Lecturer: Lisa Rosenqvist (IRF-Uppsala)
Date: 2005-12-21 13:15
Place: Room 80121, Ångström Laboratory, Uppsala

The impact of a strongly magnetized high speed solar wind on the Earth's magnetosphere-ionosphere system

In this thesis we study the terrestrial response of the chain of solar eruptions during late October 2003. We compare two large geomagnetic storms with respect to the characteristics of the solar eruptions, the interplanetary driver (magnetic cloud), and the resulting storm geoeffectiveness. Within the second storm some of the strongest substorms in the history of magnetic recordings were observed in northern Scandinavia. During this time, variations in the solar wind pressure can release enormous amounts of stored energy with virtually no time delay after the arrival of the disturbance at the subsolar magnetopause. The Cluster spacecraft crossed the magnetopause simultaneously with the onset of these substorm intensifications whilst the EISCAT radars and magnetometers observed the ionosphere during this sequence of events. This provides an excellent opportunity to investigate the observed energy coupling between the solar wind, magnetosphere and ionosphere system during this event. The global power input can be estimated to be between 25 and 90 TW at substorm onset using Cluster observations. About 8-19 % of this power is dissipated in the ionosphere as Joule heat according to EISCAT and AMIE estimates. Based on electrojet index-based empirical relations we find a corresponding ratio of only 3 %. In summary, it seems like the inner magnetosphere and ionosphere cannot dissipate all the energy during such strong energy input and that much of the energy is lost from the magnetosphere.

Created 2005-12-07 09:38:10 by Rick McGregor
Last changed 2005-12-07 09:38:43 by Rick McGregor