Geoscience Reference
In-Depth Information
Chapter 4
Electromagnetic Drivers in the Upper
Atmosphere: Observations and Modeling
A.A. Namgaladze, M. F orster, B.E. Prokhorov, and O.V. Zolotov
Abstract
This chapter presents and discusses some of the most recent mea-
surements obtained by the Electron Drift Instrument (EDI) on “Cluster”, the
accelerometer on board the low-Earth-orbiting satellite CHAMP, and global maps
of total electron content (TEC) gathered by the fleet of GPS satellites. It aims
at a better understanding of the globally interconnected complex plasma physical
and electrodynamic processes of the Earth's upper atmosphere by means of first-
principle numerical modeling using the Upper Atmosphere Model (UAM). The
study results show ionospheric electric fields, generated by magnetospheric and
seismogenic sources, and reveal their influence on the thermospheric dynamics
and the TEC pattern. UAM simulations of the thermospheric neutral wind at
high latitudes are compared with CHAMP observations for varying interplanetary
magnetic field (IMF) conditions on 28 October 2003, the day before the famous
Halloween superstorm of the previous solar cycle. The simulations show the
immediate response of the upper atmosphere and its high sensitivity to IMF
changes in strength and orientation. Investigation of the 'lithosphere-atmosphere-
ionosphere' coupling problem allowed statistically describing GPS-measured TEC
variations treated as precursors to earthquakes as (1) anomalous strong (30-90% and
more) TEC-positive or -negative deviations relative to the quiet conditions before
the forthcoming seismic event, not less than M5 by magnitude, linked to the near-
