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Journal articlePage B, Vasko IY, Artemyev A, et al., 2021, , ASTROPHYSICAL JOURNAL LETTERS, Vol: 919, ISSN: 2041-8205
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- Citations: 16
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Journal articleMitchell JG, De Nolfo GA, Hill ME, et al., 2021, , ASTROPHYSICAL JOURNAL, Vol: 919, ISSN: 0004-637X
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- Citations: 23
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Journal articleFowler CM, Hanley KG, McFadden JP, et al., 2021, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380
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- Citations: 7
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Journal articleTelloni D, Andretta V, Antonucci E, et al., 2021, , The Astrophysical Journal Letters, Vol: 920, Pages: L14-L14
This Letter addresses the first Solar Orbiter (SO)–Parker Solar Probe (PSP) quadrature, occurring on 2021 January 18 to investigate the evolution of solar wind from the extended corona to the inner heliosphere. Assuming ballistic propagation, the same plasma volume observed remotely in the corona at altitudes between 3.5 and 6.3 solar radii above the solar limb with the Metis coronagraph on SO can be tracked to PSP, orbiting at 0.1 au, thus allowing the local properties of the solar wind to be linked to the coronal source region from where it originated. Thanks to the close approach of PSP to the Sun and the simultaneous Metis observation of the solar corona, the flow-aligned magnetic field and the bulk kinetic energy flux density can be empirically inferred along the coronal current sheet with an unprecedented accuracy, allowing in particular estimation of the Alfvén radius at 8.7 solar radii during the time of this event. This is thus the very first study of the same solar wind plasma as it expands from the sub-Alfvénic solar corona to just above the Alfvén surface.
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Journal articleArridge CS, Eggington JWB, 2021, , ICARUS, Vol: 367, ISSN: 0019-1035
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- Citations: 22
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Journal articleRymer AM, Runyon KD, Clyde B, et al., 2021, , PLANETARY SCIENCE JOURNAL, Vol: 2
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- Citations: 15
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Journal articleFargette N, Lavraud B, Rouillard AP, et al., 2021, , ASTROPHYSICAL JOURNAL, Vol: 919, ISSN: 0004-637X
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- Citations: 64
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Journal articlePusack A, Malaspina DM, Szalay JR, et al., 2021, , PLANETARY SCIENCE JOURNAL, Vol: 2
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- Citations: 22
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Journal articleSzalay JR, Pokorny P, Malaspina DM, et al., 2021, , PLANETARY SCIENCE JOURNAL, Vol: 2
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- Citations: 30
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Journal articleMoore KMM, Bolton B, Cao H, et al., 2021, , PLANETARY SCIENCE JOURNAL, Vol: 2
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- Citations: 2
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Journal articleZomerdijk-Russell S, Masters A, Heyner D, 2021, , Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-15, ISSN: 2169-9380
Mercury’s magnetosphere is a unique and dynamic system, primarily due to the proximity of the planet to the Sun and its small size. Interactions between solar wind and embedded Interplanetary Magnetic Field (IMF) and the dayside Hermean magnetosphere drive an electric current on the system’s magnetopause boundary. So far, electromagnetic induction due to magnetopause motion in response to changing external pressure has been used to constrain Mercury’s iron core size. Here we assess the impact a changing IMF direction has on the Hermean magnetopause currents, and the resulting inducing magnetic field. Observations made by MESSENGER during dayside magnetopause boundary crossings in the first ‘hot season’, are used to demonstrate the importance of the IMF direction to Mercury’s magnetopause currents. Our 16 boundary crossings show that introduction of external IMFs change the magnetopause current direction by 10° to 100°, compared to the case where only the internal planetary field is considered. Analytical modelling was used to fill in the bigger picture and suggests for an east-west reversal of the IMF, typical of the heliospheric current 3 sheet sweeping over Mercury’s magnetosphere, the inducing field at Mercury’s surface caused by the resulting magnetopause current dynamics is on the order of 30% of the global planetary field. These results suggest that IMF variability alone has an appreciable effect on Mercury’s magnetopause current and generates a significant inducing magnetic field around the planet. The arrival of the BepiColombo mission will allow this response to be further explored as a method of probing Mercury’s interior.
