Penetration of the interplanetary field B{sub y} and magnetosheath plasma into the magnetosphere: Implications for the predominant magnetopause merging site

Journal Article · Sun Jan 01 04:00:00 EST 1995 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/94JA02632· OSTI ID:96419

Newell, P T; Sibeck, D G; Meng, C I ^[1]

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1. Johns Hopkins Univ., Laurel, MD (United States)

Magnetosheath plasma penetrates into the magnetosphere creating the particle cusp, and similarly the interplanetary magnetic field (IMF) B{sub y} component penetrates the magnetopause. The authors reexamine the phenomenology of such penetration to investigate implications for the magnetopause merging site. Three models are popular: (1) the {open_quotes}antiparallel{close_quotes} model, in which merging occurs where the local magnetic shear is largest (usually high magnetic latitudes); (2) a tilted merging line passing through the subsolar point but extending to very high latitudes; or (3) a tilted merging line passing through the subsolar point in which most merging occurs within a few Earth radii of the equatorial plane and local noon (subsolar merging). It is difficult to distinguish between the first two models, but the third implies some very different predictions. The authors show that properties of the particle cusp imply that plasma injection into the magnetosphere occurs most often at high magnetic latitudes. In particular, they note the following: (1) The altitude of the merging site inferred from midlatitude cusp ion pitch angle dispersion is typically 8-12 R{sub E}. (2) The highest ion energy observable when moving poleward through the cusp drops long before the bulk of the cusp plasma is reached, implying that ions are swimming upstream against the sheath flow shortly after merging. (3) Low-energy ions are less able to enter the winter cusp than the summer cusp. (4) The local time behavior of the cusp as a function of B{sub y} and B{sub z} corroborates predictions of the high-latitude merging models. They also reconsider the penetration of the IMF B{sub y} component onto closed dayside field lines. Our approach, in which closed field lines move to fill in flux voids created by asymmetric magnetopause flux erosion, shows that strict subsolar merging cannot account for the observations. 42 refs., 5 figs.

• OSTI ID: 96419
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A1 Vol. 100; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
EARTH MAGNETOSPHERE
INTERPLANETARY MAGNETIC FIELDS
MAGNETIC RECONNECTION
MAGNETOPAUSE
MAGNETOSHEATH
POLAR CUSP