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Title: Energetic particle perspective of the magnetopause

Abstract

We present a detailed analysis of energetic (>24 keV) particle data obtained from the Isee satellites during a series of magnetopause crossings which occurred at 0000--0400 hours UT (approx.1030 hours LT) on November 20, 1977. The primary energetic particle data used are the three-dimensional distributions obtained from the Isee A satellite. Correlative magnetic field measurements are used to relate the particle behavior to magnetic field characteristics at and earthward of the magnetopause. We find that to first order the magnetopause can be regarded as a perfectly absorbing boundary for trapped >24-keV particles, that it is nearly alway in motion, and that boundary waves are often present. We find that the observed dayside magnetopause motion is consistent with a large-scale radial motion having an approx.10-min period plus superimposed boundary waves with a 90- to 150-s period. More qualitatively, we find that the data require a third and longer period (approx. 30 min) magnetopause motion upon which the above, shorter-period motions are superimposed. It is concluded that the radial gradient to the magnetopause observed in the directional, >24-keV, dayside, near-equatorial, magnetospherically trapped particle flux is due to internal magnetospheric processes. Just outside the magnetopause in the magnetosheath we observe a broad (approximatelymore » hemispherical) field-aligned flow of >24-keV ions away from the magnetosphere. The absolute intensity and spectral characteristics of this flow and its reltion to the magnetopause and the trapped particle population indicate that it is formed by the leakage of trapped particles from the radiation belts onto magnetosheath field lines as their trajectories move to within two gyroradii of the magnetopause.« less

Authors:
; ; ;
Publication Date:
Research Org.:
NOAA Space Environment Laboratory, Boulder, Colorado 80303
OSTI Identifier:
5613940
Resource Type:
Journal Article
Journal Name:
J. Geophys. Res.; (United States)
Additional Journal Information:
Journal Volume: 84:A11
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; MAGNETOPAUSE; TRAPPING; ENERGY SPECTRA; GEOMAGNETIC FIELD; IONS; MAGNETOSHEATH; RADIATION BELTS; CHARGED PARTICLES; MAGNETIC FIELDS; SPECTRA; 640203* - Atmospheric Physics- Magnetospheric Phenomena- (-1987)

Citation Formats

Williams, D J, Fritz, T A, Wilken, B, and Keppler, E. Energetic particle perspective of the magnetopause. United States: N. p., 1979. Web. doi:10.1029/JA084iA11p06385.
Williams, D J, Fritz, T A, Wilken, B, & Keppler, E. Energetic particle perspective of the magnetopause. United States. doi:10.1029/JA084iA11p06385.
Williams, D J, Fritz, T A, Wilken, B, and Keppler, E. Thu . "Energetic particle perspective of the magnetopause". United States. doi:10.1029/JA084iA11p06385.
@article{osti_5613940,
title = {Energetic particle perspective of the magnetopause},
author = {Williams, D J and Fritz, T A and Wilken, B and Keppler, E},
abstractNote = {We present a detailed analysis of energetic (>24 keV) particle data obtained from the Isee satellites during a series of magnetopause crossings which occurred at 0000--0400 hours UT (approx.1030 hours LT) on November 20, 1977. The primary energetic particle data used are the three-dimensional distributions obtained from the Isee A satellite. Correlative magnetic field measurements are used to relate the particle behavior to magnetic field characteristics at and earthward of the magnetopause. We find that to first order the magnetopause can be regarded as a perfectly absorbing boundary for trapped >24-keV particles, that it is nearly alway in motion, and that boundary waves are often present. We find that the observed dayside magnetopause motion is consistent with a large-scale radial motion having an approx.10-min period plus superimposed boundary waves with a 90- to 150-s period. More qualitatively, we find that the data require a third and longer period (approx. 30 min) magnetopause motion upon which the above, shorter-period motions are superimposed. It is concluded that the radial gradient to the magnetopause observed in the directional, >24-keV, dayside, near-equatorial, magnetospherically trapped particle flux is due to internal magnetospheric processes. Just outside the magnetopause in the magnetosheath we observe a broad (approximately hemispherical) field-aligned flow of >24-keV ions away from the magnetosphere. The absolute intensity and spectral characteristics of this flow and its reltion to the magnetopause and the trapped particle population indicate that it is formed by the leakage of trapped particles from the radiation belts onto magnetosheath field lines as their trajectories move to within two gyroradii of the magnetopause.},
doi = {10.1029/JA084iA11p06385},
journal = {J. Geophys. Res.; (United States)},
number = ,
volume = 84:A11,
place = {United States},
year = {1979},
month = {11}
}