Publications

Journal article

Murray-Watson R, Gryspeerdt E, Goren T, 2023,

Investigating the development of clouds within marine cold air outbreaks

, Atmospheric Chemistry and Physics, Vol: 23, Pages: 9365-9383, ISSN: 1680-7316

Marine cold air outbreaks are important parts of the high-latitude climate system, and are characterised by strong surface fluxes generated by the air-sea temperature gradient. These fluxes promote cloud formation, which can be identified in satellite imagery by the distinct transformation of stratiform cloud ‘streets’ into a broken field of cumuliform clouds downwind of the outbreak. This evolution in cloud morphology changes the radiative properties of the cloud, and therefore is of importanceto the surface energy budget. While the drivers of stratocumulus-to-cumulus transitions, such as aerosols or the sea surface temperature gradient, have been extensively studied for subtropical clouds, the factors influencing transitions at higher latitudes are relatively poorly understood. This work uses reanalysis data to create a set of composite trajectories of cold air outbreaks moving off the Arctic ice edge and co-locates these trajectories with satellite data to generate a unique view of liquid-dominated cloud development within cold air outbreaks.The results of this analysis show that clouds embedded in cold-air outbreaks have distinctive properties relative to clouds following other trajectories in the region. The initial strength of the outbreak shows a lasting effect on cloud properties, with differences between clouds in strong and weak events visible over 30 hours after the air has left the ice edge. However, while the strength (measured by the magnitude of the marine cold-air outbreak index) of the outbreak affects the magnitude of cloud properties, it does not affect the timing of the transition to cumuliform clouds nor the top-of-atmosphere albedo. In contrast, the initial aerosol conditions do not strongly affect the magnitude of the cloud properties, but are correlated to cloud break-up,leading to an enhanced cooling effect in clouds moving through high aerosol conditions due to delayed break-up. Both the aerosol environment and the strength and

Journal article

Daei F, Pomoell J, Price DJ, Kumari A, Good S, Kilpua EKJet al., 2023,

Modeling the formation and eruption of coronal structures by linking data-driven magnetofrictional and MHD simulations for AR 12673⋆

, ASTRONOMY & ASTROPHYSICS, Vol: 676, ISSN: 0004-6361

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Citations: 1

Journal article

Horbury T, Bale S, mcmanus M, Larson D, Kasper J, Laker R, Matteini L, Raouafi N, Velli M, Woodham L, Woolley T, Fedorov A, Louarn P, Kieokaew R, Durovcova T, Chandran B, Owen Cet al., 2023,

Switchbacks, microstreams and broadband turbulence in the solar wind

, Physics of Plasmas, Vol: 30, ISSN: 1070-664X

Switchbacks are a striking phenomenon in near-Sun coronal hole flows, but their origins, evolution, and relation to the broadband fluctuations seen farther from the Sun are unclear. We use the near-radial lineup of Solar Orbiter and Parker Solar Probe during September 2020 when both spacecraft were in wind from the Sun's Southern polar coronal hole to investigate if switchback variability is related to large scale properties near 1 au⁠. Using the measured solar wind speed, we map measurements from both spacecraft to the source surface and consider variations with source Carrington longitude. The patch modulation of switchback amplitudes at Parker at 20 solar radii was associated with speed variations similar to microstreams and corresponds to solar longitudinal scales of around 5°–10°. Near 1 au⁠, this speed variation was absent, probably due to interactions between plasma at different speeds during their propagation. The alpha particle fraction, which has recently been shown to have spatial variability correlated with patches at 20 solar radii, varied on a similar scale at 1 au⁠. The switchback modulation scale of 5°–10°, corresponding to a temporal scale of several hours at Orbiter, was present as a variation in the average deflection of the field from the Parker spiral. While limited to only one stream, these results suggest that in coronal hole flows, switchback patches are related to microstreams, perhaps associated with supergranular boundaries or plumes. Patches of switchbacks appear to evolve into large scale fluctuations, which might be one driver of the ubiquitous turbulent fluctuations in the solar wind.

