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Ann. Geophys., 23, 1867-1880, 2005
www.ann-geophys.net/23/1867/2005/
© European Geosciences Union 2005
A case study testing the cavity mode model of the magnetosphere
D. V. Sarafopoulos
Department of Electrical and Computer Engineering, Demokritos University of Thrace, Xanthi, Greece
Abstract. Based on a case study we test the cavity mode model of the
magnetosphere, looking for eigenfrequencies via multi-satellite and
multi-instrument measurements. Geotail and ACE provide information on the
interplanetary medium that dictates the input parameters of the system; the
four Cluster satellites monitor the magnetopause surface waves; the POLAR
(L=9.4) and LANL 97A (L=6.6) satellites reveal two in-situ monochromatic
field line resonances (FLRs) with T=6 and 2.5 min, respectively; and the
IMAGE ground magnetometers demonstrate latitude dependent delays in
signature arrival times, as inferred by Sarafopoulos (2004b). Similar
dispersive structures showing systematic delays are also extensively
scrutinized by Sarafopoulos (2005) and interpreted as tightly associated
with the so-called pseudo-FLRs, which show almost the same observational
characteristics with an authentic FLR. In particular for this episode,
successive solar wind pressure pulses produce recurring ionosphere twin
vortex Hall currents which are identified on the ground as pseudo-FLRs. The
BJN ground magnetometer records the pseudo-FLR (alike with the other IMAGE
station responses) associated with an intense power spectral density ranging
from 8 to 12 min and, in addition, two discrete resonant lines with T=3.5
and 7 min. In this case study, even though the magnetosphere is evidently
affected by a broad-band compressional wave originated upstream of the bow
shock, nevertheless, we do not identify any cavity mode oscillation within
the magnetosphere. We fail, also, to identify any of the
cavity mode frequencies proposed by Samson (1992).
Keywords. Magnetospheric physics (Magnetosphereionosphere
interactions; Solar wind-magnetosphere interactions;
MHD waves and instabilities)
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