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251. The boulder population of Vesta

Author

Schröder, Stefan, Carsenty, Uri, Schulzeck, Franziska, Hauber, Ernst, Jaumann, Ralf, Raymond, Carol A., and Russell, Christopher T.

Subjects
boulders, Planetengeologie, Vesta
Published
2019

256. Spacecraft Exploration of Asteroids

Author

Farquhar, Robert, primary, Kawaguchi, Jun’ichiro, additional, Russell, Christopher T., additional, Schwehm, Gerhard, additional, Veverka, Joseph, additional, and Yeomans, Donald, additional

Published
2002
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257. Detection and behavior of Pan wakes in Saturn's A ring

Author

Horn, Linda J., Showalter, Mark R., and Russell, Christopher T.

Subjects
Saturn (Planet) -- Ring system, Planetary rings -- Analysis, Wakes (Aerodynamics) -- Research, Satellites -- Saturn, Astronomy, Earth sciences
Abstract

Six previously unseen Pan wakes are found interior and exterior to the Encke gap in Saturn's A ring, one in the Voyager 2 photopolarimeter (PPS) stellar occultation data and five in the Voyager 1 radio science (RSS) earth occultation data. Pan orbits at the center of the Encke gap and maintains it. Originally it was hypothesized that a wake would be completely damped by the time it reached a longitude of 360 [degrees] relative to Pan. However, five of the six newly detected wakes are at longitudes in excess of 360 [degrees] and are a result of earlier encounters with Pan. The sixth is the first detection of the RSS outer Pan wake. The new PPS inner wake is at a longitude of 389.8 [degrees]. The new RSS inner wakes are at longitudes of 519.4 [degrees] [+ or -] 1.6 [degrees] and 879.4 [degrees] [+ or -] 1.6 [degrees]. The RSS outer wakes are at longitudes of 200.6 [degrees] [+ or -] 1.6 [degrees], 560.6 [degrees] [+ or -] 1.6 [degrees], and 920.6 [degrees] [+ or -] 1.6 [degrees]. Because of the time needed for a wake to develop after encountering Pan, the higher order wakes (longitude > 360 [degrees]) can be more prominent than their lower order counterparts which are superimposed at the same location. The radial dispersion behavior of the Pan wakes are characterized using a Burg autoregressive power spectral algorithm. The wake radial wavelength behavior is compared to a simple model which ignores collisions and self-gravity. The four wakes with longitudes below 360 [degrees] show an average deviation of 0-3% from the predicted wavelengths, indicative of the strength of collective effects. The detection of Pan wakes at longitudes greater than 360 [degrees] demonstrates that wakes persist for much longer than originally hypothesized and may interact with one another. The presence and characteristics of these wakes will provide an important test of kinetic theory models.

Published
1996

259. Use of natural constraints on vector data obtained from a single spinning aircraft

Author

Kepko, Emil L., Khurana, Krishan K., Kivelson, Margaret G., Elphic, Richard C., and Russell, Christopher T.

Subjects
Cluster (Artificial satellite) -- Observations, Magnetosphere -- Observations, Magnetic fields (Cosmic physics) -- Measurement, Electromagnetic measurements -- Methods, Business, Electronics, Electronics and electrical industries
Abstract

Cluster introduces a new generation of spacecraft that will measure the spatial gradients of the magnetic field in the Earth's magnetosphere. As gradients require knowledge of differences, small errors resulting from an inadequate knowledge of the orientations, zero levels and the scale factors of the magnetometer sensors affect the calculation of field gradients disproportionately and must be removed with high accuracy. We show that twelve calibration parameters are required for each of the spacecraft (for a total of 48 for the four spacecraft) to correctly infer the measured magnetic fields at each of the spacecraft. By application of a Fourier transform technique, some of the parameters can be recovered. We will show that errors in eight of the twelve calibration parameters generate coherent monochromatic signals at the first and the second harmonics of the spin frequency in the despun data. These narrow-band signals can be readily characterized because of the natural constraint that low frequency geophysical signals in the Earth's magnetosphere have a broad-band character. We relate the real and the imaginary parts of the monochromatic signals to the eight calibration parameters. We then present a least squares scheme that improves the eight calibration parameters by iteration until the power of the coherent signal superimposed above the broad-band background is minimized. In an accompanying paper, we report on another technique that determines the rest of the calibration parameters by utilizing the natural constraints that [Nabla] [multiplied by] B is zero everywhere and [Nabla] x B is vanishingly small in certain regions of the magnetosphere.

Published
1996

260. Direct evidence of nonstationary collisionless shocks in space plasmas

Author

Dimmock, Andrew P., Russell, Christopher T., Sagdeev, Roald Z., Krasnoselskikh, Vladimir, Walker, Simon N., Carr, Christopher, Dandouras, Iannis, Escoubet, C. Philippe, Ganushkina, Natalia, Gedalin, Michael, Khotyaintsev, Yuri V., Aryan, Homayon, Pulkkinen, Tuija, I, Balikhin, Michael A., Dimmock, Andrew P., Russell, Christopher T., Sagdeev, Roald Z., Krasnoselskikh, Vladimir, Walker, Simon N., Carr, Christopher, Dandouras, Iannis, Escoubet, C. Philippe, Ganushkina, Natalia, Gedalin, Michael, Khotyaintsev, Yuri V., Aryan, Homayon, Pulkkinen, Tuija, I, and Balikhin, Michael A.

Abstract

Collisionless shocks are ubiquitous throughout the universe: around stars, supernova remnants, active galactic nuclei, binary systems, comets, and planets. Key information is carried by electromagnetic emissions from particles accelerated by high Mach number collisionless shocks. These shocks are intrinsically nonstationary, and the characteristic physical scales responsible for particle acceleration remain unknown. Quantifying these scales is crucial, as it affects the fundamental process of redistributing upstream plasma kinetic energy into other degrees of freedom-particularly electron thermalization. Direct in situ measurements of nonstationary shock dynamics have not been reported. Thus, the model that best describes this process has remained unknown. Here, we present direct evidence demonstrating that the transition to nonstationarity is associated with electron-scale field structures inside the shock ramp.

