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Low-latitude boundary layer near noon: An open field line modelWe propose that many features of the cusp and low-latitude boundary layer (LLBL) observed near noon MLT can be explained by interpreting the LLBL as being on open lines with an inner boundary at the separatrix between open and closed magnetic field lines. This interpretation places the poleward boundary of the LLBL and equatorward boundary of the cusp along the field line that bifurcates at the cusp neutral point. The interpretation accounts for the abrupt boundary of magnetosheath particles at the inner edge of the LLBL, a feature that is inconsistent with LLBL formation by diffusion onto closed field lines, and for the distribution of magnetosheath particles appearing more as one continuous region than as two distinct regions across the noon cusp/LLBL boundary. Furthermore, we can explain the existence of energetic radiation belt electrons and protons with differing pitch angle distributions within the LLBL and their abrupt cutoff at the poleward boundary of the LLBL. By modeling the LLBL and cusp region quantitatively, we can account for a hemispherical difference in the location of the equatorial boundary of the cusp that is observed to be dependent on the dipole tilt angle but not on the interplanetary magnetic field (IMF) x component. We also find important variations and hemispherical differences in that the size of the LLBL that should depend strongly upon the x component of the IMF. This prediction is observationally testable. Finally, we find that when the IMF is strongly northward, the LLBL may include a narrow region adjacent to the magnetopause where field lines are detached (i.e., have both ends connected to the IMF).
Document ID
19950057067
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lyons, L. R.
(Space and Environment Technology Center Los Angeles, CA, United States)
Schulz, M.
(Space and Environment Technology Center Los Angeles, CA, United States)
Pridmore-Brown, D. C.
(Space and Environment Technology Center Los Angeles, CA, United States)
Roeder, J. L.
(Space and Environment Technology Center Los Angeles, CA, United States)
Date Acquired
August 16, 2013
Publication Date
September 1, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: A9
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A88666
Funding Number(s)
CONTRACT_GRANT: NAG5-1541
CONTRACT_GRANT: NSF ATM-91-20072
Distribution Limits
Public
Copyright
Other

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