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Rymer AM, Mauk BH, Hill TW, Paranicas C, André N, Sittler EC, Mitchell DG, Smith HT, Johnson RE, Coates AJ, Young DT, Bolton SJ, Thomsen MF, Dougherty MK. Electron sources in Saturn's magnetosphere. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006ja012017] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Tokar RL, Johnson RE, Hill TW, Pontius DH, Kurth WS, Crary FJ, Young DT, Thomsen MF, Reisenfeld DB, Coates AJ, Lewis GR, Sittler EC, Gurnett DA. The Interaction of the Atmosphere of Enceladus with Saturn's Plasma. Science 2006; 311:1409-12. [PMID: 16527967 DOI: 10.1126/science.1121061] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
During the 14 July 2005 encounter of Cassini with Enceladus, the Cassini Plasma Spectrometer measured strong deflections in the corotating ion flow, commencing at least 27 Enceladus radii (27 x 252.1 kilometers) from Enceladus. The Cassini Radio and Plasma Wave Science instrument inferred little plasma density increase near Enceladus. These data are consistent with ion formation via charge exchange and pickup by Saturn's magnetic field. The charge exchange occurs between neutrals in the Enceladus atmosphere and corotating ions in Saturn's inner magnetosphere. Pickup ions are observed near Enceladus, and a total mass loading rate of about 100 kilograms per second (3 x 10(27) H(2)O molecules per second) is inferred.
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Young DT, Berthelier JJ, Blanc M, Burch JL, Bolton S, Coates AJ, Crary FJ, Goldstein R, Grande M, Hill TW, Johnson RE, Baragiola RA, Kelha V, McComas DJ, Mursula K, Sittler EC, Svenes KR, Szegö K, Tanskanen P, Thomsen MF, Bakshi S, Barraclough BL, Bebesi Z, Delapp D, Dunlop MW, Gosling JT, Furman JD, Gilbert LK, Glenn D, Holmlund C, Illiano JM, Lewis GR, Linder DR, Maurice S, McAndrews HJ, Narheim BT, Pallier E, Reisenfeld D, Rymer AM, Smith HT, Tokar RL, Vilppola J, Zinsmeyer C. Composition and Dynamics of Plasma in Saturn's Magnetosphere. Science 2005; 307:1262-6. [PMID: 15731443 DOI: 10.1126/science.1106151] [Citation(s) in RCA: 257] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
During Cassini's initial orbit, we observed a dynamic magnetosphere composed primarily of a complex mixture of water-derived atomic and molecular ions. We have identified four distinct regions characterized by differences in both bulk plasma properties and ion composition. Protons are the dominant species outside about 9 RS (where RS is the radial distance from the center of Saturn), whereas inside, the plasma consists primarily of a corotating comet-like mix of water-derived ions with approximately 3% N+. Over the A and B rings, we found an ionosphere in which O2+ and O+ are dominant, which suggests the possible existence of a layer of O2 gas similar to the atmospheres of Europa and Ganymede.
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29
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Crary FJ, Clarke JT, Dougherty MK, Hanlon PG, Hansen KC, Steinberg JT, Barraclough BL, Coates AJ, Gérard JC, Grodent D, Kurth WS, Mitchell DG, Rymer AM, Young DT. Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae. Nature 2005; 433:720-2. [PMID: 15716946 DOI: 10.1038/nature03333] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2004] [Accepted: 12/27/2004] [Indexed: 11/09/2022]
Abstract
The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms, but the relation between the solar wind and the dynamics of the outer planets' magnetospheres is poorly understood. Jupiter's magnetospheric dynamics and aurorae are dominated by processes internal to the jovian system, whereas Saturn's magnetosphere has generally been considered to have both internal and solar-wind-driven processes. This hypothesis, however, is tentative because of limited simultaneous solar wind and magnetospheric measurements. Here we report solar wind measurements, immediately upstream of Saturn, over a one-month period. When combined with simultaneous ultraviolet imaging we find that, unlike Jupiter, Saturn's aurorae respond strongly to solar wind conditions. But in contrast to Earth, the main controlling factor appears to be solar wind dynamic pressure and electric field, with the orientation of the interplanetary magnetic field playing a much more limited role. Saturn's magnetosphere is, therefore, strongly driven by the solar wind, but the solar wind conditions that drive it differ from those that drive the Earth's magnetosphere.