Published
2019
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261. MMS Measurements and Modeling of Peculiar Electromagnetic Ion Cyclotron Waves

Author

Lee, Justin H., Turner, Drew L., ToledoRedondo, Sergio, Vines, Sarah K., Allen, Robert C., Fuselier, Stephen A., Khotyaintsev, Yuri V., Cohen, Ian J., Mauk, Barry H., Russell, Christopher T., Pollock, Craig J., Ergun, Robert E., Lindqvist, PerArne L., Burch, James L., Lee, Justin H., Turner, Drew L., ToledoRedondo, Sergio, Vines, Sarah K., Allen, Robert C., Fuselier, Stephen A., Khotyaintsev, Yuri V., Cohen, Ian J., Mauk, Barry H., Russell, Christopher T., Pollock, Craig J., Ergun, Robert E., Lindqvist, PerArne L., and Burch, James L.

Abstract

Orbiting Earth's dayside outer magnetosphere on 29 September 2015, the Magnetospheric Multiscale (MMS) satellites measured plasma composition, simultaneous electromagnetic ion cyclotron waves, and intermittent fast plasma flows consistent with ultralow frequency waves or convection. Such flows can accelerate typically unobservable low-energy plasma into a measurable energy range of spacecraft plasma instrumentation. We exploit the flow occurrence to ensure measurement of cold ion species alongside the hot particles-consisting of ionospheric heavy ions and solar wind He++-during a subinterval of wave emissions with spectral properties previously described as peculiar. Through application of the composition and multisatellite wave vector data to linear theory, we demonstrate the emissions are in fact consistent with theory, growing naturally in the He++ band with sufficient free energy., Plain Language Summary Electromagnetic ion cyclotron waves are a special class of plasma waves observed in space near Earth or in other magnetized plasmas. They emit electromagnetic energy near the local ion cyclotron frequencies, a relationship that has been studied extensively through theory. But investigations in space via satellite observations have been hindered by an observational problem. Spacecraft charge positive in sunlight due to interactions between sunlight and spacecraft surfaces. Because of this, positively charged ion species with very low energy are invisible to spacecraft plasma instruments. These invisible low‐energy ions are critical to measure to fully understand their effects on the wave emissions. Luckily, electric fields induced by sudden ambient magnetic field changes sometimes provide extra acceleration to these low‐energy ions, helping them enter plasma instrument apertures and be observed. We investigate the electromagnetic waves during one such acceleration interval and use comprehensive plasma instrument measurements to show waves thought to be peculiar are instead behaving consistent with theory. Exploring other times and regions of space under similar measurement conditions may improve our understanding of how the electromagnetic waves are generated and their evolution in space and time., From WoS: Early access - [The article] [...] have been peer-reviewed and accepted for publication.The article content has been finalized, but it has not been assigned to an issue yet.

Published
2019
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264. Earth's Alfvén Wings Driven by the April 2023 Coronal Mass Ejection

Author

Chen, Li‐Jen, Gershman, Daniel, Burkholder, Brandon, Chen, Yuxi, Sarantos, Menelaos, Jian, Lan, Drake, James, Dong, Chuanfei, Gurram, Harsha, Shuster, Jason, Graham, Daniel B., Le Contel, Olivier, Schwartz, Steven J., Fuselier, Stephen, Madanian, Hadi, Pollock, Craig, Liang, Haoming, Argall, Matthew, Denton, Richard E., Rice, Rachel, Beedle, Jason, Genestreti, Kevin, Ardakani, Akhtar, Stanier, Adam, Le, Ari, Ng, Jonathan, Bessho, Naoki, Pandya, Megha, Wilder, Frederick, Gabrielse, Christine, Cohen, Ian, Wei, Hanying, Russell, Christopher T., Ergun, Robert, Torbert, Roy, and Burch, James

Abstract

We report a rare regime of Earth's magnetosphere interaction with sub‐Alfvénic solar wind in which the windsock‐like magnetosphere transforms into one with Alfvén wings. In the magnetic cloud of a Coronal Mass Ejection (CME) on 24 April 2023, NASA's Magnetospheric Multiscale mission distinguishes the following features: (a) unshocked and accelerated low‐beta CME plasma coming directly against Earth's dayside magnetosphere; (b) dynamical wing filaments representing new channels of magnetic connection between the magnetosphere and foot points of the Sun's erupted flux rope; (c) cold CME ions observed with energized counter‐streaming electrons, evidence of CME plasma captured due to by reconnection between magnetic‐cloud and Alfvén‐wing field lines. The reported measurements advance our knowledge of CME interaction with planetary magnetospheres, and open new opportunities to understand how sub‐Alfvénic plasma flows impact astrophysical bodies such as Mercury, moons of Jupiter, and exoplanets close to their host stars. Like supersonically fast fighter jets creating sonic shocks in the air, planet Earth typically moves in the magnetized solar wind at super‐Alfvénic speeds and generates a bow shock. Here we report unprecedented observations of Earth's magnetosphere interacting with a sub‐Alfvénic solar wind brought by an erupted magnetic flux rope from the Sun, called a coronal mass ejection (CME). The terrestrial bow shock disappears, leaving the magnetosphere exposed directly to the cold CME plasma and the strong magnetic field from the Sun's corona. Our results show that the magnetosphere transforms from its typical windsock‐like configuration to having wings that magnetically connect our planet to the Sun. The wings are highways for Earth's plasma to be lost to the Sun, and for the plasma from the foot points of the Sun's erupted flux rope to access Earth's ionosphere. Our work indicates highly dynamic generation and interaction of the wing filaments, shedding new light on how sub‐Alfvénic plasma wind may impact astrophysical bodies in our solar and other stellar systems. MMS observed a rare regime of magnetosphere interaction with unshocked low‐beta CME plasmaWing filaments represent dynamical channels of magnetic connection between the magnetosphere and foot points of the Sun's erupted flux ropeCold CME ions observed on closed field lines, likely generated by dual‐wing reconnection MMS observed a rare regime of magnetosphere interaction with unshocked low‐beta CME plasma Wing filaments represent dynamical channels of magnetic connection between the magnetosphere and foot points of the Sun's erupted flux rope Cold CME ions observed on closed field lines, likely generated by dual‐wing reconnection

