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Detailed Reference Information |
Fuselier, S.A. and Anderson, B.J. (1996). Low-energy He+ and H+ distributions and proton cyclotron waves in the afternoon equatorial magnetosphere. Journal of Geophysical Research 101: doi: 10.1029/96JA00292. issn: 0148-0227. |
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Characteristics of low energy (~10 to 50 eV) H+ and He+ distributions in the afternoon magnetosphere from L=4 to 9 are studied using Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE) data. He+ distributions in this study routinely display features indicating resonant heating by proton cyclotron waves in the outer magnetosphere (L>7) whereas protons exhibit minimal evidence of heating. Low energy H+ distributions have T⊥≫T∥ for L7. The change is due to a decrease in T⊥ with increasing L and is consistent with adiabatic cooling in the perpendicular direction as the ions convect sunward. By contrast, low-energy He+ distributions have T⊥≫T∥ independent of L. The failure of the He+ to cool adiabatically indicates that He+ experiences transverse heating as it convects sunward through the outer magnetosphere. The occurrence of proton cyclotron waves in the afternoon magnetosphere is evaluated using AMPTE/CCE magnetometer data and shows that low energy ions convecting sunward from the afternoon plasmasphere have a 20% chance of being exposed to cyclotron waves by the time they reach L=5,50% by L=6 and >95% by L=7. The majority of cyclotron waves in the early afternoon outer magnetosphere occur above the local He+ gyrofrequency and will interact resonantly with He+ but nonresonantly with H+. The combined effects of adiabatic sunward convection and interactions between the low-energy ions and proton cyclotron waves therefore account for the observed characteristics of both the H+ and He+ distributions in the afternoon magnetosphere. ¿ American Geophysical Union 1996 |
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Abstract |
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Keywords
Magnetospheric Physics, Magnetospheric configuration and dynamics, Magnetospheric Physics, Plasma waves and instabilities, Space Plasma Physics, Charged particle motion and acceleration, Space Plasma Physics, Wave/particle interactions |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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