relationship and obscure the causal Nd impact on LWP. Using the temporal development of clouds to account for these feedbacks in the Nd -LWP system, a weaker negative Nd -LWP relationship is observed over most of the globe. This relationship is highly sensitive to the initial cloud state, illuminating the roles of different processes in shaping the Nd -LWP relationship. The nature of the current observing system limits this work toa single time period for observations, highlighting the need for more frequent observations of key cloud properties to constrain cloud behaviour at process timescales.
  • Journal article
    Corti C, Whitman K, Desai R, Rankin J, Strauss DT, Nitta N, Turner D, Chen TYet al., 2022,

    Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space: Need for contextual energetic particle measurements at Earth and supporting distributed observations

    , White Paper submitted to Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033
  • Journal article
    Ruohotie J, Kilpua EKJ, Good SW, Ala-Lahti Met al., 2022,

    Small-scale flux ropes in ICME sheaths

    , FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 9, ISSN: 2296-987X
  • Journal article
    Eggington J, Coxon J, Shore R, Desai R, Mejnertsen L, Chittenden J, Eastwood Jet al., 2022,

    Response timescales of the magnetotail current sheet during a geomagnetic storm: global MHD simulations

    , Frontiers in Astronomy and Space Sciences, Vol: 9, Pages: 1-17, ISSN: 2296-987X

    The response of the Earth’s magnetotail current sheet to the external solar wind driver is highly time-dependent and asymmetric. For example, the current sheet twists in response to variations in the By component of the interplanetary magnetic field (IMF), and is hinged by the dipole tilt. Understanding the timescales over which these asymmetries manifest is of particular importance during geomagnetic storms when the dynamics of the tail control substorm activity. To investigate this, we use the Gorgon MHD model to simulate a geomagnetic storm which commenced on 3 May 2014, and was host to multiple By and Bz reversals and a prolonged period of southward IMF driving. We find that the twisting of the current sheet is well-correlated to IMF By throughout the event, with the angle of rotation increasing linearly with downtail distance and being morepronounced when the tail contains less open flux. During periods of southward IMF the twisting of the central current sheet responds most strongly at a timelag of ∼ 100 min for distances beyond 20 RE, consistent with the 1-2 hr convection timescale identified in the open flux content. Under predominantly northward IMF the response of the twisting is bimodal, with the strongest correlations between 15-40 RE downtail being at a shorter timescale of ∼ 30 min consistent with that estimated for induced By due to wave propagation, compared to a longer timescale of ∼ 3 hr further downtail again attributed to convection. This indicates that asymmetries in the magnetotail communicated by IMF By are influenced mostly by global convection during strong solar wind driving, but that more prompt induced By effects can dominate in the near-Earth tail and during periods of weaker driving. These results provide new insight into the characteristic timescales of solar wind-magnetosphere-ionosphere coupling.
  • Journal article
    Nair R, Halekas JS, Whittlesey PL, Larson DE, Livi R, Berthomier M, Kasper JC, Case AW, Stevens ML, Bale SD, MacDowall RJ, Pulupa MPet al., 2022,

    Switchbacks in the Young Solar Wind: Electron Evolution Observed inside Switchbacks between 0.125 au and 0.25 au

    , ASTROPHYSICAL JOURNAL, Vol: 936, ISSN: 0004-637X
  • Conference paper
    Stephenson P, Altwegg K, Beth A, Burch J, Carr C, Deca J, Eriksson A, Galand M, Glassmeier K-H, Goetz C, Henri P, Heritier K, Johansson F, Lewis Z, Nilsson H, Rubin Met al., 2022,

    The source of electrons at a weakly outgassing comet

    , Publisher: Copernicus GmbH

    <jats:p>&amp;lt;p&amp;gt;The Rosetta spacecraft escorted comet 67P/Churyumov-Gerasimenko for two years along its orbit, from Aug 2014 to Sep 2016, observing the evolution of the comet from a close perspective. The Rosetta Plasma Consortium (RPC) monitored the plasma environment at the spacecraft throughout the escort phase.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Cometary electrons are produced by ionization of the neutral gas coma. This occurs through photoionization by extreme ultraviolet photons, and through electron-impact ionization (EII) by collisions of energetic electrons with the coma. Far from perihelion, EII is, at times, more prevalent than photoionization (Galand et al., 2016; Heritier et al., 2018), but the EII frequency has not been assessed across the whole mission. The source of the cometary electrons, and the origin of the ionizing electrons is still unclear.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We have calculated the electron impact ionization (EII) frequency throughout the Rosetta mission and at its location from measurements of RPC&amp;amp;#8217;s Ion and Electron Sensor (RPC/IES). EII ionization is confirmed as the dominant source of cometary electrons and ions when far from perihelion but is much more variable than photoionization. We compare the EII frequency with properties of the neutral coma and cometary plasma to identify key drivers of the energetic electron population. The EII frequency is structured by outgassing rate and magnetic field strength.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The first 3D collision model of electrons at a comet (Stephenson et al. 2022) is also utilised to assess the origin of electrons within the coma. The model uses self-consistently calculated electric and magnetic fields from a fully-kinetic and collisionless Particle-in-Cell model (Deca et al. 2017, 2019)as an input. The modelling approach confirms cometary electrons are produced by impacts of energetic e
  • Conference paper
    Lewis Z, Beth A, Altwegg K, Eriksson A, Galand M, Götz C, Henri P, Héritier K, O'Rourke L, Richter I, Rubin M, Stephenson P, Vallieres Xet al., 2022,

    Ionospheric composition of comet 67P near perihelion with multi-instrument Rosetta datasets

    , Publisher: Copernicus GmbH

    <jats:p>&amp;lt;p&amp;gt;The European Space Agency Rosetta mission escorted comet 67P/Churyumov-Gerasimenko for two years, during which it acquired an extensive dataset, revealing unprecedented detail about the neutral and plasma environment of the coma. The measurements were made over a large range of heliocentric distances, and therefore of outgassing activities, as Rosetta witnessed 67P evolve from a low-activity icy body at 3.8 AU to a dynamic object with large-scale plasma structures and rich ion and neutral chemistry near perihelion at 1.2 AU. One such plasma structure is the diamagnetic cavity, a region of negligible magnetic field surrounding the comet nucleus. It is formed through the interaction of the unmagnetized outwardly expanding cometary plasma with the incoming solar wind. This region was encountered many times by Rosetta between April 2015 and February 2016, as the comet moved towards and away from perihelion.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;In this study, we focus on the changing role of chemistry during the escort phase, particularly on trends in the detection of high proton affinity species near perihelion and within the diamagnetic cavity. NH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt; is produced through the protonation of NH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; which has the highest proton affinity of the neutral species and is therefore the terminal ion. The ratio of this species to the major ion species H&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;O&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt; can then be an indicator of the importance of ion-neutral chemistry as an ion loss process compared to transport. We use data from the high resolution mode of the ROSINA (Rosetta Orbital Spectrometer for Ion-Neutral Analysis)/DFMS (Double Focussing Mass Spectrometer) instrument, which allows certain ions of the

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