Journal article

Zazzeri G, Graven H, Xu X, Saboya E, Blyth L, Manning AJ, Chawner H, Wu D, Hammer Set al., 2023,

Radiocarbon measurements reveal underestimated fossil CH₄ and CO₂ emissions in London

, Geophysical Research Letters, Vol: 50, ISSN: 0094-8276

Radiocarbon (14C) is a powerful tracer of fossil emissions because fossil fuels are entirely depleted in 14C, but observations of 14CO2 and especially 14CH4 in urban regions are sparse. We present the first observations of 14C in both methane (CH4) and carbon dioxide (CO2) in an urban area (London) using a recently developed sampling system. We find that the fossil fraction of CH4 and the atmospheric concentration of fossil CO2 are consistently higher than simulated values using the atmospheric dispersion model NAME coupled with emission inventories. Observed net biospheric uptake in June–July is not well correlated with simulations using the SMURF model with NAME. The results show the partitioning of fossil and biospheric CO2 and CH4 in cities can be evaluated and improved with 14C observations when the nuclear power plants influence is negligible.

Journal article

Livi S, Lepri ST, Raines JM, Dewey RM, Galvin AB, Louarn P, Collier MR, Allegrini F, Alterman BL, Bert CM, Bruno R, Chornay DJ, D'Amicis R, Eddy TJ, Ellis L, Fauchon-Jones E, Fedorov A, Gershkovich I, Holmes J, Horbury TS, Kistler LM, Kucharek H, Lugaz N, Nieves-Chinchilla T, O'Brien H, Ogasawara K, Owen CJ, Phillips M, Ploof K, Rivera YJ, Spitzer SA, Stubbs TJ, Wurz Pet al., 2023,

First results from the Solar Orbiter Heavy Ion Sensor

, ASTRONOMY & ASTROPHYSICS, Vol: 676, ISSN: 0004-6361

Journal article

Heyns MJ, Lotz SI, Cilliers PJ, Gaunt CTet al., 2023,

Adaptations to a geomagnetic field interpolation method in Southern Africa

, ADVANCES IN SPACE RESEARCH, Vol: 72, Pages: 854-865, ISSN: 0273-1177

Journal article

Zhu X, He J, Duan D, Verscharen D, Owen CJ, Fedorov A, Louarn P, Horbury TSet al., 2023,

Non-field-aligned Proton Beams and Their Roles in the Growth of Fast Magnetosonic/Whistler Waves: Solar Orbiter Observations

, ASTROPHYSICAL JOURNAL, Vol: 953, ISSN: 0004-637X

Journal article

Zimbardo G, Ying B, Nisticò G, Feng L, Rodríguez-García L, Panasenco O, Andretta V, Banerjee D, Bemporad A, De Leo Y, Franci L, Frassati F, Habbal S, Long D, Magdalenic J, Mancuso S, Naletto G, Perri S, Romoli M, Spadaro D, Stangalini M, Strachan L, Susino R, Vainio R, Velli M, Cohen CMS, Giacalone J, Shen M, Telloni D, Abbo L, Burtovoi A, Jerse G, Landini F, Nicolini G, Pancrazzi M, Russano G, Sasso C, Uslenghi Met al., 2023,

A high-latitude coronal mass ejection observed by a constellation of coronagraphs: Solar Orbiter/Metis, STEREO-A/COR2, and SOHO/LASCO

, Astronomy and Astrophysics, Vol: 676, ISSN: 0004-6361

Context. A few days before the first perihelion of the Solar Orbiter nominal mission, which occurred on 2022 March 26, the Metis coronagraph on board Solar Orbiter detected a coronal mass ejection (CME) that was moving away from the far side of the Sun (with respect to Solar Orbiter) at high northern latitudes. The eruption was also seen by other spacecraft, in particular, by STEREO-A, which was in quadrature configuration with Solar Orbiter. Aims. We analyse the different views of the CME by a constellation of spacecraft with the purpose to determine the speed and acceleration of the CME, and to identify the source region of the CME. Methods. Considering the positions of various spacecraft on 2022 March 22, this CME happened to be within the field of view of STEREO-A/SECCHI, and it was visible over the limb from SOHO/LASCO. We present the results of the 3D reconstruction of the CME based on the graduated cylindrical shell model and of the identification of the possible origin of the CME using extreme-ultraviolet (EUV) observations by Solar Orbiter/EUI, STEREO-A/EUVI, and SDO/AIA. The observations in EUV are compared with the coronal magnetic structure obtained by the potential field source surface method. Results. The 3D reconstruction of the CME derives a central latitude of 29 N, a Stonyhurst longitude of 125, and an average radial speed at the apex of 322 ± 33 km s1 between 4 and 13 RȮ, which is probably not high enough to generate a shock wave. The estimated average acceleration of the CME is 16 ± 11 m s2 in the same range of distances from the Sun. This CME may be associated with the disappearance of a coronal cloud prominence, which is seen in the EUV by STEREO-A/EUVI and SDO/AIA, and is also associated with rapidly evolving emerging magnetic flux.