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30
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McComas DJ, Schwadron NA, Crary FJ, Elliott HA, Young DT, Gosling JT, Thomsen MF, Sittler E, Berthelier JJ, Szego K, Coates AJ. The interstellar hydrogen shadow: Observations of interstellar pickup ions beyond Jupiter. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2003ja010217] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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31
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Gurnett DA, Kurth WS, Hospodarsky GB, Persoon AM, Zarka P, Lecacheux A, Bolton SJ, Desch MD, Farrell WM, Kaiser ML, Ladreiter HP, Rucker HO, Galopeau P, Louarn P, Young DT, Pryor WR, Dougherty MK. Control of Jupiter's radio emission and aurorae by the solar wind. Nature 2002; 415:985-7. [PMID: 11875556 DOI: 10.1038/415985a] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Radio emissions from Jupiter provided the first evidence that this giant planet has a strong magnetic field and a large magnetosphere. Jupiter also has polar aurorae, which are similar in many respects to Earth's aurorae. The radio emissions are believed to be generated along the high-latitude magnetic field lines by the same electrons that produce the aurorae, and both the radio emission in the hectometric frequency range and the aurorae vary considerably. The origin of the variability, however, has been poorly understood. Here we report simultaneous observations using the Cassini and Galileo spacecraft of hectometric radio emissions and extreme ultraviolet auroral emissions from Jupiter. Our results show that both of these emissions are triggered by interplanetary shocks propagating outward from the Sun. When such a shock arrives at Jupiter, it seems to cause a major compression and reconfiguration of the magnetosphere, which produces strong electric fields and therefore electron acceleration along the auroral field lines, similar to the processes that occur during geomagnetic storms at the Earth.
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32
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Gladstone GR, Waite JH, Grodent D, Lewis WS, Crary FJ, Elsner RF, Weisskopf MC, Majeed T, Jahn JM, Bhardwaj A, Clarke JT, Young DT, Dougherty MK, Espinosa SA, Cravens TE. A pulsating auroral X-ray hot spot on Jupiter. Nature 2002; 415:1000-3. [PMID: 11875561 DOI: 10.1038/4151000a] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Jupiter's X-ray aurora has been thought to be excited by energetic sulphur and oxygen ions precipitating from the inner magnetosphere into the planet's polar regions. Here we report high-spatial-resolution observations that demonstrate that most of Jupiter's northern auroral X-rays come from a 'hot spot' located significantly poleward of the latitudes connected to the inner magnetosphere. The hot spot seems to be fixed in magnetic latitude and longitude and occurs in a region where anomalous infrared and ultraviolet emissions have also been observed. We infer from the data that the particles that excite the aurora originate in the outer magnetosphere. The hot spot X-rays pulsate with an approximately 45-min period, a period similar to that reported for high-latitude radio and energetic electron bursts observed by near-Jupiter spacecraft. These results invalidate the idea that jovian auroral X-ray emissions are mainly excited by steady precipitation of energetic heavy ions from the inner magnetosphere. Instead, the X-rays seem to result from currently unexplained processes in the outer magnetosphere that produce highly localized and highly variable emissions over an extremely wide range of wavelengths.
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Rymer AM, Coates AJ, Svenes K, Abel GA, Linder DR, Narheim B, Thomsen M, Young DT. Cassini Plasma Spectrometer Electron Spectrometer measurements during the Earth swing-by on August 18, 1999. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2001ja900087] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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34
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Abel GA, Coates AJ, Rymer AM, Linder DR, Thomsen MF, Young DT, Dougherty MK. Cassini Plasma Spectrometer observations of bidirectional lobe electrons during the Earth flyby, August 18, 1999. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2001ja900076] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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35
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Waite JH, Gladstone GR, Lewis WS, Goldstein R, McComas DJ, Riley P, Walker RJ, Robertson P, Desai S, Clarke JT, Young DT. An auroral flare at Jupiter. Nature 2001; 410:787-9. [PMID: 11298440 DOI: 10.1038/35071018] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Jupiter's aurora is the most powerful in the Solar System. It is powered largely by energy extracted from planetary rotation, although there seems also to be a contribution from the solar wind. This contrasts with Earth's aurora, which is generated through the interaction of the solar wind with the magnetosphere. The major features of Jupiter's aurora (based on far-ultraviolet, near-infrared and visible-wavelength observations) include a main oval that generally corotates with the planet and a region of patchy, diffuse emission inside the oval on Jupiter's dusk side. Here we report the discovery of a rapidly evolving, very bright and localized emission poleward of the northern main oval, in a region connected magnetically to Jupiter's outer magnetosphere. The intensity of the emission increased by a factor of 30 within 70 s, and then decreased on a similar timescale, all captured during a single four-minute exposure. This type of flaring emission has not previously been reported for Jupiter (similar, but smaller, transient events have been observed at Earth), and it may be related directly to changes in the solar wind.