Published
2024
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265. Dawn : a mission in developement for exploration of main belt asteroids Vesta and Ceres

Author

Rayman, Marc D, Fraschetti, Thomas C, Russell, Christopher T, and Raymond, Carol A

Subjects
Lunar And Planetary Science And Exploration
Abstract

Dawn is in development for a 2006 launch on a mission to explore main belt asteroids in order to yield insights into important questions about the formation and evolution of the solar system. Its objective is to acquire detailed data from orbit around two complementary bodies, Vesta and Ceres, the two most massive asteroids. The project relies on extensive heritage from other deep-space and Earth-orbiting missions, thus permitting the ambitious objectives to be accomplished with an affordable budget.

Published
2004

266. Packaging a Successful NASA Mission to Reach a Large Audience with a Small Budget. Earth's Dynamic Space: Solar-Terrestrial Physics and NASA's Polar Mission

Author

Fox, Nicola J, Goldberg, Richard, Barnes, Robin J, Sigwarth, John B, Beisser, Kerri B, Moore, Thomas E, Hoffman, Robert A, Russell, Christopher T, Scudder, Jack D, and Spann, James F

Subjects
Space Sciences (General)
Abstract

To showcase the on-going and wide-ranging scope of the Polar science discoveries, the Polar science team has created a one-stop shop for a thorough introduction to geospace physics, in the form of a DVD with supporting website. The DVD, Earth's Dynamic Space: Solar-Terrestrial Physics & NASA's Polar Mission, can be viewed as an end-to-end product or split into individual segments and tailored to lesson plans. Capitalizing on the Polar mission and its amazing science return, the Polar team created an exciting multi-use DVD intended for audiences ranging from a traditional classroom and after school clubs, to museums and science centers. The DVD tackles subjects such as the aurora, the magnetosphere and space weather, whilst highlighting the science discoveries of the Polar mission. This platform introduces the learner to key team members as well as the science principles. Dramatic visualizations are used to illustrate the complex principles that describe Earth's dynamic space. In order to produce such a wide-ranging product on a shoe-string budget, the team poured through existing NASA resources to package them into the Polar story. Team members also created visualizations using Polar data to complement the NASA stock footage. Scientists donated their time to create and review scripts to make this a real team effort, working closely with the award winning audio-visual group at JHU/Applied Physics Laboratory. The team was excited to be invited to join NASA's Sun-Earth Day 2005 E/PO program and the DVD will be distributed as part of the supporting educational packages.

Published
2004

267. Thick escaping magnetospheric ion layer in magnetopause reconnection with MMS observations

Author

Giles, Barbara L., Pollock, C., Moore, Thomas E., Dorelli, John C., Gershman, Daniel J., Paterson, William R., Avanov, Levon A., Chandler, M. O., Coffey, V., Sauvaud, Jean-Andre, Lavraud, Benoit, Russell, Christopher T., Strangeway, Robert J., Genestreti, K. J., Burch, James L., Nagai, Tsugunobu, Kitamura, Naritoshi, Hasegawa, Hiroshi, Shinohara, Iku, Yokota, Shoichiro, Saito, Yoshifumi, Nakamura, Rumi, and Oka, Mitsuo

Abstract

著者人数: 23名, Accepted: 2016-05-18, 資料番号: SA1160113000

Published
2016

268. Shift of the magnetopause reconnection line to the winter hemisphere under southward IMF conditions: Geotail and MMS observations

Author

Pollock, Craig J., Giles, Barbara L., Moore, Thomas E., Dorelli, John C., Gershman, Daniel J., Avanov, Levon A., Paterson, William R., Coffey, V. N., Chandler, M. O., Sauvaud, Jean-Andre, Lavraud, Benoit, Torbert, R. B., Russell, Christopher T., Strangeway, Robert J., Burch, James L., Kitamura, Naritoshi, Hasegawa, Hiroshi, Saito, Yoshifumi, Shinohara, Iku, Yokota, Shoichiro, and Nagai, Tsugunobu

Abstract

著者人数: 21名, Accepted: 2016-05-13, 資料番号: SA1160111000

Published
2016

269. Electron currents and heating in the ion diffusion region of asymmetric reconnection

Author

Graham, D. B., Khotyaintsev, Yu. V., Norgren, C., Vaivads, A., Andre, M., Lindqvist, P.-A., Marklund, G. T., Ergun, R. E., Paterson, William R., Gershman, Daniel J., Giles, Barbara L., Pollock, C. J., Dorelli, John C., Avanov, Levon A., Lavraud, Benoit, Magnes, W., Russell, Christopher T., Strangeway, Robert J., Torbert, R. B., Burch, James L., Saito, Yoshifumi, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Magnetic reconnection, Electron, 01 natural sciences, Magnetic field, electron currents, Geophysics, Hall effect, [SDU]Sciences of the Universe [physics], Electric field, magnetic reconnection, 0103 physical sciences, Physics::Space Physics, electron heating, General Earth and Planetary Sciences, Diffusion current, Atomic physics, Electric current, Diffusion (business), 010306 general physics, 0105 earth and related environmental sciences
Abstract