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Citations: 1

Journal article

Misal H, Varela E, Voulgarakis A, Rovithakis A, Grillakis M, Kountouris Yet al., 2023,

Assessing public preferences for a wildfire mitigation policy in Crete, Greece

, Forest Policy and Economics, Vol: 153, Pages: 1-16, ISSN: 1389-9341

The increased frequency and severity of wildfires in the Mediterranean region generates significant damages in ecosystems and landscapes while harming human populations. Institutional complexities, along with socioeconomic and demographic changes encouraging development into the wildland-urban interface, rural abandonment, and focus on fire suppression, are increasing the vulnerability and flammability of Mediterranean ecosystems. Developing effective strategies for managing wildfire incidence and its aftermath requires understanding of the public preferences for wildfire policy characteristics. Here we elicit public preferences for wildfire mitigation policies employing a stated choice experiment applied in Crete, Greece. A region with typical Mediterranean landscape experiencing significant development and rural-to-urban migration that disrupts existing fire regimes. We estimate conditional logit, mixed logit and latent class models to study the general public's preferences and willingness to pay for limiting wildfire frequency and agricultural land burnt, maintaining landscape features, and managing post-wildfire recovery. Results of our study show that measures to manage post-wildfire damage are consistently valued as the most positive amongst the sampled respondents, achieving values that range between €25.92 in conditional logit model to €46 in one of the latent classes identified. Improving the landscape quality follows in importance, although it shows more heterogeneity in the responses. The latent class approach allowed to identify that those associated with either the agricultural or the tourism sector of the sampled individuals, displayed significantly different preferences for the proposed attributes. Overall, our findings indicate that there is a strong preference amongst the general public to shift current policies based on suppression towards more integrated approaches dealing both with prevention and post-fire management. The outcomes of th

Journal article

Roberts OW, Voeroes Z, Torkar K, Stawarz J, Bandyopadhyay R, Gershman DJ, Narita Y, Kieokaew R, Lavraud B, Klein K, Yang Y, Nakamura R, Chasapis A, Matthaeus WHet al., 2023,

Estimation of the Error in the Calculation of the Pressure-Strain Term: Application in the Terrestrial Magnetosphere

, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 128, ISSN: 2169-9380

Journal article

Usanova ME, Ergun RE, Stawarz JE, 2023,

Ion Energization by Turbulent Electric Fields in Fast Earthward Flows and Its Implications for the Dynamics of the Inner Magnetosphere

, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 128, ISSN: 2169-9380

Journal article

Lewis HC, Stawarz JE, Franci L, Matteini L, Klein K, Salem CS, Burch JL, Ergun RE, Giles BL, Russell CT, Lindqvist P-Aet al., 2023,

Magnetospheric Multiscale measurements of turbulent electric fields in earth's magnetosheath: How do plasma conditions influence the balance of terms in generalized Ohm's law?

, PHYSICS OF PLASMAS, Vol: 30, ISSN: 1070-664X

Journal article

Vuorinen L, LaMoury AT, Hietala H, Koller Fet al., 2023,

Magnetosheath Jets Over Solar Cycle 24: An Empirical Model

, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 128, ISSN: 2169-9380

Journal article

Kilpua E, Vainio R, Cohen C, Dresing N, Good S, Ruohotie J, Trotta D, Bale SD, Christian E, Hill M, McComas DJ, McNutt R, Schwadron Net al., 2023,

Energetic ion enhancements in sheaths driven by interplanetary coronal mass ejections

, ASTROPHYSICS AND SPACE SCIENCE, Vol: 368, ISSN: 0004-640X

Journal article

Adhikari S, Shay M, Parashar T, Matthaeus W, Pyakurel P, Stawarz J, Eastwood Jet al., 2023,

Effect of a guide field on the turbulence like properties of magnetic reconnection

