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Ann. Geophys., 21, 997-1003, 2003
www.ann-geophys.net/21/997/2003/
© European Geosciences Union 2003
Observations of the spatial structure of electron precipitation pulsations using an imaging riometer
A. Senior and F. Honary
Department of Communication Systems, Lancaster University, Lancaster, LA1 4YR, UK
Abstract. Electron precipitation
can be modulated by geomagnetic pulsation activity. This can be observed as
pulsation of cosmic noise absorption as measured by riometers. Observations of
such pulsations exhibiting field-line resonance and particle-driven
characteristics using an imaging riometer are presented and the capability of
the instrument to map their spatial structure is demonstrated. It is shown that
for the events studied, the spatial variation of pulsation phase as measured by
the riometer agrees with that inferred from ground-based magnetometers, whereas
the spatial variation of pulsation amplitude may show a different structure. It
is suggested that this is consistent with the mechanism proposed by Coroniti
and Kennel (1970) where one would expect a fixed phase relationship between
magnetic and absorption pulsations, but where the amplitude of the absorption
pulsation can depend on several factors other than the amplitude of the
magnetic pulsation.
Key words. Ionosphere (ionosphere–magnetosphere
interactions; particle precipitation) – Magnetospheric physics (MHD waves and
instabilities)
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