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252. 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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253. 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

255. 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

257. A young age of formation of Rheasilvia basin on Vesta from floor deformation patterns and crater counts.

Author

Schenk, Paul M., Neesemann, Alicia, Marchi, Simone, Otto, Katharina, Hoogenboom, Trudi, O'Brien, David P., Castillo‐Rogez, Julie, Raymond, Carol A., Russell, Christopher T., and Osinski, Gordon

Subjects
LUNAR craters, FLOORING, DEFORMATIONS (Mechanics), CRATERING, METEORITES
Abstract

Delivery of significant volumes of howardite–eucrite–diogenite (HED) meteorites from Vesta to Earth is linked to the largest impact events on that protoplanet, especially the giant Rheasilvia basin. Dawn mapping of Rheasilvia reveals a well‐preserved impact structure with extensive deformation patterns and moderate superposed cratering. Spiral and radial deformation features across the floor of Rheasilvia are also common to complex craters on Ceres and icy satellites, as well as larger bodies like the Moon, Mars, and Mercury, when floor units are not buried by impact melt and debris. These deformation features predate the solidification of such melt/debris mixtures and are important structural elements in complex craters related to failure in converging floor material during late stages of crater formation. The similarity and commonality of such features and lack of preserved ancient units within Rheasilvia indicate that these patterns formed during the latter stages of the impact event and that the original basin floor and subsequent cratering record are preserved. Updated counts and interpretation of this observed superposed cratering indicate an ~0.8–0.9 Ga age of basin formation, supporting a young impact and ejection age. This young age is consistent with recent Ar‐Ar ages of feldspar grains in HED (Lindsay et al., 2015), and it may also be consistent with ancient bulk Ar‐Ar ages (>~3.2 Ga) for some HEDs because resetting such ages requires prolonged heating from the residual impact heating of rocks left on Vesta during earlier impacts. The complex morphology and recent formation of Rheasilvia basin are also consistent with dynamical estimates for delivery of these meteorites to the Earth–Moon system. [ABSTRACT FROM AUTHOR]

Published
2022
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259. 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

260. 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

261. 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

262. 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

263. 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
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264. 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

265. 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

266. 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

267. 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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268. 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

270. Reconnection site and ion scale turbulence generation

Author

Vaivads, Andris, primary, Liu, Chengming, additional, Khotyaintsev, Yuri V., additional, Graham, Daniel B., additional, Lindqvist, Per-Arne, additional, Torbert, Roy B., additional, Burch, Jim L., additional, Russell, Christopher T., additional, Contel, Olivier Le, additional, Giles, Barbara L., additional, and Gershman, Daniel J., additional

Published
2020
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272. Crustal and time-varying magnetic fields at the InSight landing site on Mars

Author

Johnson, Catherine L., primary, Mittelholz, Anna, additional, Langlais, Benoit, additional, Russell, Christopher T., additional, Ansan, Véronique, additional, Banfield, Don, additional, Chi, Peter J., additional, Fillingim, Matthew O., additional, Forget, Francois, additional, Haviland, Heidi Fuqua, additional, Golombek, Matthew, additional, Joy, Steve, additional, Lognonné, Philippe, additional, Liu, Xinping, additional, Michaut, Chloé, additional, Pan, Lu, additional, Quantin-Nataf, Cathy, additional, Spiga, Aymeric, additional, Stanley, Sabine, additional, Thorne, Shea N., additional, Wieczorek, Mark A., additional, Yu, Yanan, additional, Smrekar, Suzanne E., additional, and Banerdt, William B., additional

Published
2020
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273. The atmosphere of Mars as observed by InSight

Author

Banfield, Don, primary, Spiga, Aymeric, additional, Newman, Claire, additional, Forget, François, additional, Lemmon, Mark, additional, Lorenz, Ralph, additional, Murdoch, Naomi, additional, Viudez-Moreiras, Daniel, additional, Pla-Garcia, Jorge, additional, Garcia, Raphaël F., additional, Lognonné, Philippe, additional, Karatekin, Özgür, additional, Perrin, Clément, additional, Martire, Léo, additional, Teanby, Nicholas, additional, Hove, Bart Van, additional, Maki, Justin N., additional, Kenda, Balthasar, additional, Mueller, Nils T., additional, Rodriguez, Sébastien, additional, Kawamura, Taichi, additional, McClean, John B., additional, Stott, Alexander E., additional, Charalambous, Constantinos, additional, Millour, Ehouarn, additional, Johnson, Catherine L., additional, Mittelholz, Anna, additional, Määttänen, Anni, additional, Lewis, Stephen R., additional, Clinton, John, additional, Stähler, Simon C., additional, Ceylan, Savas, additional, Giardini, Domenico, additional, Warren, Tristram, additional, Pike, William T., additional, Daubar, Ingrid, additional, Golombek, Matthew, additional, Rolland, Lucie, additional, Widmer-Schnidrig, Rudolf, additional, Mimoun, David, additional, Beucler, Éric, additional, Jacob, Alice, additional, Lucas, Antoine, additional, Baker, Mariah, additional, Ansan, Véronique, additional, Hurst, Kenneth, additional, Mora-Sotomayor, Luis, additional, Navarro, Sara, additional, Torres, Josefina, additional, Lepinette, Alain, additional, Molina, Antonio, additional, Marin-Jimenez, Mercedes, additional, Gomez-Elvira, Javier, additional, Peinado, Veronica, additional, Rodriguez-Manfredi, Jose-Antonio, additional, Carcich, Brian T., additional, Sackett, Stephen, additional, Russell, Christopher T., additional, Spohn, Tilman, additional, Smrekar, Suzanne E., additional, and Banerdt, W. Bruce, additional