著者人数: 21名, Accepted: 2016-04-14, 資料番号: SA1160109000

Published
2016

270. Magnetic Fluctuations in the Jovian Magnetosphere

Author

Russell, Christopher T

Subjects
Lunar And Planetary Science And Exploration
Abstract

The engine that drives the jovian magnetosphere is the mass added to the Io ion torus, accelerated to corotational velocities by field-aligned currents that couple the Io torus to the jovian ionosphere. The mass of the torus builds up to an amount that the magnetic forces cannot contain and the plasma, first slowly and then more rapidly, drifts outward. Numerous authors have treated this problem based first on the observations of the Pioneer 10 and 11 flybys; then on Voyager 1 and 2, and Ulysses; and finally most recently the Galileo orbiter. The initial observations revealed the now familiar magnetodisk, in which the field above and below the magnetic equator became quite radial in orientation and much less dipolar. The Galileo observations show this transformation to occur on average at 24 R(sub J) and to often be quite abrupt. These observations are consistent with outward transport of magnetized plasma that moves ever faster radially until about 50 R(sub J) on the nightside where the field lines stretch to the breaking point, reconnection occurs, and plasma and field islands are transported down the tail ultimately removing the mass from the magnetosphere that Io had deposited deep in the inner torus. The reconnection process creates empty flux tubes connected to Jupiter that are buoyant and thought to float inward and replace the flux carried out with the torus plasma. As described above, the jovian magnetosphere could very well be in a state of steady laminar circulation, but indeed it is not. The process is very unsteady and the wave levels can be very intense. The existence of these waves in turn can lead to processes that compete with the radial circulation pattern in removing plasma from the system. These waves can scatter particles so that they precipitate into the ionosphere. This process should be important in the Io torus where the atmospheric loss cone is relatively large and becomes less important as the loss cone decreases in size with radial distance. However, the Io torus is relatively quiet compared to the region outside the torus and it is not obvious without studying this scattering carefully whether the loss in the torus or out of the torus is greater and whether it can act rapidly enough to compete with the radial transport of ions to the tail in the life cycle of the mass added at Io. Closer to Io the ion cyclotron waves are most intense and possibly are associated with the losses in the Io flux tube. The waves are also diagnostic of both the Io atmospheric composition and the size and strength of the massloading process.

Published
2002

271. Polar Magnetic Field Data

Author

Russell, Christopher T and Hoffman, Robert

Subjects
Geophysics
Abstract

At this writing we have received all the CDROMs for the grant period. We have completed generating our timing tables past September 20, 2001. The calibration of the instrument has been checked for the entire mission up to the end of December 2000 and the key parameters provided to the project until the end of December 2000. These data are available to other experimenters over the web at http://www-ssc.igpp.ucla.edu/forms/polar/. High resolution spun data, 8 samples per see, have been created up to November, 2000 and have been made available to the community over the world wide web. This is a new data set that was a major effort this year. Our near term plans are to continue to provide key parameter data to the Polar project with the highest possible speed and to continue to reduce all high resolution magnetometer data and provide these data to the scientific community over the web.

Published
2002

273. Statistical Survey of Collisionless Dissipation in the Terrestrial Magnetosheath.

Author

Yanwen Wang, Bandyopadhyay, Riddhi, Chhiber, Rohit, Matthaeus, William H., Chasapis, Alexandros, Yan Yang, Wilder, Frederick D., Gershman, Daniel J., Giles, Barbara L., Pollock, Craig J., Dorelli, John, Russell, Christopher T., Strangeway, Robert J., Torbert, Roy T., Moore, Thomas E., and Burch, James L.

Subjects
ELECTROMAGNETIC waves, PLASMA heating, COLLISIONLESS plasmas, INTERNAL energy (Thermodynamics), SURVEYS
Abstract

Kinetic dissipation of turbulence is an important physical process occurring in collisionless plasmas. Using in-situ data from the Magnetospheric Multiscale (MMS) Mission, we investigate the statistical distribution of kinetic dissipation in the terrestrial magnetosheath. We make use of an analysis of the Vlasov-Maxwell equations that provides a general description of transfer of internal energy, fluid-flow energy, and electromagnetic energy in collisionless plasma, including both spatial transport and conversion between forms. In particular, we focus on the channels that separately produce proton and electron internal energies. Applying those results to MMS burst-mode data obtained in the weakly collisional, turbulent magnetosheath plasma, it is possible to quantify contributions to dissipation from the compressive pressure-dilatation channel, and from the incompressive pressure-strain channel, for both plasma species. We also employ a simple spatial filtering approach as a first step to quantifying plasma heating at large and small scales. The analysis is carried out for 50 selected turbulent data intervals, and statistical distributions of the results are presented. [ABSTRACT FROM AUTHOR]

Published
2021
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274. Magnetized or Unmagnetized: Ambiguity Persists Following Galileo's Encounters with Io in 1999 and 2000

Author

Kivelson, Margaret G, Khurana, Krishan K, Russell, Christopher T, Joy, Steven P, Volwerk, Martin, Walker, Raymond J, Zimmer, Christophe, and Linker, Jon A

Subjects
Lunar And Planetary Science And Exploration
Abstract

Magnetometer data from Galileo's close encounters with Io do not establish absolutely either the existence or absence of an internal magnetic moment because the measurements were made in regions where plasma currents contribute sizable magnetic perturbations. Data from an additional encounter where the closest approaches were made beneath Io's south polar regions, were lost. The recent passes enhance our understanding of the interaction of Io and its flux tube with the torus, and narrows the limits on possible internal sources of magnetic fields. Simple field-draping arguments account for some aspects of the observed rotations. Analyses in terms of both a magnetized and an unmagnetized Io are considered. Data from the February 2000 pass disqualify a strongly magnetized Io (surface equatorial field stronger than the background field) but do not disqualify a weakly magnetized Io (surface equatorial field of the order of Ganymede's but smaller than the background field at Io). Models imply that if Io is magnetized, its magnetic moment is not absolutely antialigned with the rotation axis. The inferred tilt is consistent with contributions from an inductive field on the order of those observed at Europa and Callisto. The currents would flow in the outer mantle or aesthenosphere if an induced field is present. Wave perturbations differing on flux tubes that do or do not link directly to Io and its ionosphere suggest the following: (1) the latter flux tubes are almost stagnant in Io's frame; and (2) a unipolar inductor correctly models the currents linking Io to Jupiter's ionosphere.