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Journal articleDesai R, Eastwood J, Horne R, et al., 2021, , Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-14, ISSN: 2169-9380
Energetic particle fluxes in the outer magnetosphere present a significant challenge to modellingefforts as they can vary by orders of magnitude in response to solar wind driving conditions. In thisarticle, we demonstrate the ability to propagate test particles through global MHD simulations to ahigh level of precision and use this to map the cross-field radial transport associated with relativisticelectrons undergoing drift orbit bifurcations (DOBs). The simulations predict DOBs primarily occurwithin an Earth radius of the magnetopause loss cone and appears significantly different for southwardand northward interplanetary magnetic field orientations. The changes to the second invariant areshown to manifest as a dropout in particle fluxes with pitch angles close to 90鈼nd indicate DOBsare a cause of butterfly pitch angle distributions within the night-time sector. The convective electricfield, not included in previous DOB studies, is found to have a significant effect on the resultant longterm transport, and losses to the magnetopause and atmosphere are identified as a potential methodfor incorporating DOBs within Fokker-Planck transport models.
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Journal articleLario D, Richardson IG, Palmerio E, et al., 2021, , ASTROPHYSICAL JOURNAL, Vol: 920, ISSN: 0004-637X
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- Citations: 15
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Journal articleVerscharen D, Bale SD, Velli M, 2021, , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 506, Pages: 4993-5004, ISSN: 0035-8711
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- Citations: 20
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Journal articleGingell I, Schwartz SJ, Kucharek H, et al., 2021, , PHYSICS OF PLASMAS, Vol: 28, ISSN: 1070-664X
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- Citations: 6
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Journal articleSalvi P, Ceppi P, Gregory JM, 2021, , Geophysical Research Letters, Vol: 48, ISSN: 0094-8276
Effective radiative forcing includes a contribution by rapid adjustments, that is, changes in temperature, water vapor, and clouds that modify the energy budget. Cloud adjustments in particular have been shown to depend strongly on forcing agent. We perform idealized atmospheric heating experiments to demonstrate a relationship between cloud adjustment and the vertical profile of imposed radiative heating: boundary-layer heating causes a positive cloud adjustment (a net downward radiative anomaly), while free-tropospheric heating yields a negative adjustment. This dependence is dominated by the shortwave effect of changes in low clouds. Much of the variation in cloud adjustment among common forcing agents such as CO2, CH4, solar forcing, and black carbon is explained by the “characteristic altitude” (i.e., the vertical center-of-mass) of their heating profiles, through its effect on tropospheric stability.
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Journal articleTang T, Shindell D, Zhang Y, et al., 2021, , Atmospheric Chemistry and Physics, Vol: 21, Pages: 13797-13809, ISSN: 1680-7316
For the radiative impact of individual climate forcings, most previous studies focused on the global mean values at the top of the atmosphere (TOA), and less attention has been paid to surface processes, especially for black carbon (BC) aerosols. In this study, the surface radiative responses to five different forcing agents were analyzed by using idealized model simulations. Our analyses reveal that for greenhouse gases, solar irradiance, and scattering aerosols, the surface temperature changes are mainly dictated by the changes of surface radiative heating, but for BC, surface energy redistribution between different components plays a more crucial role. Globally, when a unit BC forcing is imposed at TOA, the net shortwave radiation at the surface decreases by −5.87±0.67 W m−2 (W m−2)−1 (averaged over global land without Antarctica), which is partially offset by increased downward longwave radiation (2.32±0.38 W m−2 (W m−2)−1 from the warmer atmosphere, causing a net decrease in the incoming downward surface radiation of −3.56±0.60 W m−2 (W m−2)−1. Despite a reduction in the downward radiation energy, the surface air temperature still increases by 0.25±0.08 K because of less efficient energy dissipation, manifested by reduced surface sensible (−2.88±0.43 W m−2 (W m−2)−1) and latent heat flux (−1.54±0.27 W m−2 (W m−2)−1), as well as a decrease in Bowen ratio (−0.20±0.07 (W m−2)−1). Such reductions of turbulent fluxes can be largely explained by enhanced air stability (0.07±0.02 K (W m−2)−1), measured as the difference of the potential temperature between 925 hPa and surface, and reduc