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Fu TY, Gamlin JN, Olovsson G, Scheffer JR, Trotter J, Young DT. Photochemistry of Triptycene-1,4-quinone. Acta Crystallogr C 1998. [DOI: 10.1107/s0108270197012109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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37
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Moore TE, Chappell CR, Chandler MO, Craven PD, Giles BL, Pollock CJ, Burch JL, Young DT, Waite JH, Nordholt JE, Thomsen MF, McComas DJ, Berthelier JJ, Williamson WS, Robson R, Mozer FS. High-Altitude Observations of the Polar Wind. Science 1997. [DOI: 10.1126/science.277.5324.349] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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38
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Boynton WV, D'Uston LC, Young DT, Lunine JI, Waite JH, Bailey SH, Berthelier JJ, Bertaux JL, Borrel V, Burke MF, Cohen BA, McComas DH, Nordholt JE, Evans LG, Trombka JI. The determination of ice composition with instruments on cometary landers. ACTA ASTRONAUTICA 1997; 40:663-674. [PMID: 11540784 DOI: 10.1016/s0094-5765(97)00005-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The determination of the composition of materials that make up comets is essential in trying to understand the origin of these primitive objects. The ices especially could be made in several different astrophysical settings including the solar nebula, protosatellite nebulae of the giant planets, and giant molecular clouds that predate the formation of the solar system. Each of these environments makes different ices with different composition. In order to understand the origin of comets, one needs to determine the composition of each of the ice phases. For example, it is of interest to know that comets contain carbon monoxide, CO, but it is much more important to know how much of it is a pure solid phase, is trapped in clathrate hydrates, or is adsorbed on amorphous water ice. In addition, knowledge of the isotopic composition of the constituents will help determine the process that formed the compounds. Finally, it is important to understand the bulk elemental composition of the nucleus. When these data are compared with solar abundances, they put strong constraints on the macro-scale processes that formed the comet. A differential scanning calorimeter (DSC) and an evolved gas analyzer (EGA) will make the necessary association between molecular constituents and their host phases. This combination of instruments takes a small (tens of mg) sample of the comet and slowly heats it in a sealed oven. As the temperature is raised, the DSC precisely measures the heat required, and delivers the gases to the EGA. Changes in the heat required to raise the temperature at a controlled rate are used to identify phase transitions, e.g., crystallization of amorphous ice or melting of hexagonal ice, and the EGA correlates the gases released with the phase transition. The EGA consists of two mass spectrometers run in tandem. The first mass spectrometer is a magnetic-sector ion-momentum analyzer (MAG), and the second is an electrostatic time-of-flight analyzer (TOF). The TOF acts as a detector for the MAG and serves to resolve ambiguities between fragments of similar mass such as CO and N2. Because most of the compounds of interest for the volatile ices are simple, a gas chromatograph is not needed and thus more integration time is available to determine isotopic ratios. A gamma-ray spectrometer (GRS) will determine the elemental abundances of the bulk cometary material by determining the flux of gamma rays produced from the interaction of the cometary material with cosmic ray produced neutrons. Because the gamma rays can penetrate a distance of several tens of centimeters a large volume of material is analyzed. The measured composition is, therefore, much more likely to be representative of the bulk comet than a very small sample that might have lost some of its volatiles. Making these measurements on a lander offers substantial advantages over trying to address similar objectives from an orbiter. For example, an orbiter instrument can determine the presence and isotopic composition of CO in the cometary coma, but only a lander can determine the phase(s) in which the CO is located and separately determine the isotopic composition of each reservoir of CO. The bulk composition of the nucleus might be constrained from separate orbiter analyses of dust and gas in the coma, but the result will be very model dependent, as the ratio of gas to dust in the comet will vary and will not necessarily be equal to the bulk value.