Published
2001
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275. Investigation of High-Latitude Phenomena Using Polar Data and Global Simulations

Author

Russell, Christopher T and Hoffman, Robert

Subjects
Geophysics
Abstract

The goal of this one-year project was to use data from the Polar satellite in conjunction with global simulations of Earth's magnetosphere to investigate phenomena in the high-latitude magnetosphere. Specifically, we addressed reconnection at the cusp during periods of northward interplanetary magnetic field (IMF), and the effects of substorms on the high-latitude magnetosphere.

Published
2001

276. Saturn’s magnetic field revealed by the Cassini Grand Finale

Author

Dougherty, Michele K., Cao, Hao, Khurana, Krishan K., Hunt, Gregory J., Provan, Gabrielle, Kellock, Stephen, Burton, Marcia E., Burk, Thomas A., Bunce, Emma J., Cowley, Stanley W. H., Kivelson, Margaret G., Russell, Christopher T., and Southwood, David J.

Subjects
Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics
Abstract

INTRODUCTION: Starting on 26 April 2017, the Grand Finale phase of the Cassini mission took the spacecraft through the gap between Saturn’s atmosphere and the inner edge of its innermost ring (the D-ring) 22 times, ending with a final plunge into the atmosphere on 15 September 2017. This phase offered an opportunity to investigate Saturn’s internal magnetic field and the electromagnetic environment between the planet and its rings. The internal magnetic field is a diagnostic of interior structure, dynamics, and evolution of the host planet. Rotating convective motion in the highly electrically conducting layer of the planet is thought to maintain the magnetic field through the magnetohydrodynamic (MHD) dynamo process. Saturn’s internal magnetic field is puzzling because of its high symmetry relative to the spin axis, known since the Pioneer 11 flyby. This symmetry prevents an accurate determination of the rotation rate of Saturn’s deep interior and challenges our understanding of the MHD dynamo process because Cowling’s theorem precludes a perfectly axisymmetric magnetic field being maintained through an active dynamo. RATIONALE: The Cassini fluxgate magnetometer was capable of measuring the magnetic field with a time resolution of 32 vectors per s and up to 44,000 nT, which is about twice the peak field strength encountered during the Grand Finale orbits. The combination of star cameras and gyroscopes onboard Cassini provided the attitude determination required to infer the vector components of the magnetic field. External fields from currents in the magnetosphere were modeled explicitly, orbit by orbit. RESULTS: Saturn’s magnetic equator, where the magnetic field becomes parallel to the spin axis, is shifted northward from the planetary equator by 2808.5 ± 12 km, confirming the north-south asymmetric nature of Saturn’s magnetic field. After removing the systematic variation with distance from the spin axis, the peak-to-peak “longitudinal” variation in Saturn’s magnetic equator position is

Published
2018

277. Energy partitioning constraints at kinetic scales in low-beta turbulence

Author

Gershman, Daniel J., F-Vinas, Adolfo, Dorelli, John C., Goldstein, Melvyn L., Shuster, Jason, Avanov, Levon A., Boardsen, Scott A., Stawarz, Julia E., Schwartz, Steven J., Schiff, Conrad, Lavraud, Benoit, Paterson, William R., Giles, Barbara L., Pollock, Craig J., Strangeway, Robert J., Russell, Christopher T., Torbert, Roy B., Moore, Thomas E., Burch, James L., and Saito, Yoshifumi

Subjects
Physics, 010504 meteorology & atmospheric sciences, Whistler, Turbulence, Magnetosphere, Plasma, Condensed Matter Physics, Kinetic energy, 01 natural sciences, Electromagnetic radiation, Computational physics, Physics::Fluid Dynamics, Magnetosheath, Physics::Space Physics, 0103 physical sciences, Magnetospheric Multiscale Mission, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

著者人数: 20名, Accepted: 2018-01, 資料番号: SA1170261000

Published
2018

278. Multiscale Currents Observed by MMS in the Flow Braking Region

Author

Nakamura, Rumi, Varsani, Ali, Genestreti, Kevin J, Le Contel, Olivier, Nakamura, Takuma, Baumjohann, Wolfgang, Nagai, Tsugunobu, Artemyev, Anton, Birn, Joachim, Sergeev, Victor A, Apatenkov, Sergey, Ergun, Robert E, Fuselier, Stephen A, Gershman, Daniel J, Giles, Barbara J, Khotyaintsev, Yuri V, Lindqvist, Per-Arne, Magnes, Werner, Mauk, Barry, Petrukovich, Anatoli, Russell, Christopher T, Stawarz, Julia, Strangeway, Robert J, Anderson, Brian, Burch, James L, Bromund, Ken R, Cohen, Ian, Fischer, David, Jaynes, Allison, Kepko, Laurence, Le, Guan, Plaschke, Ferdinand, Reeves, Geoff, Singer, Howard J, Slavin, James A, Torbert, Roy B, Turner, Drew L, Laboratoire de Physique des Plasmas (LPP), Université Paris-Saclay-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École polytechnique (X)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Southwest Research Institute [San Antonio] (SwRI), The University of Texas at San Antonio (UTSA), NASA Goddard Space Flight Center (GSFC), Royal Institute of Technology [Stockholm] (KTH ), Institute of Geophysics and Planetary Physics [Los Angeles] (IGPP), University of California [Los Angeles] (UCLA), and University of California-University of California

