Ionospheric signatures of plasma injections in the cusp triggered by solar wind 
pressure pulses

Jean-Claude Cerisier, Aurelie Marchaudon, Jean-Michel Bosqued, 
Kathryn McWilliams, Harald U. Frey, Mehdi Bouhram, Harri Laakso, Malcolm Dunlop, 
Matthias Forster, and Andrew Fazakerley


We describe coordinated observations made on 14 July 2001 simultaneously in the
midaltitude cusp by Cluster and at the cuspÕs ionospheric magnetic footprint by
Super Dual Auroral Radar Network (SuperDARN) and Imager for 
Magnetopause-to-Aurora Global Exploration (IMAGE) during a period of three
successive solar wind dynamic pressure pulses. In association with each of these
pulses, Cluster observes plasma injections while auroral images from the IMAGE
spacecraft show enhanced precipitation in the cusp. Following these plasma
injections, channels of fast convection flows are observed in the ionosphere by
the SuperDARN radars. On the basis of the spatial and temporal relationships
between these various signatures, we analyze the response of the dayside
magnetosphere and ionosphere to the pressure pulses as follows: (1) the solar
wind dynamic pressure pulses are the drivers of plasma injections from the
magnetosheath into the cusp; (2) the ionospheric convection bursts start shortly
after the auroral intensifications and their duration is much longer (10 min
versus 4Ð6 min for the auroral intensifications); (3) the convection bursts
occur on the poleward side of the cusp precipitation; and (4) the Alfve«n waves
that are responsible of the transmission of the magnetic stress from the
reconnection site to the ionosphere are strongly reflected in the upper
ionosphere. This, in addition to possible parallel potential drops, may explain
the imperfect mapping of the magnetospheric electric field into the ionosphere
during the injections. These observations demonstrate that the convection bursts
are ÔÔfossilÕÕ signatures of the compressionÐinjection process, which is also a
signature of reconnection at the dayside magnetopause driven by the
interplanetary magnetic field alone.

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Journal of Geophysical Research, 110, A08204, doi:10.1029/2004JA010962, 2005