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Journal articleHadid LZ, Genot V, Aizawa S, et al., 2021, , FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, Vol: 8, ISSN: 2296-987X
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- Citations: 14
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Journal articlePalchetti L, Brindley H, Bantges R, et al., 2021, , Bulletin of the American Meteorological Society, Vol: 102, Pages: 851-855, ISSN: 0003-0007
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- Citations: 1
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Journal articleVuorinen L, Hietala H, Plaschke F, et al., 2021, , Journal of Geophysical Research: Space Physics, Vol: 126, ISSN: 2169-9380
Magnetosheath jets travel from the bow shock toward the magnetopause, and some of them eventually impact it. Jet impacts have recently been linked to triggering magnetopause reconnection in case studies by Hietala et al. (2018, https://doi.org/10.1002/2017gl076525) and Nykyri et al. (2019, https://doi.org/10.1029/2018ja026357). In this study, we focus on the enhancing or suppressing effect jets could have on reconnection by locally altering the magnetic shear via their own magnetic fields. Using observations from the years 2008–2011 made by the Time History of Events and Macroscale Interactions during Substorms spacecraft and solar wind OMNI data, we statistically study for the first time urn:x-wiley:21699380:media:jgra56695:jgra56695-math-0002 within jets in the Geocentric Solar Magnetospheric coordinates. We find that urn:x-wiley:21699380:media:jgra56695:jgra56695-math-0003 opposite to the prevailing interplanetary magnetic field (IMF) urn:x-wiley:21699380:media:jgra56695:jgra56695-math-0004 is roughly as common in jets as in the non-jet magnetosheath near the magnetopause, but these observations are distributed differently. 60–70% of jet intervals contain bursts of opposite polarity urn:x-wiley:21699380:media:jgra56695:jgra56695-math-0005 in comparison to around 40urn:x-wiley:21699380:media:jgra56695:jgra56695-math-0006 of similar non-jet intervals. The median duration of such a burst in jets is 10 s and strength is urn:x-wiley:21699380:media:jgra56695:jgra56695-math-0007nT. We also investigate the prevalence of the type of strong urn:x-wiley:21699380:media:jgra56695:jgra56695-math-0008nT pulses that Nykyri et al. (2019, https://doi.org/10.1029/2018ja026357) linked to a substorm onset. In our data set, such pulses were observed in around 13% of jets. Our statistical results indicate that jets may have the potential to affect local magnetopause reconnection via their magnetic fields. Future studies are needed to determine whether such effects can be ob
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Journal articleBurne S, Bertucci C, Mazelle C, et al., 2021, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380
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- Citations: 11
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Journal articleKellogg PJ, Bale SD, Goetz K, et al., 2021, , JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 126, ISSN: 2169-9380
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- Citations: 3
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Journal articleLaMoury AT, Hietala H, Plaschke F, et al., 2021, , Journal of Geophysical Research: Space Physics, Vol: 126, Pages: 1-15, ISSN: 2169-9380
Magnetosheath jets are localized high-dynamic pressure pulses originating at Earth's bow shock and propagating earthward through the magnetosheath. Jets can influence magnetospheric dynamics upon impacting the magnetopause; however, many jets dissipate before reaching it. In this study we present a database of 13,096 jets observed by the Time History of Events and Macroscale Interactions during Substorms spacecraft from 2008 to 2018, spanning a solar cycle. Each jet is associated with upstream solar wind conditions from OMNI. We statistically examine how solar wind conditions control the likelihood of jets forming at the shock, and the conditions favorable for jets to propagate through the magnetosheath and reach the magnetopause. We see that, for each solar wind quantity, these two effects are separate, but when combined, we find that jets are over 17 times more likely to reach and potentially impact the magnetopause when the interplanetary magnetic field (IMF) orientation is at a low cone angle, and approximately 8 times more likely during high speed solar wind. Low IMF magnitude, high Alfvén Mach number, and low density approximately double the number of jets at the magnetopause, while urn:x-wiley:21699380:media:jgra56749:jgra56749-math-0001 and dynamic pressure display no net effect. Due to the strong dependence on wind speed, we infer that jet impact rates may be solar cycle dependent as well as vary during solar wind transients. This is an important step towards forecasting the magnetospheric effects of magnetosheath jets, as it allows for predictions of jet impact rates based on measurements of the upstream solar wind.