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Farrugia CJ, Young DT, Geiss J, Balsiger H. The composition, temperature, and density structure of cold ions in the quiet terrestrial plasmasphere: GEOS 1 results. ACTA ACUST UNITED AC 1989. [DOI: 10.1029/ja094ia09p11865] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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40
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Balsiger H, Altwegg K, Bühler F, Geiss J, Ghielmetti AG, Goldstein BE, Goldstein R, Huntress WT, Ip WH, Lazarus AJ, Meier A, Neugebauer M, Rettenmund U, Rosenbauer H, Schwenn R, Sharp RD, Shelley EG, Ungstrup E, Young DT. Ion composition and dynamics at comet Halley. Nature 1986. [DOI: 10.1038/321330a0] [Citation(s) in RCA: 343] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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41
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Bame SJ, Anderson RC, Asbridge JR, Baker DN, Feldman WC, Fuselier SA, Gosling JT, McComas DJ, Thomsen MF, Young DT, Zwickl RD. Comet Giacobini-Zinner: Plasma Description. Science 1986; 232:356-61. [PMID: 17792144 DOI: 10.1126/science.232.4748.356] [Citation(s) in RCA: 177] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A strong interaction between the solar wind and comet Giacobini-Zinner was observed oh 11 September 1985 with the Los Alamos plasma electron experiment on the International Cometary Explorer (ICE) spacecraft. As ICE approached an intercept point 7800 kilometers behind the nucleus from the south and receded to the north, upstream phenomena due to the comet were observed. Periods of enhanced electron heat flux from the comet as well as almost continuous electron density fluctuations were measured. These effects are related to the strong electron heating observed in the cometary interaction region and to cometary ion pickup by the solar wind, respectively. No evidence for a conventional bow shock was found as ICE entered and exited the regions of strongest interaction of the solar wind with the cometary environment. The outer extent of this strong interaction zone was a transition region in which the solar wind plasma was heated, compressed, and slowed. Inside the inner boundary of the transition region was a sheath that enclosed a cold intermediate coma. In the transition region and sheath, small-scale enhancements in density were observed. These density spikes may be due to an instability associated with cometary ion pickup or to the passage of ICE through cometary ray structures. In the center of the cold intermediate coma a narrow, high-density core of plasma, presumably the developing plasma tail was found. In some ways this tail can be compared to the plasma sheet in Earth's magnetotail and to the current sheet in the tail at Venus. This type of configuration is expected in the double-lobe magnetic topology detected at the comet, possibly caused by the theoretically expected draping of the interplanetary magnetic field around its ionosphere.
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Knott K, Fairfield D, Korth A, Young DT. Observations near the magnetopause at the onset of the July 29, 1977, sudden storm commencement. ACTA ACUST UNITED AC 1982. [DOI: 10.1029/ja087ia08p05888] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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43
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Horwitz JL, Baugher CR, Chappell CR, Shelley EG, Young DT. Conical pitch angle distributions of very low-energy ion fluxes observed by ISEE 1. ACTA ACUST UNITED AC 1982. [DOI: 10.1029/ja087ia04p02311] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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44
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Horwitz JL, Cobb WK, Baugher CR, Chappell CR, Frank LA, Eastman TE, Anderson RR, Shelley EG, Young DT. On the relationship of the plasmapause to the equatorward boundary of the auroral oval and to the inner edge of the plasma sheet. ACTA ACUST UNITED AC 1982. [DOI: 10.1029/ja087ia11p09059] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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45
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Young DT, Balsiger H, Geiss J. Correlations of magnetospheric ion composition with geomagnetic and solar activity. ACTA ACUST UNITED AC 1982. [DOI: 10.1029/ja087ia11p09077] [Citation(s) in RCA: 334] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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46
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Fennell JF, Johnson RG, Young DT, Torbert RB, Moore TE. Plasma and electric field boundaries at high and low altitudes on July 29, 1977. ACTA ACUST UNITED AC 1982. [DOI: 10.1029/ja087ia08p05933] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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47
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Roux A, Perraut S, Rauch JL, de Villedary C, Kremser G, Korth A, Young DT. Wave-particle interactions near ΩHe+observed on board GEOS 1 and 2: 2. Generation of ion cyclotron waves and heating of He+ions. ACTA ACUST UNITED AC 1982. [DOI: 10.1029/ja087ia10p08174] [Citation(s) in RCA: 213] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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48
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Horwitz JL, Baugher CR, Chappell CR, Shelley EG, Young DT. Pancake pitch angle distributions in warm ions observed with ISEE 1. ACTA ACUST UNITED AC 1981. [DOI: 10.1029/ja086ia05p03311] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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49
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Young DT, Perraut S, Roux A, de Villedary C, Gendrin R, Korth A, Kremser G, Jones D. Wave-particle interactions near ΩHe+observed on GEOS 1 and 2 1. Propagation of ion cyclotron waves in He+-rich plasma. ACTA ACUST UNITED AC 1981. [DOI: 10.1029/ja086ia08p06755] [Citation(s) in RCA: 357] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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50
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Kottke TE, Young DT, McCall MM. Effect of social class on recovery from myocardial infarction--a followup study of 197 consecutive patients discharged from hospital. MINNESOTA MEDICINE 1980; 63:590-7. [PMID: 7442630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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