In:
Journal of Geophysical Research: Space Physics, American Geophysical Union (AGU), Vol. 105, No. A10 ( 2000-10), p. 23221-23238
Abstract:
We report comprehensive statistical results for 4 years of Hawkeye observations totaling 1757 boundary crossings. Our objective is to use the full set of Hawkeye plasma, magnetic field, and plasma wave data to identify every cusp‐associated data interval (entry layer, cusp, plasma mantle), to spatially map these regions, and to isolate the primary variables affecting their occurrence frequency and location. We find that SM coordinates best order the angular position of cusp region data intervals and that GSM coordinates are better for ordering in radial distance, especially for the plasma mantle. Dipole tilt and external pressure are the primary variables affecting high‐latitude and high‐altitude boundary configuration. Compared to these, the effects of IMF parameters are minor although discernable when adequate corrections are made for dipole tilt and pressure. New results on cusp flaring and indentation of the high‐latitude boundary are obtained by limiting this data set in pressure, varying dipole tilt ranges, and examining changes in boundary configuration in both SM and GSM coordinates. We find that as the dipole tilts more toward the oncoming magnetosheath plasma flow, indentation becomes enlarged and the cusp outflow region, the plasma mantle, becomes more flared out relative to the Earth‐Sun line. In contrast, as the dipole tilts away from the Sun direction, cusp indentation is reduced but the cusp outflow region remains flared out compared to boundary shapes inferred from low‐latitude observations. A semiempirical magnetopause model by Boardsen et al. [this issue] compares very well with the high‐latitude boundary layer observations reported here including a test for hemispheric symmetry, which is assumed by the model.
Type of Medium:
Online Resource
ISSN:
0148-0227
DOI:
10.1029/1999JA900269
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
2000
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