IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS011 Poster presentation 2147
3-D geomagnetic impulses: Synopsis of field components at the CMB
Dr. Ludwig Ballani
Geodesy and Remote Sensing GeoForschungsZentrum Potsdam (GFZ) IAG
Hans Greiner-Mai, Dietrich Stromeyer, Ingo Wardinski, Jan Hagedoorn, Aude
Chambodut
Geomagnetic impulses ('jerks') were discovered at first in one field quantity: the dY/dt secular variation
component. Because of the integral 3-D character of the field, every episodic process affects all the
three field components, however often in a different way. Thus, for a comprehensive description of such
processes, which give important hints for the investigation of the core-mantle boundary region, all field
components should be checked commonly. We analyse several global data sets within the time span
1980-2000 with respect to the occurence of geomagnetic impulses (around the year 1991) in the single
components. We study their mutual correlations, and try to clarify its common (vecorial) structure at the
earth surface. Utilising these findings and assuming a mantle conductivity model (radially dependent,
weak conducting and bordered by a high-conductive base layer) in a second step, we apply the nonharmonic
downward continuation method to track and to analyse the distribution of geomagnetic
impulses for all single field components at the CMB where they appear at an earlier stage as seen at the
earth surface. Subsequently, we merge the different components for a synoptical vectorial view of the
impulses found. The results of these determinations, which include the effect of a conducting mantle for
the first time, mark only an initial step. Further decompositions of the space-time behavior of the
vectorial impulse will be necessary to understand in more detail the physical mechanism behind.
Keywords: jerk, magnetic field components, core mantle boundary