Journal article
Solar wind control of the polar cusp at high altitude
Journal of geophysical research, Vol.105(A1), pp.245-251
2000
DOI: 10.1029/1999JA900412
Abstract
The POLAR mission is ideally suited to study the high-altitude polar cusp. Polar magnetometer data, together with electron and ion measurements from the Hydra and Toroidal Imaging Mass-Angle Spectrograph (Timas) instruments from March 1996 to December 1997, have been used to identify 459 polar cusp crossings. These crossings are used to study the statistical behavior of the cusp location and its dependence on the solar wind conditions. We find that the invariant latitude of the center of the cusp varies from 70° to 86° as solar wind conditions change and the magnetic local time of the footprints of the cusp magnetic field lines extends from 0800 to 1600 MLT, the cusp being slightly wider for increasing solar wind dynamic pressure. The average latitude of the center of the cusp is at 80.3° invariant latitude at noon and decreases to 78.7° at 0800 and 1600 MLT. The cusp also appears to thicken slightly in invariant latitude with increasing dynamic pressure. The center of the cusp moves equatorward with increasingly southward interplanetary magnetic field (IMF) to 73° invariant latitude for a 10 nT southward IMF. The cusp moves only slightly for northward IMF. This motion is consistent with erosion of dayside magnetic flux for southward IMF but little or no erosion for northward IMF. The cusp is also somewhat wider in invariant latitude with increasingly northward IMF. Consistent with low-altitude observations, we find that there is a clear MLT shift due to the IMF By for strongly southward IMF. We interpret the motion of the local time of the cusp for southward IMF as a shift of the reconnection site away from the noon meridian when the IMF is not due southward.
Details
- Title: Subtitle
- Solar wind control of the polar cusp at high altitude
- Creators
- X. W Zhou - University of California, Los AngelesC. T Russell - Institute of Geophysics and Planetary Physics, University of California, Los Angeles, United StatesG LE - Institute of Geophysics and Planetary Physics, University of California, Los Angeles, United StatesS. A Fuselier - Lockheed MartinJ. D Scudder - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research, Vol.105(A1), pp.245-251
- Publisher
- American Geophysical Union
- DOI
- 10.1029/1999JA900412
- ISSN
- 0148-0227
- eISSN
- 2156-2202
- Language
- English
- Date published
- 2000
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199675802771
Metrics
3 Record Views