Low-latitude boundary layer near noon: An open field line model

Technical Report · Sat Oct 01 04:00:00 EDT 1994

OSTI ID:102027

Lyons, L R; Schulz, M; Pridmore-Brown, D C; Roeder, J L

The authors 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 and 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, they 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, the authors 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. They also find important variations and hemispherical differences in that the size of the LLBL should depend strongly upon the x component of the IMF. This prediction is observationally testable. Finally, they 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).

• Research Organization: Aerospace Corp., Los Angeles, CA (United States)
• OSTI ID: 102027
• Report Number(s): ATR--93(7270)-1; CNN: NSF ATM-91-20072
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BOUNDARY LAYERS
EARTH MAGNETOSPHERE
GEOMAGNETIC FIELD
INTERPLANETARY MAGNETIC FIELDS
MAGNETOPAUSE
MAGNETOSHEATH
MATHEMATICAL MODELS
POLAR CUSP
PROTONS