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Journal articleMallet A, Squire J, Chandran BDG, et al., 2021, , ASTROPHYSICAL JOURNAL, Vol: 918, ISSN: 0004-637X
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- Citations: 43
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Journal articleMozer FS, Bale SD, Bonnell JW, et al., 2021, , ASTROPHYSICAL JOURNAL, Vol: 919, ISSN: 0004-637X
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- Citations: 24
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Journal articleShuster JR, Gershman DJ, Dorelli JC, et al., 2021, , NATURE PHYSICS, Vol: 17, Pages: 1056-+, ISSN: 1745-2473
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- Citations: 21
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Journal articleDesai RT, Freeman M, Eastwood J, et al., 2021, , Geophysical Research Letters, Vol: 48, Pages: 1-11, ISSN: 0094-8276
The magnetopause marks the outer edge of the Earth’s magnetosphere and a distinct boundary between solar wind and magnetospheric plasma populations. In this letter, we use global magneto-hydrodynamic simulations to examine the response of the terrestrial magnetopause to fast-forward interplanetary shocks of various strengths and compare to theoretical predictions. The theory and simulations indicate the magnetopause response can be characterised by three distinct phases; an initial acceleration as inertial forces are overcome, a rapid compressive phase comprising the majority of the distance travelled, and large-scale damped oscillations with amplitudes of the order of an Earth radius. The two approaches agree in predicting subsolar magnetopause oscillations with frequencies2–13 mHz but the simulations notably predict larger amplitudes and weaker damping rates. This phenomenon is of high relevance to space weather forecasting and provides a possible explanation for magnetopause oscillations observed following the large interplanetary shocks of August 1972 and March 1991.
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Journal articleShebanits O, Wahlund J-E, Waite JH, et al., 2021,
<jats:p>Titan’s ionosphere hosts a globally distributed non-trivial dustyion-ion plasma, providing an environment for studies of dustyionospheres that is in many aspects unique in our solar system. Thanksto the Cassini mission, Titan’s ionosphere also features one of thelargest dusty plasma datasets from 126 flybys of the moon over 13 years,from 2004 to 2017. Recent studies have shown that negatively chargeddust dramatically alters the electric properties of plasmas, inparticular planetary ionospheres. Utilizing the full plasma content ofthe moon’s ionosphere (electrons, positive ions and negative ions/dustgrains), we derive the electric conductivities and define the conductivedynamo region. Our results show that using the full plasma contentincreases the Pedersen conductivities at ~1300 kmaltitude by 20% compared to the earlier estimates without charged dust,while the Hall conductivities indicate a reverse Hall effect at~900 km altitude (closest approach) and below. Thedayside conductivities are shown to be factor ~7-9larger than on the nightside, owing to higher dayside plasma densities.</jats:p>
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Journal articleTsui EYL, Toumi R, 2021, , Scientific Reports, Vol: 11, Pages: 1-8, ISSN: 2045-2322
A teleconnection between North Atlantic tropical storms and Amazon fires is investigated as a possible case of compound remote extreme events. The seasonal cycles of the storms and fires are in phase with a maximum around September and have significant inter-annual correlation. Years of high Amazon fire activity are associated with atmospheric conditions over the Atlantic which favour tropical cyclones. We propose that anomalous precipitation and latent heating in the Caribbean, partly caused by tropical storms, leads to a thermal circulation response which creates anomalous subsidence and enhances surface solar heating over the Amazon. The Caribbean storms and precipitation anomalies could thus promote favourable atmospheric conditions for Amazon fire.
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Journal articleLaker R, Horbury TS, Bale SD, et al., 2021, , Astronomy and Astrophysics: a European journal, Vol: 652, Pages: 1-10, ISSN: 0004-6361
Context. The recent launches of Parker Solar Probe, Solar Orbiter (SO), and BepiColombo, along with several older spacecraft, have provided the opportunity to study the solar wind at multiple latitudes and distances from the Sun simultaneously.Aims. We take advantage of this unique spacecraft constellation, along with low solar activity across two solar rotations between May and July 2020, to investigate how the solar wind structure, including the heliospheric current sheet (HCS), varies with latitude.Methods. We visualise the sector structure of the inner heliosphere by ballistically mapping the polarity and solar wind speed from several spacecraft onto the Sun’s source surface. We then assess the HCS morphology and orientation with the in situ data and compare this with a predicted HCS shape.Results. We resolve ripples in the HCS on scales of a few degrees in longitude and latitude, finding that the local orientations of sector boundaries were broadly consistent with the shape of the HCS but were steepened with respect to a modelled HCS at the Sun. We investigate how several CIRs varied with latitude, finding evidence for the compression region affecting slow solar wind outside the latitude extent of the faster stream. We also identified several transient structures associated with HCS crossings and speculate that one such transient may have disrupted the local HCS orientation up to five days after its passage.Conclusions. We have shown that the solar wind structure varies significantly with latitude, with this constellation providing context for solar wind measurements that would not be possible with a single spacecraft. These measurements provide an accurate representation of the solar wind within ±10° latitude, which could be used as a more rigorous constraint on solar wind models and space weather predictions. In the future, this range of latitudes will increase as SO’s orbit becomes more inclined.
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