Published
2020
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274. Initial results from the InSight mission on Mars

Author

Banerdt, W. Bruce, primary, Smrekar, Suzanne E., additional, Banfield, Don, additional, Giardini, Domenico, additional, Golombek, Matthew, additional, Johnson, Catherine L., additional, Lognonné, Philippe, additional, Spiga, Aymeric, additional, Spohn, Tilman, additional, Perrin, Clément, additional, Stähler, Simon C., additional, Antonangeli, Daniele, additional, Asmar, Sami, additional, Beghein, Caroline, additional, Bowles, Neil, additional, Bozdag, Ebru, additional, Chi, Peter, additional, Christensen, Ulrich, additional, Clinton, John, additional, Collins, Gareth S., additional, Daubar, Ingrid, additional, Dehant, Véronique, additional, Drilleau, Mélanie, additional, Fillingim, Matthew, additional, Folkner, William, additional, Garcia, Raphaël F., additional, Garvin, Jim, additional, Grant, John, additional, Grott, Matthias, additional, Grygorczuk, Jerzy, additional, Hudson, Troy, additional, Irving, Jessica C. E., additional, Kargl, Günter, additional, Kawamura, Taichi, additional, Kedar, Sharon, additional, King, Scott, additional, Knapmeyer-Endrun, Brigitte, additional, Knapmeyer, Martin, additional, Lemmon, Mark, additional, Lorenz, Ralph, additional, Maki, Justin N., additional, Margerin, Ludovic, additional, McLennan, Scott M., additional, Michaut, Chloe, additional, Mimoun, David, additional, Mittelholz, Anna, additional, Mocquet, Antoine, additional, Morgan, Paul, additional, Mueller, Nils T., additional, Murdoch, Naomi, additional, Nagihara, Seiichi, additional, Newman, Claire, additional, Nimmo, Francis, additional, Panning, Mark, additional, Pike, W. Thomas, additional, Plesa, Ana-Catalina, additional, Rodriguez, Sébastien, additional, Rodriguez-Manfredi, Jose Antonio, additional, Russell, Christopher T., additional, Schmerr, Nicholas, additional, Siegler, Matt, additional, Stanley, Sabine, additional, Stutzmann, Eléanore, additional, Teanby, Nicholas, additional, Tromp, Jeroen, additional, van Driel, Martin, additional, Warner, Nicholas, additional, Weber, Renee, additional, and Wieczorek, Mark, additional

Published
2020
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275. Ceres: Astrobiological Target and Possible Ocean World

Author

Castillo-Rogez, Julie C., primary, Neveu, Marc, additional, Scully, Jennifer E.C., additional, House, Christopher H., additional, Quick, Lynnae C., additional, Bouquet, Alexis, additional, Miller, Kelly, additional, Bland, Michael, additional, De Sanctis, Maria Cristina, additional, Ermakov, Anton, additional, Hendrix, Amanda R., additional, Prettyman, Thomas H., additional, Raymond, Carol A., additional, Russell, Christopher T., additional, Sherwood, Brent E., additional, and Young, Edward, additional

Published
2020
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276. 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
2020
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279. 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

283. 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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284. 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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286. 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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287. 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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290. 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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292. 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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296. 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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297. Observations of Electromagnetic Electron Holes and Evidence of Cherenkov Whistler Emission

Author

Steinvall, Konrad, Khotyaintsev, Yuri V., Graham, Daniel B., Vaivads, Andris, Le Contel, Olivier, Russell, Christopher T., Steinvall, Konrad, Khotyaintsev, Yuri V., Graham, Daniel B., Vaivads, Andris, Le Contel, Olivier, and Russell, Christopher T.

Abstract

We report observations of electromagnetic electron holes (EHs). We use multispacecraft analysis to quantify the magnetic field contributions of three mechanisms: the Lorentz transform, electron drift within the EH, and Cherenkov emission of whistler waves. The first two mechanisms account for the observed magnetic fields for slower EHs, while for EHs with speeds approaching half the electron Alfven speed, whistler waves excited via the Cherenkov mechanism dominate the perpendicular magnetic field. The excited whistler waves are kinetically damped and typically confined within the EHs.

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

Author

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

Abstract

The description of the local turbulent energy transfer and the high-resolution ion distributions measured by the Magnetospheric Multiscale mission together provide a formidable tool to explore the cross-scale connection between the fluid-scale energy cascade and plasma processes at subion scales. When the small-scale energy transfer is dominated by Alfvenic, correlated velocity, and magnetic field fluctuations, beams of accelerated particles are more likely observed. Here, for the first time, we report observations suggesting the nonlinear wave-particle interaction as one possible mechanism for the energy dissipation in space plasmas.

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

Author

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

Abstract

Naturally occurring chorus emissions are a class of electromagnetic waves found in the space environments of the Earth and other magnetized planets. They play an essential role in accelerating high-energy electrons forming the hazardous radiation belt environment. Chorus typically occurs in two distinct frequency bands separated by a gap. The origin of this two-band structure remains a 50-year old question. Here we report, using NASA's Van Allen Probe measurements, that banded chorus waves are commonly accompanied by two separate anisotropic electron components. Using numerical simulations, we show that the initially excited single-band chorus waves alter the electron distribution immediately via Landau resonance, and suppress the electron anisotropy at medium energies. This naturally divides the electron anisotropy into a low and a high energy components which excite the upper-band and lower-band chorus waves, respectively. This mechanism may also apply to the generation of chorus waves in other magnetized planetary magnetospheres.

Published
2019

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