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Ann. Geophys., 24, 2169-2178, 2006
www.ann-geophys.net/24/2169/2006/
© European Geosciences Union 2006
Ionospheric signatures of the low-latitude boundary layer under conditions of northward IMF and small clock angle
S. E. Pryse1, R. W. Sims1,*, J. Moen2,**, and K. Oksavik2,***
1Institute of Mathematical and Physical Sciences, University of Wales, Aberystwyth, SY23 3BZ, UK
2University of Oslo, Blindern, Norway
*now at: Medical Physics Directorate, University Hospital of North Staffordshire, Stoke-on-Trent, UK
**also at: Arctic Geophysics, The University Centre in Svalbard, Longyearbyen, Norway
***now at: JHU/APL, Laurel, Maryland, USA
Abstract. A case study is presented that concerns the footprints of the low-latitude
boundary layer in the high-latitude ionosphere. The measurements were made
near local magnetic noon in summertime under conditions of Bz>0 and small
clock angle. Of particular interest are particle fluxes measured in the
region by the NOAA-12 satellite that revealed energetic (>30 keV)
electrons, characteristic of trapped particles, together with a population
of softer precipitating magnetosheath particles. The particle
energy-distribution was distinct from those identifying the central plasma
sheet at lower latitudes. On its poleward side the layer extended to at
least the latitude of the polar cap boundary as identified in ion flows and
electron densities measured by the EISCAT Svalbard radar. It is proposed
that the particles of the low-latitude boundary layer occurred on
newly-closed magnetic field lines, which were formed by the closure of open
polar cap field by lobe reconnection in both Northern and Southern
Hemispheres.
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