Abstract
Lobe cell convection and polar cap precipitation
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
Space Sciences Laboratory, University of California, Berkeley, California, USA
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
Space Sciences Laboratory, University of California, Berkeley, California, USA
Space Sciences Laboratory, University of California, Berkeley, California, USA
Space Sciences Laboratory, University of California, Berkeley, California, USA
The characteristic electric and magnetic field signature of lobe cells as observed by the low-altitude FAST satellite in 55
dawn-dusk passes are compared with Polar ultraviolet images of polar cap auroral activity. Initial results from 34 events
of UV image coverage suggest that there is an intimate coupling between the sunward convection flow of the lobe cell and transpolar
auroral arcs or diffuse polar cap precipitation in ∼62% of these cases. However, in some cases where the field signatures
are suggestive of lobe cell convection, there is no detectable particle precipitation either in Polar UVI or the FAST data
sets. Moreover, the presence of lobe cells coincide with UV data intensifications in the premidnight 2000–2400 MLT sector
and/or the postnoon 1500 MLT region in ∼59% of all cases with UVI coverage. The magnetic local time dependence of the lobe
cells and polar cap precipitation on the interplanetary magnetic field (IMF) are examined using the upstream Wind monitor.
The relative importance of the IMF B
y
and B
z
components are investigated and compared with the predictions of the antiparallel merging model and strongly suggests a connection
with the magnetospheric sash, as is further implied by the mapping of magnetic field lines using the
Received 4 October 2002; accepted 7 January 2003; published 17 May 2003.
Citation: (2003), Lobe cell convection and polar cap precipitation, J. Geophys. Res., 108(A5), 1198, doi:10.1029/2002JA009725.
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