Subjects
Fusion, plasma och rymdfysik, plasma sheet boundary, Physics::Plasma Physics, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], magnetic reconnection, Physics::Space Physics, flow braking, field‐aligned current, Magnetospheric Multiscale, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Fusion, Plasma and Space Physics, Astronomical and Space Sciences, Atmospheric Sciences
Abstract

International audience; We present characteristics of current layers in the off-equatorial near-Earth plasma sheet boundary observed with high time-resolution measurements from the Magnetospheric Multiscale mission during an intense substorm associated with multiple dipolarizations. The four Magnetospheric Multiscale spacecraft, separated by distances of about 50 km, were located in the southern hemisphere in the dusk portion of a substorm current wedge. They observed fast flow disturbances (up to about 500 km/s), most intense in the dawn-dusk direction. Field-aligned currents were observed initially within the expanding plasma sheet, where the flow and field disturbances showed the distinct pattern expected in the braking region of localized flows. Subsequently, intense thin field-aligned current layers were detected at the inner boundary of equatorward moving flux tubes together with Earthward streaming hot ions. Intense Hall current layers were found adjacent to the field-aligned currents. In particular, we found a Hall current structure in the vicinity of the Earthward streaming ion jet that consisted of mixed ion components, that is, hot unmagnetized ions, cold E × B drifting ions, and magnetized electrons. Our observations show that both the near-Earth plasma jet diversion and the thin Hall current layers formed around the reconnection jet boundary are the sites where diversion of the perpendicular currents take place that contribute to the observed field-aligned current pattern as predicted by simulations of reconnection jets. Hence, multiscale structure of flow braking is preserved in the field-aligned currents in the off-equatorial plasma sheet and is also translated to ionosphere to become a part of the substorm field-aligned current system.

Published
2018

279. How accurately can we measure the reconnection rate $E_M$ for the MMS diffusion region event of 2017-07-11?

Author

Genestreti, Kevin J., Nakamura, Takuma, Nakamura, Rumi, Denton, Richard E., Torbert, Roy B., Burch, James L., Plaschke, Ferdinand, Fuselier, Stephen A., Ergun, Robert E., Giles, Barbara L., and Russell, Christopher T.

Subjects
Physics - Space Physics, Physics::Space Physics, FOS: Physical sciences, Space Physics (physics.space-ph)
Abstract

We investigate the accuracy with which the reconnection electric field $E_M$ can be determined from in-situ plasma data. We study the magnetotail electron diffusion region observed by NASA's Magnetospheric Multiscale (MMS) on 2017-07-11 at 22:34 UT and focus on the very large errors in $E_M$ that result from errors in an $LMN$ boundary-normal coordinate system. We determine several $LMN$ coordinates for this MMS event using several different methods. We use these $M$ axes to estimate $E_M$. We find some consensus that the reconnection rate was roughly $E_M$=3.2 mV/m $\pm$ 0.06 mV/m, which corresponds to a normalized reconnection rate of $0.18\pm0.035$. Minimum variance analysis of the electron velocity (MVA-$v_e$), MVA of $E$, minimization of Faraday residue, and an adjusted version of the maximum directional derivative of the magnetic field (MDD-$B$) technique all produce {reasonably} similar coordinate axes. We use virtual MMS data from a particle-in-cell simulation of this event to estimate the errors in the coordinate axes and reconnection rate associated with MVA-$v_e$ and MDD-$B$. The $L$ and $M$ directions are most reliably determined by MVA-$v_e$ when the spacecraft observes a clear electron jet reversal. When the magnetic field data has errors as small as 0.5\% of the background field strength, the $M$ direction obtained by MDD-$B$ technique may be off by as much as 35$^\circ$. The normal direction is most accurately obtained by MDD-$B$. Overall, we find that these techniques were able to identify $E_M$ from the virtual data within error bars $\geq$20\%., Comment: Submitted to JGR - Space Physics

Published
2018
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280. Loss of the Martian atmosphere to space: Present-day loss rates determined from MAVEN observations and integrated loss through time

