Average motion, structure and orientation of the distant magnetotail determined from remote sensing of the edge of the plasma sheet boundary layer with E > 35 keV ions

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

DOI:https://doi.org/10.1029/94JA02417· OSTI ID:96418

Owen, C J; Slavin, J A; Richardson, I G ^[1]; Murphy, N ^[2]; Hynds, R J ^[3]

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1. NASA Goddard Space Flight Center, Greenbelt, MD (United States)
2. California Institute of Technology, Pasadena, CA (United States)
3. Imperial College of Science, London (United Kingdom)

In this paper, the authors study gradients of the energetic ion intensity observed at the edge of the plasma sheet boundary layer (PSBL) by the energetic ion anisotropy spectrometer (EPAS) on ISEE 3. In particular, they have determined the velocity of the boundary relative to the spacecraft in the direction perpendicular to the tail axis and the angle which the boundary normal makes to the spacecraft spin axis for 1160 PSBL encounters at X{sub GSM}>{minus}240 R{sub E}. By assuming that, on average, the edge of the PSBL is parallel to the cross-tail current sheet, they are then able to determine a number of properties of the structure, orientation and motion of the deep geomagnetic tail. They conclude the following: (1) Most crossings of the edge of the PSBL are caused by transverse motion of the entire tail induced by solar wind direction variations. (2) The typical velocity of the PSBL in a direction perpendicular to the tail axis is 50-85 km s{sup {minus}1}. (3) The average twist of the tail is near zero, with the edge of the PSBL lying parallel to the ecliptic plane. (4) The width of the distribution decreases with downtail distance. (5) The variation of the distributions with cross-tail position reveals that this decrease in width is most likely due to the edge of the PSBL being concave, or significantly flared at the tail flanks, in the near-Earth region. (6) During days on which the IMF has {open_quotes}away{close_quotes} sector structure, the north lobe of the tail is twisted on average towards dawn by 7.0{+-}2.4{degrees}. (7) During days on which the IMF has {open_quotes}toward{close_quotes} sector structure, the north lobe is tilted toward dusk by 3.8{+-}2.3{degrees}. (8) The distribution of tail twists is wider for lower levels of geomagnetic activity, indicating that the tail is able to twist more at lower levels of activity. (9) The data set reveals no evident effect of the Earth`s dipole wobble. 108 refs., 14 figs., 2 tabs.

• OSTI ID: 96418
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: 1A1 Vol. 100; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BOUNDARY LAYERS
MAGNETOTAIL
MOTION
ORIENTATION
REMOTE SENSING