Observations of plasmas and magnetic fields in Earth`s distant magnetotail: Comparison with a global MHD model

Journal Article · Sun Oct 01 04:00:00 EDT 1995 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/95JA00571· OSTI ID:227123

Frank, L A; Paterson, W R; Ackerson, K L ^[1]

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1. Univ. of Iowa, Iowa City, IA (United States); and others

The authors are reporting the first direct comparison of in situ observations of plasmas and magnetic fields in Earth`s distant magnetotail with the results of a time-dependent, global magnetohydrodynamic (MHD) simulation of the interaction of the solar wind with the magnetosphere. The magnetotail observations were taken with the Geotail spacecraft during the period 0300-0630 UT on October 27, 1992 at a position near the dawnside magnetopause at a downstream distance of about 81 R{sub E}. During this period a dense, cold ion stream similar in density and speed to that expected for the magnetosheath plasmas was intermittently observed. The dense, cold ion stream differed from that expected for the magnetosheath in the Y and Z components of ion bulk flow and in the Y component of the magnetic field. Simultaneous observations of the solar wind ions and the interplanetary magnetic field (IMF) with the IMP 8 spacecraft upstream from Earth provided the driving input for a global MHD model. The solar wind ion flow was steady during this period, and the IMF exhibited a series of rotations from northward to duskward. The dynamics of the magnetotail were controlled by the Y and Z components of the IMF. When this By was strongly positive, the magnetotail lobe appeared at the downstream Geotail position. Examination of the modeled plasma parameters in the Y-Z plane through the spacecraft position shows that this By provides a torque on the magnetotail about its central axis. The temporal variations of modeled parameters, i.e., ion densities, temperatures, and bulk flow velocities and the magnetic field components, are directly compared with the Geotail measurements. This first comparison of the Geotail observations with the modeled plasma parameters and magnetic field provides substantial encouragement that a global MHD model can provide a valid description of important aspects of the large-scale topology and dynamics of the magnetotail. 48 refs., 11 figs.

• OSTI ID: 227123
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A10 Vol. 100; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
COUPLING
EARTH MAGNETOSPHERE
GLOBAL ASPECTS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MAGNETOTAIL
PLASMA DRIFT
REMOTE SENSING
SIMULATION
SOLAR WIND