, Physics of Plasmas, Vol: 30, Pages: 1-14, ISSN: 1070-664X

The effect of an external guide field on the turbulence-like properties of magneticreconnection is studied using five different 2.5D kinetic particle-in-cell (PIC) simulations. The magnetic energy spectrum is found to exhibit a slope of approximately−5/3 in the inertial range, independent of the guide field. On the contrary, theelectric field spectrum, in the inertial range steepens more with the guide field andapproaches a slope of −5/3. In addition, spectral analysis of the different terms ofthe generalized Ohm’s law is performed and found to be consistent with PIC simulations of turbulence and MMS observations. Finally, the guide field effect on theenergy transfer behavior is examined using von-K´arm´an Howarth (vKH) equationbased on incompressible Hall-MHD. The general characteristics of the vKH equationwith constant rate of energy transfer in the inertial range, is consistent in all the simulations. This suggests that the qualitative behavior of energy spectrum, and energytransfer in reconnection is similar to that of turbulence, indicating that reconnectionfundamentally involves an energy cascade.

Journal article

Lewis ZM, Beth A, Altwegg K, Galand M, Goetz C, Heritier K, ORourke L, Rubin M, Stephenson Pet al., 2023,

Origin and trends in NH4+ observed in the coma of 67P

, Monthly Notices of the Royal Astronomical Society, Vol: 523, Pages: 6208-6219, ISSN: 0035-8711

The European Space Agency/Rosetta mission escorted comet 67P/Churyumov–Gerasimenko and witnessed the evolution of its coma from low activity (∼2.5–3.8 au) to rich ion-neutral chemistry (∼1.2–2.0 au). We present an analysis of the ion composition in the coma, focusing on the presence of protonated high proton affinity (HPA) species, in particular NH4+⁠. This ion is produced through the protonation of NH3 and is an indicator of the level of ion-neutral chemistry in the coma. We aim to assess the importance of this process compared with other NH4+ sources, such as the dissociation of ammonium salts embedded in dust grains. The analysis of NH4+ has been possible thanks to the high mass resolution of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Double Focusing Mass Spectrometer (ROSINA/DFMS). In this work, we examine the NH4+ data set alongside data from the Rosetta Plasma Consortium instruments, and against outputs from our in-house ionospheric model. We show that increased comet outgassing around perihelion yields more detections of NH4+ and other protonated HPA species, which results from more complex ion-neutral chemistry occurring in the coma. We also reveal a link between the low magnetic field strength associated with the diamagnetic cavity and higher NH4+ counts. This suggests that transport inside and outside the diamagnetic cavity is very different, which is consistent with 3D hybrid simulations of the coma: non-radial plasma dynamics outside the diamagnetic cavity is an important factor affecting the ion composition.

Journal article

Grimmich N, Plaschke F, Archer MO, Heyner D, Mieth JZD, Nakamura R, Sibeck DGet al., 2023,

Study of extreme magnetopause distortions under varying solar wind conditions

, JGR: Space Physics, Vol: 128, Pages: 1-22, ISSN: 2169-9402

To first order, the magnetopause (MP) is defined by a pressure balance between the solar wind and the magnetosphere. The boundary moves under the influence of varying solar wind conditions and transient foreshock phenomena, reaching unusually large and small distances from the Earth. We investigate under which solar wind conditions such extreme MP distortions occur. Therefore, we construct a database of magnetopause crossings (MPCs) observed by the THEMIS spacecraft in the years 2007 to mid-2022 using a simple Random Forest Classifier. Roughly 7% of the found crossing events deviate beyond reported errors in the stand-off distance from the Shue et al. (1998, https://doi.org/10.1029/98JA01103) MP model and thus are termed extreme distortions. We find the occurrence of these extreme events in terms of expansion or compression of the MP to be linked to different solar wind parameters, most notably to the IMF magnitude, cone angle, velocity, Alfvén Mach number and temperature. Foreshock transients like hot-flow anomalies and foreshock bubbles could be responsible for extreme magnetospheric expansions. The results should be incorporated into future magnetopause models and may be helpful for the reconstruction of the MP locations out of soft x-ray images, relevant for the upcoming SMILE mission.

Journal article

Chen L-J, Spence H, Klein K, Matthaeus W, Lavraud B, Szabo A, Roberts OW, Génot V, Verscharen D, Horbury T, Retino A, Alexandrova O, Reynolds C, Halekas J, Dors I, Arzamasskiy L, Contel OL, TenBarge J, Forsyth C, Jian L, Galvin A, Schekochihin A, Maruca BAet al., 2023,