Mass Density at L=2.5 During a Magnetic Storm: a Case Study

F.W. Menk and M.A. Clilverd


The inner magnetosphere plasma environment is rather dynamic
and of great interest. Observational data usually come from
spacecraft (e.g. particle counters, imagers) and ground-based
(VLF whistlers) techniques. However, VLF receivers can also be
used to monitor artificially produced whistler-mode waves that
propagate in field-aligned ducts and that provide information on
the electron density in the equatorial plane. Furthermore, ground
magnetometers can be used to detect ULF field line resonances
(FLRs) whose frequency relates to the plasma mass density in the
equatorial plane. We describe an experiment using co-located
magnetometers and VLF receivers to monitor mass and electron
density for the same L=2.5 flux tube. We focus in particular on
the variation in electron and mass density during a magnetic
storm cycle. The experiments provide information on the storm-
time variation in heavy ion mass loading that is compared with in
situ measurements and EUV images of the He+ concentration.

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Presentation, Fall A.G.U. Meeting, San Francisco, CA, 13-17 December 2004