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Observations of Energetic Electrons (E ≳ 200 keV) in the Earth's Magnetotail: Plasma Sheet and Fireball Observations

Baker, D. N. and Stone, E. C. (1977) Observations of Energetic Electrons (E ≳ 200 keV) in the Earth's Magnetotail: Plasma Sheet and Fireball Observations. Journal of Geophysical Research A, 82 (10). pp. 1532-1546. ISSN 0148-0227. doi:10.1029/JA082i010p01532.

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With the California Institute of Technology electron/isotope spectrometer (EIS) aboard the earth-orbiting spacecraft Imp 8, intense energetic electron events (E ≳ 200 keV) have been observed at ∼30 R_E in the magnetotail on 13 of 28 magnetotail passes. In one class of events, peak absolute intensities j(E ≳ 200 keV) = 10^³–10^4 el (cm^² s sr)^(−1) are detected; the differential energy spectra for these events are very steep, with power law indices of ∼7. For this class of observations, symmetric electron pitch angle distributions are detected with the presence of little or no unidirectional streaming, a finding consistent with quasi-trapped motion of the particles. Concurrent observations with other instrumentation on the same spacecraft indicate that the local magnetic fields possess northward components while simultaneous plasma (50 eV ≤ E ≤ 45 keV) data show bulk flow speeds of a few hundred kilometers per second or less, with intense plasma heating ordinarily occurring. A second distinct class of events corresponds to lower average absolute electron intensities (E ≳ 200 keV), typically harder electron energy spectra, and strong intermittent field-aligned (and tailward) unidirectional streaming of the energetic electrons. During periods when this class of events is observed in the plasma sheet, strong southward components are found in the local magnetic fields, and large tailward bulk plasma flow has been reported (with tailward jetting in excess of 1000 km s^(−1) in certain cases). The second class of events is consistent with energetic electron motion on essentially open field lines. These streaming events are found to be associated with apparent localized acceleration regions in the magnetotail.

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Stone, E. C.0000-0002-2010-5462
Additional Information:© 1977 by the American Geophysical Union. Manuscript Accepted: 14 Jan 1977. Manuscript Received: 22 Oct 1976. We thank L. A. Frank both for providing us with the extensive set of Imp 8 Lepedea energy-time spectrograms used in this study prior to their publication and for many helpful and informative discussions. We are grateful to R. P. Lepping and N. F. Ness for providing us with the Imp 8 magnetometer data through J. H. King of the National Space Science Data Center. We also thank R. E. Vogt, who has been closely involved in this investigation, and W. E. Althouse, G. J. Hurloral, J. E. Lupton, and R. A. Mewaldt, who made significant contributions to various phases of this program. This work was supported in part by the National Aeronautics and Space Administration under contract NAS5-11066 and grant NGR 05-002-160. The Editor thanks T. P. Armstrong and R. P. Lin for their assistance in evaluating this paper.
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NASANGR 05-002-160
Issue or Number:10
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Official Citation:Baker, D. N., and E. C. Stone (1977), Observations of energetic electrons (E ≳ 200 keV) in the Earth's magnetotail: Plasma sheet and Fireball observations, J. Geophys. Res., 82(10), 1532–1546, doi:10.1029/JA082i010p01532.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43659
Deposited By: Ruth Sustaita
Deposited On:04 Feb 2014 23:44
Last Modified:10 Nov 2021 16:41

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