Author

Jakosky , Bruce, Brain , David, Chaffin , Michael, Curry , Shannon M., Deighan , Justin, Grebowsky , Joseph, Halekas , Jasper, Leblanc , François, Lillis , Robert, Luhmann , Janet, Andersson , Laila, André , Nicolas, Andrews , David, Baird , Darren, Baker , Daniel, Bell , Jared, Benna , Mehdi, Bhattacharyya , Dolon, Bougher , Stephen, Bowers , Charlie, Chamberlin , Phillip, Chaufray , Jean-Yves, Clarke , John, Collinson , Glyn, Combi , Michael, Connerney , Jack, Connour , Kyle, Correira , J., Crabb , Kyle, Crary , Frank, Cravens , Thomas, Crismani , Matteo, Delory , Greg, Dewey , Ryan, DiBraccio , Gina, Dong , Chuanfei, Dong , Yaxue, Dunn , Patrick, Egan , Hilary, Elrod , Meredith K., England , Scott, Eparvier , Frank, Ergun , Robert, Eriksson , Anders, Esman , Teresa, Espley , Jared, Evans , S., Fallows , Kathryn, Fang , Xiaohua, Fillingim , Matthew, Flynn , C., Fogle , A., Fowler , Christopher M., Fox , Jane L., Fujimoto , Masaki, Garnier , Philippe, Girazian , Zachary, Groeller , Hannes, Gruesbeck , Jacob, Hamil , O., Hanley , K., Hara , Takuya, Harada , Yuki, Hermann , Jacob, Holmberg , Mika, Holsclaw , Greg, Houston , S., Inui , S., Jain , Sonal, Jolitz , Rebecca, Kotova , Anna, Kuroda , Takeshi, Larson , Davin, Lee , Yuni, Lee , C., Lefèvre , Franck, Lentz , Christy, Lo , D., Lugo , Rafael, Ma , Yingjuan, Mahaffy , Paul R., Marquette , Melissa, Matsumoto , Y., Mayyasi , Majd, Mazelle , Christian, Mcclintock , William, McFadden , Jim, Medvedev , A., Mendillo , Michael, Meziane , K., Milby , Zachariah, Mitchell , D., Modolo , Ronan, Montmessin , Franck, Nagy , Andrew, Nakagawa , H., Narvaez , Clara, Olsen , Kirk, Pawlowski , D., Peterson , William, Rahmati , Ali, Roeten , Kali, Romanelli , Norberto, Ruhunusiri , Suranga, Russell , Christopher T., Sakai , Shotaro, Schneider , Nicholas, Seki , K., Sharrar , R., Shaver , S., Siskind , David E., Slipski , Marek, Soobiah , Yasir, Steckiewicz , Morgane, Stevens , Michael, Stewart , Ian, Laboratory for Atmospheric and Space Physics [Boulder] ( LASP ), University of Colorado Boulder [Boulder], Space Sciences Laboratory [Berkeley] ( SSL ), University of California [Berkeley], NASA Goddard Space Flight Center ( GSFC ), Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa], HEPPI - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales ( LATMOS ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de recherche en astrophysique et planétologie ( IRAP ), Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), Swedish Institute of Space Physics [Uppsala] ( IRF ), NASA Johnson Space Center ( JSC ), NASA, National Institute of Aerospace [Hampton] ( NIA ), Center for Space Physics [Boston] ( CSP ), Boston University [Boston] ( BU ), Department of Climate and Space Sciences and Engineering ( CLaSP ), University of Michigan [Ann Arbor], Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] ( AOSS ), Communications and Power Industries ( CPI ), Department of Physics and Astronomy [Lawrence], University of Kansas [Lawrence] ( KU ), Princeton University, University of Arizona, Wright State University [Dayton], Institute of Space and Astronautical Science ( ISAS ), University of Kansas, Department of Physics and Astronomy [Ames, Iowa], Iowa State University ( ISU ), The University of Tokyo, National Institute of Information and Communications Technology ( NICT ), IMPEC - LATMOS, Analytical Mechanics Associates, Inc., University of California at Los Angeles [Los Angeles] ( UCLA ), Max-Planck-Institut für Sonnensystemforschung ( MPS ), Tohoku University [Sendai], Eastern Michigan University, Institute of Geophysics and Planetary Physics [Los Angeles] ( IGPP ), Department of Earth and Planetary Science [Tokyo], and Naval Research Laboratory ( NRL )

Subjects
Mars atmosphere, [ PHYS.PHYS.PHYS-AO-PH ] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atmosphere, Magnetospheres, Solar wind, Mars, Mars climate
Abstract

International audience; Observations of the Mars upper atmosphere made from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft have been used to determine the loss rates of gas from the upper atmosphere to space for a complete Mars year (16 Nov 2014 – 3 Oct 2016). Loss rates for H and O are sufficient to remove ∼2-3 kg/s to space. By itself, this loss would be significant over the history of the planet. In addition, loss rates would have been greater early in history due to the enhanced solar EUV and more-active Sun. Integrated loss, based on current processes whose escape rates in the past are adjusted according to expected solar evolution, would have been as much as 0.8 bar CO2 or 23 m global equivalent layer of H2O; these losses are likely to be lower limits due to the nature of the extrapolation of loss rates to the earliest times. Combined with the lack of surface or subsurface reservoirs for CO2 that could hold remnants of an early, thick atmosphere, these results suggest that loss of gas to space has been the dominant process responsible for changing the climate of Mars from an early, warmer environment to the cold, dry one that we see today.

Published
2018

281. Generation of turbulence in Kelvin-Helmholtz vortices at the Earth's magnetopause: Magnetospheric Multiscale observations

Author

Hasegawa, Hiroshi, primary, Nakamura, Takuma, additional, Gershman, Daniel J, additional, Nariyuki, Yasuhiro, additional, Adolfo, Viñas, additional, Giles, Barbara L., additional, Lavraud, Benoit, additional, Russell, Christopher T., additional, Khotyaintsev, Yuri V., additional, Ergun, Robert E, additional, and Yoshifumi, Saito, additional

Published
2019
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282. MMS Measurements and Modeling of Peculiar Electromagnetic Ion Cyclotron Waves

Author

Lee, Justin H., primary, Turner, Drew L., additional, Toledo‐Redondo, Sergio, additional, Vines, Sarah K., additional, Allen, Robert C., additional, Fuselier, Stephen A., additional, Khotyaintsev, Yuri V., additional, Cohen, Ian J., additional, Mauk, Barry H., additional, Russell, Christopher T., additional, Pollock, Craig J., additional, Ergun, Robert E., additional, Lindqvist, Per‐Arne L., additional, and Burch, James L., additional

Published
2019
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284. Origin of two-band chorus in the radiation belt of Earth

Author

Li, Jinxing, primary, Bortnik, Jacob, additional, An, Xin, additional, Li, Wen, additional, Angelopoulos, Vassilis, additional, Thorne, Richard M., additional, Russell, Christopher T., additional, Ni, Binbin, additional, Shen, Xiaochen, additional, Kurth, William S., additional, Hospodarsky, George B., additional, Hartley, David P., additional, Funsten, Herbert O., additional, Spence, Harlan E., additional, and Baker, Daniel N., additional

Published
2019
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285. Dissipation of Earthward Propagating Flux Rope Through Re‐reconnection with Geomagnetic Field: An MMS Case Study

Author

Poh, Gangkai, primary, Slavin, James A., additional, Lu, San, additional, Le, Guan, additional, Ozturk, Dogacan Su, additional, Sun, Wei‐Jie, additional, Zou, Shasha, additional, Eastwood, Jonathan P., additional, Nakamura, Rumi, additional, Baumjohann, Wolfgang, additional, Russell, Christopher T., additional, Gershman, Daniel J., additional, Giles, Barbara L., additional, Pollock, Craig J., additional, Moore, Thomas E., additional, Torbert, Roy B., additional, and Burch, James L., additional

