The low-latitude boundary layer: Application of ISTP advances to past data
Lockwood, M. and Hapgood, M. A. (1999) The low-latitude boundary layer: Application of ISTP advances to past data. In: Toward Solar Max 2000: The Present Achievements and Future Opportunities of ISTP and GEM, February 10-13, 1998, Yosemite Park, California, USA, pp. 103-111. (in “The Physics of Sun-Earth Plasma and Field Processes” ed. J. Burch, AGU Monograph 109, 103-111, doi: 10.1029/GM109p0103, 1999)
To link to this article DOI: 10.1029/GM109p0103
The destruction of the four Cluster craft was a major loss to the planned ISTP effort, of which studies of the magnetopause and low-latitude boundary layer (LLBL) were an important part. While awaiting the re-flight mission, Cluster-II, we have been applying advances in our understanding made using other ISTP craft (like Polar and Wind) and using ground-based facilities (in particular the EISCAT incoherent scatter radars and the SuperDARN HF coherent radars) to measurements of the LLBL made in 1984 and 1985 by the AMPTE-UKS and -IRM spacecraft pair. In particular, one unexplained result of the AMPTE mission was that the electron characteristics could, in nearly all cases, order independent measurements near the magnetopause, such as the magnetic field, ion temperatures and the plasma flow. Studies of the cusp have shown that the precipitation is ordered by the time-elapsed since the field line was opened by reconnection. This insight has allowed us to reanalyse the AMPTE data and show that the ordering by the transition parameter is also due to the variation of time elapsed since reconnection, with the important implication that reconnection usually coats most of the dayside magnetopause with at least some newly-opened field lines. In addition, we can use the electron characteristics to isolate features like RDs, slow-mode shocks and slow-mode expansion fans. The ion characteristics can be used to compute the reconnection rate. We here retrospectively apply these new techniques, developed in the ISTP era, to a much-studied flux transfer event observed by the AMPTE satellites. As a result, we gain new understanding of its cause and structure.