Cluster magnetic field observations of magnetospheric boundaries
Balogh, A.; Horbury, T. S.; Lucek, E. A.; Dunlop, M. W.; Carr, C.; Brown, P.; Cargill, P. J.; Georgescu, E.; Fornaçon, K. -H.; Oddy, T.
United Kingdom, Germany
Abstract
Early Cluster magnetic field observations of boundaries and boundary layers in the near-Earth environment are reviewed. By combining data from four spacecraft, typically separated by ∼600 km, the scale, orientation and motion of structures can be deduced. Early results from the magnetic field investigation are reviewed, such as estimates of the orientation and motion of the magnetopause, including an inward velocity of 125 km s-1 in response to an interplanetary shock; evidence that crossings of the magnetopause are due to its inward and outward motion, rather than structures propagating along it; simultaneous flux transfer event signatures on both sides of the magnetopause; field-aligned currents and small scale structure in the mid-altitude cusp; variable motion of the high-altitude cusp; and the scale and orientation of mirror mode structures in the magnetosheath.