Förslaget inkom 2006-09-28
Induced electric fields in the Earths magnetosphere
OBS! ANSÖKNINGSTIDEN FÖR DETTA EXJOBB HAR LÖPT UT.
The Sun emits a continuous wind of plasma, the solar wind. When this wind reaches the Earth it interacts with the geomagnetic field, setting up a cavity known as the magnetosphere. The solar wind is quite dynamic, both density and velocity can change significantly on short time scales. As a consequence of this the shape of the magnetosphere is also dynamic. Faradays law of induction relates the rate of change in a magnetic field to the curl of the local electric field. Thus, reconfiguration of the magnetospheric magnetic field is associated with induced electric fields. Depending on the location and orientation of the induced electric fields they may accelerate charged particles in the magnetosphere, possibly related to auroral emissions in the upper atmosphere. As a zeroth approximation, the induced electric field may be assumed to propagate instantly, simplifying the mathematical description. In more realistic approximations, the finite speed of propagation in the system needs to be taken into account. Because of the presence of a magnetospheric plasma, the field changes may propagate at the Alfvén velocity rather than at the velocity of light.
The project consists of several parts. First, the induced electric fields, assuming instant propagation, shall be calculated from a solar wind dependent (and thus implicity time dependent) model of the magnetospheric magnetic field, for a variety of realistic time dependencies. Then, the validity of this simple model shall be evaluated, for example by comparison with analytical solutions and numerical experiments in idealized geometries. Also comparisons to satellite data may be used. Finally, time permitting, more realistic assumptions regarding the propagation of information in the system could be analyzed, in idealized and/or realistic geometries.