Published
2019
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288. Modeling Wind‐Driven Ionospheric Dynamo Currents at Mars: Expectations for InSight Magnetic Field Measurements

Author

Lillis, Robert J., primary, Fillingim, Matthew O., additional, Ma, Yingjuan, additional, Gonzalez‐Galindo, Francisco, additional, Forget, François, additional, Johnson, Catherine L., additional, Mittelholz, Anna, additional, Russell, Christopher T., additional, Andersson, Laila, additional, and Fowler, Christopher M., additional

Published
2019
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290. Spectrophotometric modeling and mapping of Ceres

Author

Li, Jian-Yang, primary, Schröder, Stefan E., additional, Mottola, Stefano, additional, Nathues, Andreas, additional, Castillo-Rogez, Julie C., additional, Schorghofer, Norbert, additional, Williams, David A., additional, Ciarniello, Mauro, additional, Longobardo, Andrea, additional, Raymond, Carol A., additional, and Russell, Christopher T., additional

Published
2019
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293. Synthesis of the special issue: The formation and evolution of Ceres’ Occator crater

Author

Scully, Jennifer E.C., primary, Bowling, Timothy, additional, Bu, Caixia, additional, Buczkowski, Debra L., additional, Longobardo, Andrea, additional, Nathues, Andreas, additional, Neesemann, Adrian, additional, Palomba, Ernesto, additional, Quick, Lynnae C., additional, Raponi, Andrea, additional, Ruesch, Ottaviano, additional, Schenk, Paul M., additional, Stein, Nathan T., additional, Thomas, E.C., additional, Russell, Christopher T., additional, Castillo-Rogez, Julie C., additional, Raymond, Carol A., additional, and Jaumann, Ralf, additional

Published
2019
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294. Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event

Author

Nakamura, Rumi, primary, Genestreti, Kevin J., additional, Nakamura, Takuma, additional, Baumjohann, Wolfgang, additional, Varsani, Ali, additional, Nagai, Tsugunobu, additional, Bessho, Naoki, additional, Burch, James L., additional, Denton, Richard E., additional, Eastwood, Jonathan P., additional, Ergun, Robert E., additional, Gershman, Daniel J., additional, Giles, Barbara L., additional, Hasegawa, Hiroshi, additional, Hesse, Michael, additional, Lindqvist, Per‐Arne, additional, Russell, Christopher T., additional, Stawarz, Julia E., additional, Strangeway, Robert J., additional, and Torbert, Roy B., additional

Published
2019
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295. Direct evidence of nonstationary collisionless shocks in space plasmas

Author

Dimmock, Andrew P., primary, Russell, Christopher T., additional, Sagdeev, Roald Z., additional, Krasnoselskikh, Vladimir, additional, Walker, Simon N., additional, Carr, Christopher, additional, Dandouras, Iannis, additional, Escoubet, C. Philippe, additional, Ganushkina, Natalia, additional, Gedalin, Michael, additional, Khotyaintsev, Yuri V., additional, Aryan, Homayon, additional, Pulkkinen, Tuija I., additional, and Balikhin, Michael A., additional

Published
2019
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296. Turbulence-Driven Ion Beams in the Magnetospheric Kelvin-Helmholtz Instability

Author

Sorriso-Valvo, Luca, primary, Catapano, Filomena, additional, Retinò, Alessandro, additional, Le Contel, Olivier, additional, Perrone, Denise, additional, Roberts, Owen W., additional, Coburn, Jesse T., additional, Panebianco, Vincenzo, additional, Valentini, Francesco, additional, Perri, Silvia, additional, Greco, Antonella, additional, Malara, Francesco, additional, Carbone, Vincenzo, additional, Veltri, Pierluigi, additional, Pezzi, Oreste, additional, Fraternale, Federico, additional, Di Mare, Francesca, additional, Marino, Raffaele, additional, Giles, Barbara, additional, Moore, Thomas E., additional, Russell, Christopher T., additional, Torbert, Roy B., additional, Burch, Jim L., additional, and Khotyaintsev, Yuri V., additional

Published
2019
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298. The surface composition of Ceres’ Ezinu quadrangle analyzed by the Dawn mission

Author

Combe, Jean-Philippe, primary, Singh, Sandeep, additional, Johnson, Katherine E., additional, McCord, Thomas B., additional, De Sanctis, Maria Cristina, additional, Ammannito, Eleonora, additional, Carrozzo, Filippo Giacomo, additional, Ciarniello, Mauro, additional, Frigeri, Alessandro, additional, Raponi, Andrea, additional, Tosi, Federico, additional, Zambon, Francesca, additional, Scully, Jennifer E.C., additional, Raymond, Carol A., additional, and Russell, Christopher T., additional

Published
2019
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299. Exposed H2O-rich areas detected on Ceres with the dawn visible and infrared mapping spectrometer

Author

Combe, Jean-Philippe, primary, Raponi, Andrea, additional, Tosi, Federico, additional, De Sanctis, Maria Cristina, additional, Carrozzo, Filippo Giacomo, additional, Zambon, Francesca, additional, Ammannito, Eleonora, additional, Hughson, Kynan H.G., additional, Nathues, Andreas, additional, Hoffmann, Martin, additional, Platz, Thomas, additional, Thangjam, Guneshwar, additional, Schorghofer, Norbert, additional, Schröder, Stefan, additional, Byrne, Shane, additional, Landis, Margaret E., additional, Ruesch, Ottaviano, additional, McCord, Thomas B., additional, Johnson, Katherine E., additional, Singh, Sandeep Magar, additional, Raymond, Carol A., additional, and Russell, Christopher T., additional

Published
2019
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